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Alabi A, Vanderelst D, Minai AA. Rapid learning of spatial representations for goal-directed navigation based on a novel model of hippocampal place fields. Neural Netw 2023; 161:116-128. [PMID: 36745937 DOI: 10.1016/j.neunet.2023.01.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 12/16/2022] [Accepted: 01/11/2023] [Indexed: 01/21/2023]
Abstract
The discovery of place cells and other spatially modulated neurons in the hippocampal complex of rodents has been crucial to elucidating the neural basis of spatial cognition. More recently, the replay of neural sequences encoding previously experienced trajectories has been observed during consummatory behavior-potentially with implications for rapid learning, quick memory consolidation, and behavioral planning. Several promising models for robotic navigation and reinforcement learning have been proposed based on these and previous findings. Most of these models, however, use carefully engineered neural networks, and sometimes require long learning periods. In this paper, we present a self-organizing model incorporating place cells and replay, and demonstrate its utility for rapid one-shot learning in non-trivial environments with obstacles.
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Affiliation(s)
- Adedapo Alabi
- Department of Electrical & Computer Engineering, University of Cincinnati, Cincinnati, OH, 45221, USA.
| | - Dieter Vanderelst
- Department of Electrical & Computer Engineering, University of Cincinnati, Cincinnati, OH, 45221, USA.
| | - Ali A Minai
- Department of Electrical & Computer Engineering, University of Cincinnati, Cincinnati, OH, 45221, USA.
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2
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Kumar A, Barkai E, Schiller J. Plasticity of olfactory bulb inputs mediated by dendritic NMDA-spikes in rodent piriform cortex. eLife 2021; 10:70383. [PMID: 34698637 PMCID: PMC8575458 DOI: 10.7554/elife.70383] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 10/25/2021] [Indexed: 11/19/2022] Open
Abstract
The piriform cortex (PCx) is essential for learning of odor information. The current view postulates that odor learning in the PCx is mainly due to plasticity in intracortical (IC) synapses, while odor information from the olfactory bulb carried via the lateral olfactory tract (LOT) is ‘hardwired.’ Here, we revisit this notion by studying location- and pathway-dependent plasticity rules. We find that in contrast to the prevailing view, synaptic and optogenetically activated LOT synapses undergo strong and robust long-term potentiation (LTP) mediated by only a few local NMDA-spikes delivered at theta frequency, while global spike timing-dependent plasticity (STDP) protocols failed to induce LTP in these distal synapses. In contrast, IC synapses in apical and basal dendrites undergo plasticity with both NMDA-spikes and STDP protocols but to a smaller extent compared with LOT synapses. These results are consistent with a self-potentiating mechanism of odor information via NMDA-spikes that can form branch-specific memory traces of odors that can further associate with contextual IC information via STDP mechanisms to provide cognitive and emotional value to odors.
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Affiliation(s)
- Amit Kumar
- Department of Physiology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Edi Barkai
- Department of Neurobiology, University of Haifa, Haifa, Israel
| | - Jackie Schiller
- Department of Physiology, Technion-Israel Institute of Technology, Haifa, Israel
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3
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Bolding KA, Nagappan S, Han BX, Wang F, Franks KM. Recurrent circuitry is required to stabilize piriform cortex odor representations across brain states. eLife 2020; 9:e53125. [PMID: 32662420 PMCID: PMC7360366 DOI: 10.7554/elife.53125] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 06/19/2020] [Indexed: 11/13/2022] Open
Abstract
Pattern completion, or the ability to retrieve stable neural activity patterns from noisy or partial cues, is a fundamental feature of memory. Theoretical studies indicate that recurrently connected auto-associative or discrete attractor networks can perform this process. Although pattern completion and attractor dynamics have been observed in various recurrent neural circuits, the role recurrent circuitry plays in implementing these processes remains unclear. In recordings from head-fixed mice, we found that odor responses in olfactory bulb degrade under ketamine/xylazine anesthesia while responses immediately downstream, in piriform cortex, remain robust. Recurrent connections are required to stabilize cortical odor representations across states. Moreover, piriform odor representations exhibit attractor dynamics, both within and across trials, and these are also abolished when recurrent circuitry is eliminated. Here, we present converging evidence that recurrently-connected piriform populations stabilize sensory representations in response to degraded inputs, consistent with an auto-associative function for piriform cortex supported by recurrent circuitry.
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Affiliation(s)
- Kevin A Bolding
- Department of Neurobiology, Duke University Medical SchoolDurhamUnited States
| | | | - Bao-Xia Han
- Department of Neurobiology, Duke University Medical SchoolDurhamUnited States
| | - Fan Wang
- Department of Neurobiology, Duke University Medical SchoolDurhamUnited States
| | - Kevin M Franks
- Department of Neurobiology, Duke University Medical SchoolDurhamUnited States
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4
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Hasselmo ME, Alexander AS, Hoyland A, Robinson JC, Bezaire MJ, Chapman GW, Saudargiene A, Carstensen LC, Dannenberg H. The Unexplored Territory of Neural Models: Potential Guides for Exploring the Function of Metabotropic Neuromodulation. Neuroscience 2020; 456:143-158. [PMID: 32278058 DOI: 10.1016/j.neuroscience.2020.03.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 03/30/2020] [Accepted: 03/31/2020] [Indexed: 12/16/2022]
Abstract
The space of possible neural models is enormous and under-explored. Single cell computational neuroscience models account for a range of dynamical properties of membrane potential, but typically do not address network function. In contrast, most models focused on network function address the dimensions of excitatory weight matrices and firing thresholds without addressing the complexities of metabotropic receptor effects on intrinsic properties. There are many under-explored dimensions of neural parameter space, and the field needs a framework for representing what has been explored and what has not. Possible frameworks include maps of parameter spaces, or efforts to categorize the fundamental elements and molecules of neural circuit function. Here we review dimensions that are under-explored in network models that include the metabotropic modulation of synaptic plasticity and presynaptic inhibition, spike frequency adaptation due to calcium-dependent potassium currents, and afterdepolarization due to calcium-sensitive non-specific cation currents and hyperpolarization activated cation currents. Neuroscience research should more effectively explore possible functional models incorporating under-explored dimensions of neural function.
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Affiliation(s)
- Michael E Hasselmo
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States.
| | - Andrew S Alexander
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
| | - Alec Hoyland
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
| | - Jennifer C Robinson
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
| | - Marianne J Bezaire
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
| | - G William Chapman
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
| | - Ausra Saudargiene
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
| | - Lucas C Carstensen
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
| | - Holger Dannenberg
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Ave., Boston, MA 02215, United States
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5
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GABA B receptors: modulation of thalamocortical dynamics and synaptic plasticity. Neuroscience 2020; 456:131-142. [PMID: 32194227 DOI: 10.1016/j.neuroscience.2020.03.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 03/05/2020] [Accepted: 03/06/2020] [Indexed: 01/03/2023]
Abstract
GABAB-receptors (GABAB-Rs) are metabotropic, G protein-coupled receptors for the neurotransmitter GABA. Their activation induces slow inhibitory control of the neuronal excitability mediated by pre- and postsynaptic inhibition. Presynaptically GABAB-Rs reduce GABA and glutamate release inhibiting presynaptic Ca2+ channels in both inhibitory and excitatory synapses while postsynaptic GABAB-Rs induce robust slow hyperpolarization by the activation of K+ channels. GABAB-Rs are activated by non-synaptic or volume transmission, which requires high levels of GABA release, either by the simultaneous discharge of GABAergic interneurons or very intense discharges in the thalamus or by means of the activation of a neurogliaform interneurons in the cortex. The main receptor subunits GABAB1a, GABAB1b and GABAB2 are strongly expressed in neurons and glial cells throughout the central nervous system and GABAB-R activation is related to many neuronal processes such as the modulation of rhythmic activity in several brain regions. In the thalamus, GABAB-Rs modulate the generation of the main thalamic rhythm, spindle waves. In the cerebral cortex, GABAB-Rs also modulate the most prominent emergent oscillatory activity-slow oscillations-as well as faster oscillations like gamma frequency. Further, recent studies evaluating the complexity expressed by the cortical network, a parameter associated with consciousness levels, have found that GABAB-Rs enhance this complexity, while their blockade decreases it. This review summarizes the current results on how the activation of GABAB-Rs affects the interchange of information between brain areas by controlling rhythmicity as well as synaptic plasticity.
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6
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Witkowski ED, Gao Y, Gavsyuk AF, Maor I, DeWalt GJ, Eldred WD, Mizrahi A, Davison IG. Rapid Changes in Synaptic Strength After Mild Traumatic Brain Injury. Front Cell Neurosci 2019; 13:166. [PMID: 31105533 PMCID: PMC6498971 DOI: 10.3389/fncel.2019.00166] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 04/08/2019] [Indexed: 12/12/2022] Open
Abstract
Traumatic brain injury (TBI) affects millions of Americans annually, but effective treatments remain inadequate due to our poor understanding of how injury impacts neural function. Data are particularly limited for mild, closed-skull TBI, which forms the majority of human cases, and for acute injury phases, when trauma effects and compensatory responses appear highly dynamic. Here we use a mouse model of mild TBI to characterize injury-induced synaptic dysfunction, and examine its progression over the hours to days after trauma. Mild injury consistently caused both locomotor deficits and localized neuroinflammation in piriform and entorhinal cortices, along with reduced olfactory discrimination ability. Using whole-cell recordings to characterize synaptic input onto piriform pyramidal neurons, we found moderate effects on excitatory or inhibitory synaptic function at 48 h after TBI and robust increase in excitatory inputs in slices prepared 1 h after injury. Excitatory increases predominated over inhibitory effects, suggesting that loss of excitatory-inhibitory balance is a common feature of both mild and severe TBI. Our data indicate that mild injury drives rapidly evolving alterations in neural function in the hours following injury, highlighting the need to better characterize the interplay between the primary trauma responses and compensatory effects during this early time period.
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Affiliation(s)
| | - Yuan Gao
- Department of Biology, Boston University, Boston, MA, United States
| | | | - Ido Maor
- Department of Neurobiology, Edmond & Lily Safra Center for Brain Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Gloria J. DeWalt
- Department of Biology, Boston University, Boston, MA, United States
| | | | - Adi Mizrahi
- Department of Neurobiology, Edmond & Lily Safra Center for Brain Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Ian G. Davison
- Department of Biology, Boston University, Boston, MA, United States
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7
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Hasselmo ME, Stern CE. A network model of behavioural performance in a rule learning task. Philos Trans R Soc Lond B Biol Sci 2019; 373:rstb.2017.0275. [PMID: 29483357 DOI: 10.1098/rstb.2017.0275] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2017] [Indexed: 01/04/2023] Open
Abstract
Humans demonstrate differences in performance on cognitive rule learning tasks which could involve differences in properties of neural circuits. An example model is presented to show how gating of the spread of neural activity could underlie rule learning and the generalization of rules to previously unseen stimuli. This model uses the activity of gating units to regulate the pattern of connectivity between neurons responding to sensory input and subsequent gating units or output units. This model allows analysis of network parameters that could contribute to differences in cognitive rule learning. These network parameters include differences in the parameters of synaptic modification and presynaptic inhibition of synaptic transmission that could be regulated by neuromodulatory influences on neural circuits. Neuromodulatory receptors play an important role in cognitive function, as demonstrated by the fact that drugs that block cholinergic muscarinic receptors can cause cognitive impairments. In discussions of the links between neuromodulatory systems and biologically based traits, the issue of mechanisms through which these linkages are realized is often missing. This model demonstrates potential roles of neural circuit parameters regulated by acetylcholine in learning context-dependent rules, and demonstrates the potential contribution of variation in neural circuit properties and neuromodulatory function to individual differences in cognitive function.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.
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Affiliation(s)
- Michael E Hasselmo
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Avenue, Boston, MA 02215, USA
| | - Chantal E Stern
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, 610 Commonwealth Avenue, Boston, MA 02215, USA
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8
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Kumar A, Schiff O, Barkai E, Mel BW, Poleg-Polsky A, Schiller J. NMDA spikes mediate amplification of inputs in the rat piriform cortex. eLife 2018; 7:38446. [PMID: 30575520 PMCID: PMC6333441 DOI: 10.7554/elife.38446] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 12/20/2018] [Indexed: 11/13/2022] Open
Abstract
The piriform cortex (PCx) receives direct input from the olfactory bulb (OB) and is the brain's main station for odor recognition and memory. The transformation of the odor code from OB to PCx is profound: mitral and tufted cells in olfactory glomeruli respond to individual odorant molecules, whereas pyramidal neurons (PNs) in the PCx responds to multiple, apparently random combinations of activated glomeruli. How these 'discontinuous' receptive fields are formed from OB inputs remains unknown. Counter to the prevailing view that olfactory PNs sum their inputs passively, we show for the first time that NMDA spikes within individual dendrites can both amplify OB inputs and impose combination selectivity upon them, while their ability to compartmentalize voltage signals allows different dendrites to represent different odorant combinations. Thus, the 2-layer integrative behavior of olfactory PN dendrites provides a parsimonious account for the nonlinear remapping of the odor code from bulb to cortex.
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Affiliation(s)
- Amit Kumar
- Department of Physiology, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
| | - Oded Schiff
- Department of Physiology, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
| | - Edi Barkai
- Department of Neurobiology, University of Haifa, Haifa, Israel
| | - Bartlett W Mel
- Biomedical Engineering Department, University of Southern California, Los Angeles, United States
| | - Alon Poleg-Polsky
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, United States
| | - Jackie Schiller
- Department of Physiology, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
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9
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Gerrard LB, Tantirigama MLS, Bekkers JM. Pre- and Postsynaptic Activation of GABA B Receptors Modulates Principal Cell Excitation in the Piriform Cortex. Front Cell Neurosci 2018; 12:28. [PMID: 29459821 PMCID: PMC5807346 DOI: 10.3389/fncel.2018.00028] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 01/18/2018] [Indexed: 12/16/2022] Open
Abstract
The piriform cortex (PC), like other cortical regions, normally operates in a state of dynamic equilibrium between excitation and inhibition. Here we examined the roles played by pre- and postsynaptic GABAB receptors in maintaining this equilibrium in the PC. Using whole-cell recordings in brain slices from the anterior PC of mice, we found that synaptic activation of postsynaptic GABAB receptors hyperpolarized the two major classes of layer 2 principal neurons and reduced the intrinsic electrical excitability of these neurons. Presynaptic GABAB receptors are expressed on the terminals of associational (intracortical) glutamatergic axons in the PC. Heterosynaptic activation of these receptors reduced excitatory associational inputs onto principal cells. Presynaptic GABAB receptors are also expressed on the axons of GABAergic interneurons in the PC, and blockade of these autoreceptors enhanced inhibitory inputs onto principal cells. Hence, presynaptic GABAB autoreceptors produce disinhibition of principal cells. To study the functional consequences of GABAB activation in vivo, we used 2-photon calcium imaging to simultaneously monitor the activity of ~200 layer 2 neurons. Superfusion of the GABAB agonist baclofen reduced spontaneous random firing but also promoted synchronous epileptiform activity. These findings suggest that, while GABAB activation can dampen excitability by engaging pre- and postsynaptic GABAB heteroreceptors on glutamatergic neurons, it can also promote excitability by disinhibiting principal cells by activating presynaptic GABAB autoreceptors on interneurons. Thus, depending on the dynamic balance of hetero- and autoinhibition, GABAB receptors can function as variable modulators of circuit excitability in the PC.
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Affiliation(s)
- Leah B Gerrard
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Malinda L S Tantirigama
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - John M Bekkers
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
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10
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Development and Organization of the Evolutionarily Conserved Three-Layered Olfactory Cortex. eNeuro 2017; 4:eN-REV-0193-16. [PMID: 28144624 PMCID: PMC5272922 DOI: 10.1523/eneuro.0193-16.2016] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 11/11/2016] [Accepted: 12/08/2016] [Indexed: 01/31/2023] Open
Abstract
The olfactory cortex is part of the mammalian cerebral cortex together with the neocortex and the hippocampus. It receives direct input from the olfactory bulbs and participates in odor discrimination, association, and learning (Bekkers and Suzuki, 2013). It is thought to be an evolutionarily conserved paleocortex, which shares common characteristics with the three-layered general cortex of reptiles (Aboitiz et al., 2002). The olfactory cortex has been studied as a “simple model” to address sensory processing, though little is known about its precise cell origin, diversity, and identity. While the development and the cellular diversity of the six-layered neocortex are increasingly understood, the olfactory cortex remains poorly documented in these aspects. Here is a review of current knowledge of the development and organization of the olfactory cortex, keeping the analogy with those of the neocortex. The comparison of olfactory cortex and neocortex will allow the opening of evolutionary perspectives on cortical development.
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11
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Bao X, Raguet LL, Cole SM, Howard JD, Gottfried J. The role of piriform associative connections in odor categorization. eLife 2016; 5. [PMID: 27130519 PMCID: PMC4884078 DOI: 10.7554/elife.13732] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 04/27/2016] [Indexed: 11/24/2022] Open
Abstract
Distributed neural activity patterns are widely proposed to underlie object identification and categorization in the brain. In the olfactory domain, pattern-based representations of odor objects are encoded in piriform cortex. This region receives both afferent and associative inputs, though their relative contributions to odor perception are poorly understood. Here, we combined a placebo-controlled pharmacological fMRI paradigm with multivariate pattern analyses to test the role of associative connections in sustaining olfactory categorical representations. Administration of baclofen, a GABA(B) agonist known to attenuate piriform associative inputs, interfered with within-category pattern separation in piriform cortex, and the magnitude of this drug-induced change predicted perceptual alterations in fine-odor discrimination performance. Comparatively, baclofen reduced pattern separation between odor categories in orbitofrontal cortex, and impeded within-category generalization in hippocampus. Our findings suggest that odor categorization is a dynamic process concurrently engaging stimulus discrimination and generalization at different stages of olfactory information processing, and highlight the importance of associative networks in maintaining categorical boundaries. DOI:http://dx.doi.org/10.7554/eLife.13732.001 Imagine bringing your groceries home and tucking them into the refrigerator. You’ll probably organize the items by categories: lemons and oranges into the fruit drawer, carrots and cauliflower into the vegetable drawer. Categorization is essential, allowing us to interact with the world in the most efficient way possible. If the differences between objects are not relevant to the task at hand, the brain will group objects together based on their shared properties and develop mental representations of the “categories”. Importantly, we are still aware of the distinctions between objects within the same category. Categories of odor (for example, minty or fruity) are represented in a part of the brain called the olfactory (or piriform) cortex, which receives information from odor cues as well as “top-down” information from other areas of the brain. But how do these top-down pathways influence odor categorization? Bao et al. asked how the brain solves the problem of categorizing odors. For the experiments, human volunteers smelled six familiar odors belonging to three different categories while their brain activity was monitored using a magnetic resonance imaging (fMRI) scanner. Then, half of the participants were given a drug called baclofen that prevents top-down inputs, but not odor cues, from reaching the piriform cortex, while the rest received a placebo. After five days of taking the medication, all of the volunteers had another session of fMRI where they had to categorize the same odors as before. The experiments show that when comparing the fMRI scans before and after the drug treatment, the representations of odors belonging to the same category became more distinct in the piriform cortex in the placebo group. Put differently, as the volunteers were repeatedly exposed to odors of well-known categories, they became better at discriminating individual odors within the same category. However, these changes were disrupted in the group of volunteers that took baclofen. Bao et al.’s findings indicate that this “practice makes perfect” approach to recognizing odors relies on top-down inputs into the piriform cortex. In future work it will be important to study the roles of these inputs in learning new categories of odors, and to investigate whether the mechanisms identified here apply to other sensory information and to more abstract knowledge. DOI:http://dx.doi.org/10.7554/eLife.13732.002
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Affiliation(s)
- Xiaojun Bao
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | | | - Sydni M Cole
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - James D Howard
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Jay Gottfried
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, United States.,Department of Psychology, Northwestern University Weinberg College of Arts and Sciences, Evanston, United States
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12
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Devore S, Pender-Morris N, Dean O, Smith D, Linster C. Basal forebrain dynamics during nonassociative and associative olfactory learning. J Neurophysiol 2015; 115:423-33. [PMID: 26561601 DOI: 10.1152/jn.00572.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 11/10/2015] [Indexed: 12/28/2022] Open
Abstract
Cholinergic and GABAergic projections from the horizontal diagonal band (HDB) and medial preoptic area (MCPO) of the basal forebrain to the olfactory system are associated with odor discrimination and odor learning, as well as modulation of neural responses in olfactory structures. Whereas pharmacological and lesion studies give insights into the functional role of these modulatory inputs on a slow timescale, the response dynamics of neurons in the HDB/MCPO during olfactory behaviors have not been investigated. In this study we examined how these neurons respond during two olfactory behaviors: spontaneous investigation of odorants and odor-reward association learning. We observe rich heterogeneity in the response dynamics of individual HDB/MCPO neurons, with a substantial fraction of neurons exhibiting task-related modulation. HDB/MCPO neurons show both rapid and transient responses during bouts of odor investigation and slow, long-lasting modulation of overall response rate based on behavioral demands. Specifically, baseline rates were higher during the acquisition phase of an odor-reward association than during spontaneous investigation or the recall phase of an odor reward association. Our results suggest that modulatory projections from the HDB/MCPO are poised to influence olfactory processing on multiple timescales, from hundreds of milliseconds to minutes, and are therefore capable of rapidly setting olfactory network dynamics during odor processing and learning.
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Affiliation(s)
- Sasha Devore
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York; and
| | | | - Owen Dean
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York; and
| | - David Smith
- Department of Psychology, Cornell University, Ithaca, New York
| | - Christiane Linster
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York; and
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13
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Sheridan DC, Hughes AR, Erdélyi F, Szabó G, Hentges ST, Schoppa NE. Matching of feedback inhibition with excitation ensures fidelity of information flow in the anterior piriform cortex. Neuroscience 2014; 275:519-30. [PMID: 24969131 DOI: 10.1016/j.neuroscience.2014.06.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 05/24/2014] [Accepted: 06/12/2014] [Indexed: 11/18/2022]
Abstract
Odor-evoked responses in mitral cells of the olfactory bulb are characterized by prolonged patterns of action potential (spike) activity. If downstream neurons are to respond to each spike in these patterns, the duration of the excitatory response to one spike should be limited, enabling cells to respond to subsequent spikes. To test for such mechanisms, we performed patch-clamp recordings in slices of the mouse anterior piriform cortex. Mitral cell axons in the lateral olfactory tract (LOT) were stimulated electrically at different intensities and with various frequency patterns to mimic changing input conditions that the piriform cortex likely encounters in vivo. We found with cell-attached measurements that superficial pyramidal (SP) cells in layer 2 consistently responded to LOT stimulation across conditions with a limited number (1-2) of spikes per stimulus pulse. The key synaptic feature accounting for the limited spike number appeared to be somatic inhibition derived from layer 3 fast-spiking cells. This inhibition tracked the timing of the first spike in SP cells across conditions, which naturally limited the spike number to 1-2. These response features to LOT stimulation were, moreover, not unique to SP cells, also occurring in a population of fluorescently labeled interneurons in glutamic acid decarboxylase 65-eGFP mice. That these different cortical cells respond to incoming inputs with 1-2 spikes per stimulus may be especially critical for relaying bulbar information contained in synchronized oscillations at beta (15-30Hz) or gamma (30-80Hz) frequencies.
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Affiliation(s)
- D C Sheridan
- University of Colorado Anschutz Medical Campus, Department of Physiology & Biophysics, 12800 East 19th Avenue, Aurora, CO 80045, United States.
| | - A R Hughes
- Department of Biomedical Sciences, Colorado State University, 1680 Campus Delivery, Fort Collins, CO 80523, United States
| | - F Erdélyi
- Institute of Experimental Medicine, Division of Medical Gene Technology, Budapest, Hungary
| | - G Szabó
- Institute of Experimental Medicine, Division of Medical Gene Technology, Budapest, Hungary.
| | - S T Hentges
- Department of Biomedical Sciences, Colorado State University, 1680 Campus Delivery, Fort Collins, CO 80523, United States.
| | - N E Schoppa
- University of Colorado Anschutz Medical Campus, Department of Physiology & Biophysics, 12800 East 19th Avenue, Aurora, CO 80045, United States.
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14
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Kfir A, Ohad-Giwnewer N, Jammal L, Saar D, Golomb D, Barkai E. Learning-induced modulation of the GABAB-mediated inhibitory synaptic transmission: mechanisms and functional significance. J Neurophysiol 2014; 111:2029-38. [DOI: 10.1152/jn.00004.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Complex olfactory-discrimination (OD) learning results in a series of intrinsic and excitatory synaptic modifications in piriform cortex pyramidal neurons that enhance the circuit excitability. Such overexcitation must be balanced to prevent runway activity while maintaining the efficient ability to store memories. We showed previously that OD learning is accompanied by enhancement of the GABAA-mediated inhibition. Here we show that GABAB-mediated inhibition is also enhanced after learning and study the mechanism underlying such enhancement and explore its functional role. We show that presynaptic, GABAB-mediated synaptic inhibition is enhanced after learning. In contrast, the population-average postsynaptic GABAB-mediated synaptic inhibition is unchanged, but its standard deviation is enhanced. Learning-induced reduction in paired pulse facilitation in the glutamatergic synapses interconnecting pyramidal neurons was abolished by application of the GABAB antagonist CGP55845 but not by blocking G protein-gated inwardly rectifying potassium channels only, indicating enhanced suppression of excitatory synaptic release via presynaptic GABAB-receptor activation. In addition, the correlation between the strengths of the early (GABAA-mediated) and late (GABAB-mediated) synaptic inhibition was much stronger for each particular neuron after learning. Consequently, GABAB-mediated inhibition was also more efficient in controlling epileptic-like activity induced by blocking GABAA receptors. We suggest that complex OD learning is accompanied by enhancement of the GABAB-mediated inhibition that enables the cortical network to store memories, while preventing uncontrolled activity.
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Affiliation(s)
- Adi Kfir
- Departments of Neurobiology and Biology, Faculty of Sciences, University of Haifa, Haifa, Israel; and
| | - Naama Ohad-Giwnewer
- Departments of Neurobiology and Biology, Faculty of Sciences, University of Haifa, Haifa, Israel; and
| | - Luna Jammal
- Departments of Neurobiology and Biology, Faculty of Sciences, University of Haifa, Haifa, Israel; and
| | - Drorit Saar
- Departments of Neurobiology and Biology, Faculty of Sciences, University of Haifa, Haifa, Israel; and
| | - David Golomb
- Department of Physiology and Neurobiology, Faculty of Health Sciences, and the Zlotowski Center for Neuroscience, Ben-Gurion University, BeerSheva, Israel
| | - Edi Barkai
- Departments of Neurobiology and Biology, Faculty of Sciences, University of Haifa, Haifa, Israel; and
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15
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Barnes DC, Wilson DA. Sleep and olfactory cortical plasticity. Front Behav Neurosci 2014; 8:134. [PMID: 24795585 PMCID: PMC4001050 DOI: 10.3389/fnbeh.2014.00134] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 04/03/2014] [Indexed: 12/21/2022] Open
Abstract
In many systems, sleep plays a vital role in memory consolidation and synaptic homeostasis. These processes together help store information of biological significance and reset synaptic circuits to facilitate acquisition of information in the future. In this review, we describe recent evidence of sleep-dependent changes in olfactory system structure and function which contribute to odor memory and perception. During slow-wave sleep, the piriform cortex becomes hypo-responsive to odor stimulation and instead displays sharp-wave activity similar to that observed within the hippocampal formation. Furthermore, the functional connectivity between the piriform cortex and other cortical and limbic regions is enhanced during slow-wave sleep compared to waking. This combination of conditions may allow odor memory consolidation to occur during a state of reduced external interference and facilitate association of odor memories with stored hedonic and contextual cues. Evidence consistent with sleep-dependent odor replay within olfactory cortical circuits is presented. These data suggest that both the strength and precision of odor memories is sleep-dependent. The work further emphasizes the critical role of synaptic plasticity and memory in not only odor memory but also basic odor perception. The work also suggests a possible link between sleep disturbances that are frequently co-morbid with a wide range of pathologies including Alzheimer's disease, schizophrenia and depression and the known olfactory impairments associated with those disorders.
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Affiliation(s)
- Dylan C. Barnes
- Emotional Brain Institute, Nathan Kline Institute for Psychiatric ResearchOrangeburg, NY, USA
- Behavioral and Cognitive Neuroscience Program, City University of New YorkNew York, NY, USA
- Department of Biology, University of OklahomaNorman, OK, USA
| | - Donald A. Wilson
- Emotional Brain Institute, Nathan Kline Institute for Psychiatric ResearchOrangeburg, NY, USA
- Behavioral and Cognitive Neuroscience Program, City University of New YorkNew York, NY, USA
- Department of Biology, University of OklahomaNorman, OK, USA
- Department of Child and Adolescent Psychiatry, New York University Langone School of MedicineNew York, NY, USA
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16
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Neurons and circuits for odor processing in the piriform cortex. Trends Neurosci 2013; 36:429-38. [PMID: 23648377 DOI: 10.1016/j.tins.2013.04.005] [Citation(s) in RCA: 133] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 04/04/2013] [Accepted: 04/04/2013] [Indexed: 01/13/2023]
Abstract
Increased understanding of the early stages of olfaction has lead to a renewed interest in the higher brain regions responsible for forming unified 'odor images' from the chemical components detected by the nose. The piriform cortex, which is one of the first cortical destinations of olfactory information in mammals, is a primitive paleocortex that is critical for the synthetic perception of odors. Here we review recent work that examines the cellular neurophysiology of the piriform cortex. Exciting new findings have revealed how the neurons and circuits of the piriform cortex process odor information, demonstrating that, despite its superficial simplicity, the piriform cortex is a remarkably subtle and intricate neural circuit.
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17
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Chapuis J, Wilson DA. Cholinergic modulation of olfactory pattern separation. Neurosci Lett 2013; 545:50-3. [PMID: 23624024 DOI: 10.1016/j.neulet.2013.04.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 04/16/2013] [Indexed: 12/22/2022]
Abstract
Pattern separation plays an important role in perception and memory. In olfaction, pattern separation is critical component of piriform cortical odor processing contributing to behavioral perception of overlapping odor mixtures. Previous work has demonstrated that odor discrimination ability is modulated by acetylcholine. Here, we extended this previous work by using a distinct, well characterized complex odor stimulus set that has been shown to differentially involve pattern separation processes within piriform cortex. We find that the cholinergic muscarinic receptor agonist oxotremorine facilitates the acquisition of odor discrimination. Furthermore, the muscarinic receptor antagonist scopolamine impairs acquisition of odor discrimination even if the antagonist is limited to the piriform cortex. Finally, acetylcholine effects are most robust during discrimination acquisition, with minimal effects during expression.
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Affiliation(s)
- Julie Chapuis
- Child & Adolescent Psychiatry, New York University Langone School of Medicine, USA
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18
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Hagiwara A, Pal SK, Sato TF, Wienisch M, Murthy VN. Optophysiological analysis of associational circuits in the olfactory cortex. Front Neural Circuits 2012; 6:18. [PMID: 22529781 PMCID: PMC3329886 DOI: 10.3389/fncir.2012.00018] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 03/26/2012] [Indexed: 02/04/2023] Open
Abstract
Primary olfactory cortical areas receive direct input from the olfactory bulb, but also have extensive associational connections that have been mainly studied with classical anatomical methods. Here, we shed light on the functional properties of associational connections in the anterior and posterior piriform cortices (aPC and pPC) using optophysiological methods. We found that the aPC receives dense functional connections from the anterior olfactory nucleus (AON), a major hub in olfactory cortical circuits. The local recurrent connectivity within the aPC, long invoked in cortical autoassociative models, is sparse and weak. By contrast, the pPC receives negligible input from the AON, but has dense connections from the aPC as well as more local recurrent connections than the aPC. Finally, there are negligible functional connections from the pPC to aPC. Our study provides a circuit basis for a more sensory role for the aPC in odor processing and an associative role for the pPC.
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Affiliation(s)
- Akari Hagiwara
- Akari Hagiwara, Faculty of Medicine, Department of Biochemistry, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan. e-mail:
| | | | | | | | - Venkatesh N. Murthy
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, CambridgeMA, USA
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19
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Saar D, Reuveni I, Barkai E. Mechanisms underlying rule learning-induced enhancement of excitatory and inhibitory synaptic transmission. J Neurophysiol 2012; 107:1222-9. [DOI: 10.1152/jn.00356.2011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Training rats to perform rapidly and efficiently in an olfactory discrimination task results in robust enhancement of excitatory and inhibitory synaptic connectivity in the rat piriform cortex, which is maintained for days after training. To explore the mechanisms by which such synaptic enhancement occurs, we recorded spontaneous miniature excitatory and inhibitory synaptic events in identified piriform cortex neurons from odor-trained, pseudo-trained, and naive rats. We show that olfactory discrimination learning induces profound enhancement in the averaged amplitude of AMPA receptor-mediated miniature synaptic events in piriform cortex pyramidal neurons. Such physiological modifications are apparent at least 4 days after learning completion and outlast learning-induced modifications in the number of spines on these neurons. Also, the averaged amplitude of GABAA receptor-mediated miniature inhibitory synaptic events was significantly enhanced following odor discrimination training. For both excitatory and inhibitory transmission, an increase in miniature postsynaptic current amplitude was evident in most of the recorded neurons; however, some neurons showed an exceptionally great increase in the amplitude of miniature events. For both excitatory and inhibitory transmission, the frequency of spontaneous synaptic events was not modified after learning. These results suggest that olfactory discrimination learning-induced enhancement of synaptic transmission in cortical neurons is mediated by postsynaptic modulation of AMPA receptor-dependent currents and balanced by long-lasting modulation of postsynaptic GABAA receptor-mediated currents.
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Affiliation(s)
- Drorit Saar
- Department of Neurobiology, University of Haifa, Haifa, Israel
| | - Iris Reuveni
- Department of Neurobiology, University of Haifa, Haifa, Israel
| | - Edi Barkai
- Department of Neurobiology, University of Haifa, Haifa, Israel
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20
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Poo C, Isaacson JS. A major role for intracortical circuits in the strength and tuning of odor-evoked excitation in olfactory cortex. Neuron 2011; 72:41-8. [PMID: 21982367 DOI: 10.1016/j.neuron.2011.08.015] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2011] [Indexed: 11/18/2022]
Abstract
In primary sensory cortices, there are two main sources of excitation: afferent sensory input relayed from the periphery and recurrent intracortical input. Untangling the functional roles of these two excitatory pathways is fundamental for understanding how cortical neurons process sensory stimuli. Odor representations in the primary olfactory (piriform) cortex depend on excitatory sensory afferents from the olfactory bulb. However, piriform cortex pyramidal cells also receive dense intracortical excitatory connections, and the relative contribution of these two pathways to odor responses is unclear. Using a combination of in vivo whole-cell voltage-clamp recording and selective synaptic silencing, we show that the recruitment of intracortical input, rather than olfactory bulb input, largely determines the strength of odor-evoked excitatory synaptic transmission in rat piriform cortical neurons. Furthermore, we find that intracortical synapses dominate odor-evoked excitatory transmission in broadly tuned neurons, whereas bulbar synapses dominate excitatory synaptic responses in more narrowly tuned neurons.
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Affiliation(s)
- Cindy Poo
- Center for Neural Circuits and Behavior, Department of Neuroscience, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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21
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Abstract
The three-layered primary olfactory (piriform) cortex is the largest component of the olfactory cortex. Sensory and intracortical inputs converge on principal cells in the anterior piriform cortex (aPC). We characterize organization principles of the sensory and intracortical microcircuitry of layer II and III principal cells in acute slices of rat aPC using laser-scanning photostimulation and fast two-photon population Ca(2+) imaging. Layer II and III principal cells are set up on a superficial-to-deep vertical axis. We found that the position on this axis correlates with input resistance and bursting behavior. These parameters scale with distinct patterns of incorporation into sensory and associative microcircuits, resulting in a converse gradient of sensory and intracortical inputs. In layer II, sensory circuits dominate superficial cells, whereas incorporation in intracortical circuits increases with depth. Layer III pyramidal cells receive more intracortical inputs than layer II pyramidal cells, but with an asymmetric dorsal offset. This microcircuit organization results in a diverse hybrid feedforward/recurrent network of neurons integrating varying ratios of intracortical and sensory input depending on a cell's position on the superficial-to-deep vertical axis. Since burstiness of spiking correlates with both the cell's location on this axis and its incorporation in intracortical microcircuitry, the neuronal output mode may encode a given cell's involvement in sensory versus associative processing.
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22
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Abstract
The primary olfactory (or piriform) cortex is a trilaminar paleocortex that is thought to construct unified "odor images" from the odor components identified by the olfactory bulb. How the piriform cortex (PC) accomplishes this sophisticated synthetic task, despite its relatively simple architecture, is unknown. Here we used in vitro patch-clamp recordings from acute slices of the anterior PC of mice to identify microcircuits involved in excitatory synaptic processing. Cluster analysis confirmed the presence of two prominent classes of glutamatergic principal cells in the main input layer (layer II) of the PC: semilunar (SL) cells and superficial pyramidal (SP) cells. SL cells received stronger afferent excitatory input from the olfactory bulb, on average, than did SP cells. This was due to the larger mean strength of single-fiber afferents onto SL cells. In contrast, SP cells received stronger associational (intracortical) excitatory inputs, most likely due to their more extensive dendritic trees within the associational layers. Tissue-cut experiments and dual recordings from SL and SP cells in disinhibited slices were consistent with the distinctive patterns of connectivity of these two cell classes. Our findings suggest that the anterior PC employs at least two layers of excitatory synaptic processing: one involving strong afferent inputs onto SL cells, and another involving strong intracortical inputs onto SP cells. This architecture may allow the PC to sequentially process olfactory information within segregated subcircuits.
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23
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McGinley MJ, Westbrook GL. Membrane and synaptic properties of pyramidal neurons in the anterior olfactory nucleus. J Neurophysiol 2010; 105:1444-53. [PMID: 21123663 DOI: 10.1152/jn.00715.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The anterior olfactory nucleus (AON) is positioned to coordinate activity between the piriform cortex and olfactory bulbs, yet the physiology of AON principal neurons has been little explored. Here, we examined the membrane properties and excitatory synapses of AON principal neurons in brain slices of PND22-28 mice and compared their properties to principal cells in other olfactory cortical areas. AON principal neurons had firing rates, spike rate adaptation, spike widths, and I-V relationships that were generally similar to pyramidal neurons in piriform cortex, and typical of cerebral cortex, consistent with a role for AON in cortical processing. Principal neurons in AON had more hyperpolarized action potential thresholds, smaller afterhyperpolarizations, and tended to fire doublets of action potentials on depolarization compared with ventral anterior piriform cortex and the adjacent epileptogenic region preendopiriform nucleus (pEN). Thus, AON pyramidal neurons have enhanced membrane excitability compared with surrounding subregions. Interestingly, principal neurons in pEN were the least excitable, as measured by a larger input conductance, lower firing rates, and more inward rectification. Afferent and recurrent excitatory synapses onto AON pyramidal neurons had small amplitudes, paired pulse facilitation at afferent synapses, and GABA(B) modulation at recurrent synapses, a pattern similar to piriform cortex. The enhanced membrane excitability and recurrent synaptic excitation within the AON, together with its widespread outputs, suggest that the AON can boost and distribute activity in feedforward and feedback circuits throughout the olfactory system.
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Affiliation(s)
- Matthew J McGinley
- Vollum Institute, Oregon Health and Science University, Portland, Oregon, USA.
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24
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Hadley JK, Halliwell JV. Serotonin modulates glutamatergic transmission in the rat olfactory tubercle. Eur J Neurosci 2010; 31:659-72. [PMID: 20141530 DOI: 10.1111/j.1460-9568.2010.07084.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The olfactory tubercle (OT) is found in the brains of mammals that are highly dependent on their sense of smell. Its human analogue is the poorly understood anterior perforated substance. Previous work on rat brain slices identified two types of field potential responses from the OT. The association fibre (AF) pathway was sensitive to muscarinic modulation, whereas the lateral olfactory tract (LOT) fibre pathway was not. Here, we establish that serotonin (5-hydroxytryptamine; 5-HT) also inhibits field potential excitatory postsynaptic potentials (EPSPs) in the AF, but not in the LOT fibre, pathway. Parallel experiments with adenosine (ADO) excluded ADO mediation of the 5-HT effect. Exogenous 5-HT at 30 microm caused a long-lasting approximately 40% reduction in the amplitude of AF postsynaptic responses, without affecting the time-course of EPSP decline, indicating a fairly restricted disposition of the 5-HT receptors responsible. The 5-HT(1)-preferring, 5-HT(5)-preferring and 5-HT(7)-preferring agonist 5-carboxamidotryptamine caused similar inhibition at approximately 100 nm. The 5-HT(1A)-preferring ligand 8-hydroxy-di-n-propylamino-tetralin at 10 microm, and the 5-HT uptake inhibitor citalopram at 3 microm, caused inhibition of AF-stimulated field potential responses in the 5-10% range. Order-of-potency information suggested a receptor of the 5-HT(1B) or 5-HT(1D) subtype. The 5-HT(1D) agonist L-694,247 (1 microm) suppressed the AF response by approximately 10% when used on its own. After washing out of L-694,427, inhibition by 30 microm 5-HT was reduced to negligible levels. Allowing for a partial agonist action of L-694,427 and complex interactions of 5-HT receptors within the OT, these results support the presence of active 5-HT(1D)-type receptors in the principal cell layer of the OT.
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Affiliation(s)
- J K Hadley
- Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E6BT, UK
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25
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Dendritic compartment and neuronal output mode determine pathway-specific long-term potentiation in the piriform cortex. J Neurosci 2009; 29:13649-61. [PMID: 19864577 DOI: 10.1523/jneurosci.2672-09.2009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The apical dendrite of layer 2/3 pyramidal cells in the piriform cortex receives two spatially distinct inputs: one projecting onto the distal apical dendrite in sensory layer 1a, the other targeting the proximal apical dendrite in layer 1b. We observe an expression gradient of A-type K(+) channels that weakens the backpropagating action potential-mediated depolarization in layer 1a compared with layer 1b. We find that the pairing of presynaptic and postsynaptic firing leads to significantly smaller Ca(2+) signals in the distal dendritic spines in layer 1a compared with the proximal spines in layer 1b. The consequence is a selective failure to induce long-term potentiation (LTP) in layer 1a, which can be rescued by pharmacological enhancement of action potential backpropagation. In contrast, LTP induction by pairing presynaptic and postsynaptic firing is possible in layer 1b but requires bursting of the postsynaptic cell. This output mode strongly depends on the balance of excitation and inhibition in the piriform cortex. We show, on the single-spine level, how the plasticity of functionally distinct synapses is gated by the intrinsic electrical properties of piriform cortex layer 2 pyramidal cell dendrites and the cellular output mode.
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26
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Sizemore M, Perkel DJ. Noradrenergic and GABA B receptor activation differentially modulate inputs to the premotor nucleus RA in zebra finches. J Neurophysiol 2008; 100:8-18. [PMID: 18463188 DOI: 10.1152/jn.01212.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Neuromodulators can rapidly modify neural circuits, altering behavior. Songbirds provide an excellent system for studying the role of neuromodulation in modifying circuits that underlie behavior because song learning and production are mediated by a discrete set of interconnected nuclei. We examined the neuromodulatory effects of noradrenergic and GABA B receptor activation on synaptic inputs to the premotor robust nucleus of the arcopallium (RA) in zebra finches using whole cell voltage-clamp recording in vitro. In adults, norepinephrine strongly reduced input from the lateral magnocellular nucleus of the anterior nidopallium (LMAN) but only slightly reduced the input from nucleus HVC (proper name), the excitatory input from axon collaterals of other RA neurons, and input from GABAergic interneurons. The effect of norepinephrine was mimicked by the alpha2 adrenoceptor agonist UK14,304 and blocked by the alpha2 antagonist yohimbine. Conversely, the GABA B receptor agonist baclofen strongly decreased HVC, collateral, and GABAergic inputs to RA neurons while causing little reduction in the LMAN input. In juveniles undergoing song learning, norepinephrine reduced the LMAN input, caused only a small reduction in the HVC input, and greatly reduced the collateral and GABAergic inputs. Baclofen caused similar results in juvenile and adult birds, reducing HVC, collateral, and GABAergic inputs significantly more than the LMAN input. Significant increases in paired-pulse ratio accompanied all reductions in synaptic transmission, suggesting a presynaptic locus. The reduction in the LMAN input by norepinephrine may be important for mediating changes in song elicited by different social contexts and is well-placed to play a role in song learning.
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Affiliation(s)
- Max Sizemore
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, Washington, USA.
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27
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Yang SC, Chiu TH, Yang HW, Min MY. Presynaptic adenosine A1 receptors modulate excitatory synaptic transmission in the posterior piriform cortex in rats. Brain Res 2007; 1156:67-79. [PMID: 17512911 DOI: 10.1016/j.brainres.2007.04.049] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Revised: 04/16/2007] [Accepted: 04/19/2007] [Indexed: 11/25/2022]
Abstract
The effect of adenosine on the fEPSP was examined in the lateral olfactory tract (Ia input) and associative tract (Ib input) of the rat piriform cortex. The fEPSP evoked in the Ia input showed paired-pulse facilitation, while that in the Ib input showed paired-pulse depression, suggesting a lower resting release probability in the Ia input. This was supported by results showing that MK801 blocked the NMDA receptor-induced fEPSP more rapidly in the Ib input than the Ia input. Adenosine caused dose-dependent inhibition of the fEPSP in both inputs, the sensitivity being higher in the Ib input. This effect was mimicked by the A(1) receptor agonist, CHA, and antagonized by co-application of the A(1) receptor antagonist, DPCPX, showing that adenosine was acting at A(1) receptors. Application of DPCPX alone caused an increase in the fEPSP, the increase being larger in the Ia input. DPCPX also caused paired-pulse depression in both inputs, and the paired-pulse ratio measured in its presence was very similar in both inputs. These results suggest there is a lower endogenous concentration of adenosine in the Ib sublayer than the Ia sublayer, which might account for the native difference in the resting release probability of the two inputs. The adenosine-induced inhibition of the fEPSP in both inputs was associated with a significant reduction in the rate at which MK801 blocked NMDA receptor-mediated fEPSP activity, suggesting a presynaptic location of the A(1) receptors. Blocking of N-, P/Q-type calcium channels occluded the inhibition by adenosine, indicating that they are downstream effectors of presynaptic A(1) receptor activation.
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Affiliation(s)
- Su-Ching Yang
- Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 101, Taiwan
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28
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Lei H, Mooney R, Katz LC. Synaptic integration of olfactory information in mouse anterior olfactory nucleus. J Neurosci 2006; 26:12023-32. [PMID: 17108176 PMCID: PMC6674854 DOI: 10.1523/jneurosci.2598-06.2006] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Individual odorants activate only a small fraction of mitral cells in the mouse main olfactory bulb (MOB). Odor mixtures are represented by a combination of activated mitral cells, forming reproducible activation maps in the olfactory bulb. However, how the activation of a cohort of narrowly tuned mitral cells by odor mixtures is read out synaptically by neurons in higher-level olfactory structures, such as the anterior olfactory nucleus (AON), is mostly unknown. In the current study, we used intracellular and extracellular recordings to examine and compare responses of AON neurons and MOB mitral cells to a panel of structurally diverse odorants presented either as mixtures or as individual components. We found that a majority of individual AON neurons could be synaptically activated by several mixtures of structurally dissimilar components and by several dissimilar components in an effective mixture. The suprathreshold response of an AON neuron to an effective mixture often exceeded the sum of its suprathreshold responses to all of the components in that mixture, indicating a nonlinear combinatorial interaction. In contrast to the broad responsiveness of AON neurons, the majority of mitral cells were activated by only one or two components in a single mixture. The broader responsiveness of AON neurons relative to mitral cells suggests that individual AON neurons synaptically integrate several functionally distinct mitral cell inputs.
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Affiliation(s)
- Huimeng Lei
- Howard Hughes Medical Institute and
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710
| | - Richard Mooney
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710
| | - Lawrence C. Katz
- Howard Hughes Medical Institute and
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710
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29
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Wilson DA, Kadohisa M, Fletcher ML. Cortical contributions to olfaction: Plasticity and perception. Semin Cell Dev Biol 2006; 17:462-70. [PMID: 16750923 DOI: 10.1016/j.semcdb.2006.04.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In most sensory systems, the sensory cortex is the place where sensation approaches perception. As described in this review, olfaction is no different. The olfactory system includes both primary and higher order cortical regions. These cortical structures perform computations that take highly analytical afferent input and synthesize it into configural odor objects. Cortical plasticity plays an important role in this synthesis and may underlie olfactory perceptual learning. Olfactory cortex is also involved in odor memory and association of odors with multimodal input and contexts. Finally, the olfactory cortex serves as an important sensory gate, modulating information throughput based on recent experience and behavioral state.
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Affiliation(s)
- Donald A Wilson
- Department of Zoology, University of Oklahoma, Norman, OK 73019, USA.
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30
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Franks KM, Isaacson JS. Synapse-Specific Downregulation of NMDA Receptors by Early Experience: A Critical Period for Plasticity of Sensory Input to Olfactory Cortex. Neuron 2005; 47:101-14. [PMID: 15996551 DOI: 10.1016/j.neuron.2005.05.024] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2004] [Revised: 04/21/2004] [Accepted: 05/17/2005] [Indexed: 10/25/2022]
Abstract
Olfaction is required at birth for survival; however, little is known about the maturation of olfactory cortical circuits. Here we show that in vivo sensory experience mediates the development of excitatory transmission in pyramidal neurons of rat olfactory cortex. We find a postnatal critical period during which there is an experience-dependent increase in the contribution of AMPARs versus NMDARs to transmission at primary sensory synapses but not associational inputs. The shift in receptors underlying transmission is mediated by a strong activity-dependent downregulation of NMDARs and modest increase in AMPARs. Sensory activity leads to a loss of "silent" NMDAR-only synapses and an increase in threshold for inducing long-term plasticity. These results indicate the importance of early olfactory experience in the establishment of cortical circuits and could reflect mechanisms governing early olfactory "imprinting."
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Affiliation(s)
- Kevin M Franks
- Department of Neuroscience, University of California, San Diego School of Medicine, La Jolla, CA 92093, USA
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31
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Porter JT, Nieves D. Presynaptic GABAB receptors modulate thalamic excitation of inhibitory and excitatory neurons in the mouse barrel cortex. J Neurophysiol 2004; 92:2762-70. [PMID: 15254073 PMCID: PMC3677950 DOI: 10.1152/jn.00196.2004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cortical inhibition plays an important role in the processing of sensory information, and the enlargement of receptive fields by the in vivo application of GABAB receptor antagonists indicates that GABAB receptors mediate some of this cortical inhibition. Although there is evidence of postsynaptic GABAB receptors on cortical neurons, there is no evidence of GABAB receptors on thalamocortical terminals. Therefore to determine if presynaptic GABAB receptors modulate the thalamic excitation of layer IV inhibitory neurons and excitatory neurons in layers II-III and IV of the somatosensory "barrel" cortex of mice, we used a thalamocortical slice preparation and patch-clamp electrophysiology. Stimulation of the ventrobasal thalamus elicited excitatory postsynaptic currents (EPSCs) in cortical neurons. Bath application of baclofen, a selective GABAB receptor agonist, reversibly decreased AMPA receptor-mediated and N-methyl-D-aspartate (NMDA) receptor-mediated EPSCs in inhibitory and excitatory neurons. The GABAB receptor antagonist, CGP 35348, reversed the inhibition produced by baclofen. Blocking the postsynaptic GABAB receptor-mediated effects with a Cs+ -based recording solution did not affect the inhibition, suggesting a presynaptic effect of baclofen. Baclofen reversibly increased the paired-pulse ratio and the coefficient of variation, consistent with the presynaptic inhibition of glutamate release. Our results indicate that the presynaptic activation of GABAB receptors modulates thalamocortical excitation of inhibitory and excitatory neurons and provide another mechanism by which cortical inhibition can modulate the processing of sensory information.
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Affiliation(s)
- James T Porter
- Department of Pharmacology and Toxicology, Ponce School of Medicine, Ponce, Puerto Rico, 00732.
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Hasselmo ME, Fehlau BP. Differences in time course of ACh and GABA modulation of excitatory synaptic potentials in slices of rat hippocampus. J Neurophysiol 2001; 86:1792-802. [PMID: 11600640 DOI: 10.1152/jn.2001.86.4.1792] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of muscarinic receptors and GABA(B) receptors causes presynaptic inhibition of glutamatergic synaptic potentials at excitatory feedback connections in cortical structures. These effects may regulate dynamics in cortical structures, with presynaptic inhibition allowing extrinsic afferent input to dominate during encoding, while the absence of presynaptic inhibition allows stronger excitatory feedback during retrieval or consolidation. However, proposals for a functional role of such modulatory effects strongly depend on the time course of these modulatory effects; how rapidly can they turn off and on? In brain slice preparations of hippocampal region CA1, we have explored the time course of suppression of extracellularly recorded synaptic potentials after pressure pulse application of acetylcholine and GABA. Acetylcholine causes suppression of extracellular potentials with onset time constants between 1 and 2 s, and decay constants ranging between 10 and 20 s, even with very brief injection pulses. GABA causes suppression of extracellular potentials with onset time constants between 0.2 and 0.7 s, and decay time constants that decrease to values shorter than 2 s for very brief injection pulses. These techniques do not give an exact measure of the physiological time course in vivo, but they give a notion of the relative time course of the two modulators. The slow changes due to activation of muscarinic acetylcholine receptors may alter the dynamics of cortical circuits over longer intervals (e.g., between different stages of waking and sleep), setting dynamics appropriate for encoding versus consolidation processes. The faster changes in synaptic potentials caused by GABA could cause changes within each cycle of the theta rhythm, rapidly switching between encoding and retrieval dynamics during exploration.
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Affiliation(s)
- M E Hasselmo
- Department of Psychology, Program in Neuroscience and Center for BioDynamics, Boston University, Boston, Massachusetts 02215, USA.
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De Rosa E, Hasselmo ME, Baxter MG. Contribution of the cholinergic basal forebrain to proactive interference from stored odor memories during associative learning in rats. Behav Neurosci 2001. [DOI: 10.1037/0735-7044.115.2.314] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Stojic AS, Lane RD, Killackey HP, Rhoades RW. Suppression of hindlimb inputs to S-I forelimb-stump representation of rats with neonatal forelimb removal: GABA receptor blockade and single-cell responses. J Neurophysiol 2000; 83:3377-87. [PMID: 10848556 DOI: 10.1152/jn.2000.83.6.3377] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neonatal forelimb removal in rats results in the development of inappropriate hindlimb inputs in the forelimb-stump representation of primary somatosensory cortex (S-I) that are revealed when GABA(A) and GABA(B) receptor activity are blocked. Experiments carried out to date have not made clear what information is being suppressed at the level of individual neurons. In this study, three potential ways in which GABA-mediated inhibition could suppress hindlimb expression in the S-I stump representation were evaluated: silencing S-I neurons with dual stump and hindlimb receptive fields, silencing neurons with receptive fields restricted to the hindlimb alone, and/or selective silencing of hindlimb inputs to neurons that normally express a stump receptive field only. These possibilities were tested using single-unit recording techniques to evaluate the receptive fields of S-I forelimb-stump neurons before, during, and after blockade of GABA receptors with bicuculline methiodide (for GABA(A)) and saclofen (for GABA(B)). Recordings were also made from normal rats for comparison. Of 92 neurons recorded from the S-I stump representation of neonatally amputated rats, only 2.2% had receptive fields that included the hindlimb prior to GABA receptor blockade. During GABA receptor blockade, 54.3% of these cells became responsive to the hindlimb, and in all but two cases, these same neurons also expressed a stump receptive field. Most of these cells (82.0%) expressed only stump receptive fields prior to GABA receptor blockade. In 71 neurons recorded from normal rats, only 5 became responsive to the hindlimb during GABA receptor blockade. GABA receptor blockade of cortical neurons, in both normal and neonatally amputated rats, resulted in significant enlargements of receptive fields as well as the emergence of receptive fields for neurons that were normally unresponsive. GABA receptor blockade also resulted in increases in both the spontaneous activity and response magnitudes of these neurons. These data support the conclusion that GABA mechanisms generally act to specifically suppress hindlimb inputs to S-I forelimb-stump neurons that normally express a receptive field on the forelimb stump only.
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Affiliation(s)
- A S Stojic
- Department of Anatomy and Neurobiology, Medical College of Ohio, Toledo, Ohio 43699, USA
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Wang X, Lambert NA. GABA(B) receptors couple to potassium and calcium channels on identified lateral perforant pathway projection neurons. J Neurophysiol 2000; 83:1073-8. [PMID: 10669518 DOI: 10.1152/jn.2000.83.2.1073] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of presynaptic GABA(B) receptors inhibits neurotransmitter release at most cortical synapses, at least in part because of inhibition of voltage-gated calcium channels. One synapse where this is not the case is the lateral perforant pathway synapse onto dentate granule cells in the hippocampus. The current study was conducted to determine whether the neurons that make these synapses express GABA(B) receptors that can couple to ion channels. Perforant pathway projection neurons were labeled by injecting retrograde tracer into the dorsal hippocampus. The GABA(B) receptor agonist baclofen (10 microM) activated inwardly rectifying potassium channels and inhibited currents mediated by voltage-gated calcium channels in retrogradely labeled neurons in layer II of the lateral entorhinal cortex. These effects were reversed by coapplication of the selective GABA(B) receptor antagonist CGP 55845A (1 microM). Equivalent effects were produced by 100 microM adenosine, which inhibits neurotransmitter release at lateral perforant pathway synapses. The effects of baclofen and adenosine on inward currents were largely occlusive. These results suggest that the absence of GABA(B) receptor-mediated presynaptic inhibition at lateral perforant pathway synapses is not simply due to a failure to express these receptors and imply that GABA(B) receptors can either be selectively localized or regulated at terminal versus somatodendritic domains.
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Affiliation(s)
- X Wang
- Department of Pharmacology and Toxicology, Medical College of Georgia, and Medical Research Service, Veterans Administration Medical Center, Augusta, Georgia 30912-2300, USA
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36
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Abstract
Studies of the function of the basal forebrain have focused on cholinergic neurons that project to cortical and limbic structures critical for various cognitive abilities. Recent experiments suggest that these neurons serve a modulatory function in cognition, by optimizing cortical information processing and influencing attention.
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Affiliation(s)
- M G Baxter
- Department of Psychology, Harvard University, 984 William James Hall, 33 Kirkland Street, Cambridge, Massachusetts 02138, USA.
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Modeling the Piriform Cortex. Cereb Cortex 1999. [DOI: 10.1007/978-1-4615-4903-1_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Hasselmo ME, Wyble BP, Wallenstein GV. Encoding and retrieval of episodic memories: Role of cholinergic and GABAergic modulation in the hippocampus. Hippocampus 1998. [DOI: 10.1002/(sici)1098-1063(1996)6:6%3c693::aid-hipo12%3e3.0.co;2-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Abstract
Computational modeling of neural substrates provides an excellent theoretical framework for the understanding of the computational roles of neuromodulation. In this review, we illustrate, with a large number of modeling studies, the specific computations performed by neuromodulation in the context of various neural models of invertebrate and vertebrate preparations. We base our characterization of neuromodulations on their computational and functional roles rather than on anatomical or chemical criteria. We review the main framework in which neuromodulation has been studied theoretically (central pattern generation and oscillations, sensory processing, memory and information integration). Finally, we present a detailed mathematical overview of how neuromodulation has been implemented at the single cell and network levels in modeling studies. Overall, neuromodulation is found to increase and control computational complexity.
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Affiliation(s)
- J M Fellous
- Brandeis University, Volen Center for Complex Systems, Waltham, MA 02254-9110, USA
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Sohal VS, Hasselmo ME. Changes in GABAB modulation during a theta cycle may be analogous to the fall of temperature during annealing. Neural Comput 1998; 10:869-82. [PMID: 9573410 DOI: 10.1162/089976698300017539] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Changes in GABA modulation may underlie experimentally observed changes in the strength of synaptic transmission at different phases of the theta rhythm (Wyble, Linster, & Hasselmo, 1997). Analysis demonstrates that these changes improve sequence disambiguation by a neural network model of CA3. We show that in the framework of Hopfield and Tank (1985), changes in GABA suppression correspond to changes in the effective temperature and the relative energy of data terms and constraints of an analog network. These results suggest that phasic changes in the activity of inhibitory interneurons during a theta cycle may produce dynamics that resemble annealing. These dynamics may underlie a role for the theta cycle in improving sequence retrieval for spatial navigation.
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Affiliation(s)
- V S Sohal
- Department of Psychology, Harvard University, Cambridge, MA 02138, USA
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41
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Abstract
Computational models of hippocampal region CA3 were used to study the role of theta rhythm in storage and retrieval of temporal sequences of neuronal activity patterns. Retrieval of multiple overlapping temporal sequences requires a mechanism for disambiguation, e.g., for choosing between two sequences with the same starting pattern but different final patterns (forked sequences). Modulatory input to the hippocampus from the medial septum may enhance the disambiguation of pattern sequences by causing phasic changes in the relative strength of afferent input and recurrent excitation. In the models, the strength of recurrent synaptic transmission is modulated by activation of GABA(B) receptors. Theta frequency inputs from the medial septum cause oscillations in the levels of GABA in the model, producing phasic changes in the strength of synaptic potentials during a theta cycle similar to those observed experimentally (Wyble et al., Soc Neurosci Abstr 1997;23: 197.7). These phasic changes in GABA(B) suppression improve sequence disambiguation in the simulations, as previously shown with analysis of a simpler model (Sohal and Hasselmo, Neural Comp 1998;10:889-902). In addition, tonic changes in levels of cholinergic modulation enhance the storage of forked sequences by preventing a strong influence of recurrent synapses during storage.
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Affiliation(s)
- V S Sohal
- Department of Psychology, Harvard University, Cambridge, Massachusetts 02138, USA
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Gil Z, Connors BW, Amitai Y. Differential regulation of neocortical synapses by neuromodulators and activity. Neuron 1997; 19:679-86. [PMID: 9331357 DOI: 10.1016/s0896-6273(00)80380-3] [Citation(s) in RCA: 428] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Synapses are continually regulated by chemical modulators and by their own activity. We tested the specificity of regulation in two excitatory pathways of the neocortex: thalamocortical (TC) synapses, which mediate specific inputs, and intracortical (IC) synapses, which mediate the recombination of cortical information. Frequency-sensitive depression was much stronger in TC synapses than in IC synapses. The two synapse types were differentially sensitive to presynaptic neuromodulators: only IC synapses were suppressed by activation of GABA(B) receptors, only TC synapses were enhanced by nicotinic acetylcholine receptors, and muscarinic acetylcholine receptors suppressed both synapse types. Modulators also differentially altered the frequency sensitivity of the synapses. Our results suggest a mechanism by which the relative strength and dynamics of input and associational pathways of neocortex are regulated during changes in behavioral state.
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Affiliation(s)
- Z Gil
- Department of Physiology, Zlotowski Center for Neuroscience, Ben-Gurion University, Beer-Sheva, Israel
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Wallenstein GV, Hasselmo ME. GABAergic modulation of hippocampal population activity: sequence learning, place field development, and the phase precession effect. J Neurophysiol 1997; 78:393-408. [PMID: 9242288 DOI: 10.1152/jn.1997.78.1.393] [Citation(s) in RCA: 229] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A detailed biophysical model of hippocampal region CA3 was constructed to study how GABAergic modulation influences place field development and the learning and recall of sequence information. Simulations included 1,000 multicompartmental pyramidal cells, each consisting of seven intrinsic and four synaptic currents, and 200 multicompartmental interneurons, consisting of two intrinsic and four synaptic currents. Excitatory rhythmic septal input to the apical dendrites of pyramidal cells and both excitatory and inhibitory input to interneurons at theta frequencies provided a cellular basis for the development of theta and gamma frequency oscillations in population activity. The fundamental frequency of theta oscillations was dictated by the driving rhythm from the septum. Gamma oscillation frequency, however, was determined by both the decay time of the gamma-aminobutyric acid-A (GABA(A))-receptor-mediated synaptic current and the overall level of excitability in interneurons due to alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid and N-methyl-D-aspartate (NMDA)-receptor-gated channel activation. During theta population activity, total GABA(B)-receptor-mediated conductance levels were found to gradually rise and fall in rhythmic fashion with the predominant population frequency (theta rhythm). This resulted in periodic GABA(B)-receptor-mediated suppression of excitatory synaptic transmission at recurrent collaterals (intrinsic fibers) of pyramidal cells and suppression of inhibitory synaptic transmission to both pyramidal cells and interneurons. To test the ability of the model to learn and recall temporal sequence information, a completion task was employed. During learning, the network was presented a sequence of nonorthogonal spatial patterns. Each input pattern represented a spatial "location" of a simulated rat running a specific navigational path. Hebbian-type learning was expressed as an increase in postsynaptic NMDA-receptor-mediated conductances. Because of several factors including the sparse, asymmetric excitatory synaptic connections among pyramidal cells in the model and a sufficient degree of random "background" firing unrelated to the input patterns, repeated simulated runs resulted in the gradual emergence of place fields where a given cell began to respond to a contiguous segment of locations on the path. During recall, the simulated rat was placed at a random location on the previously learned path and tested to see whether the sequence of locations could be completed on the basis of this initial position. Periodic GABA(B)-receptor-mediated suppression of excitatory and inhibitory transmission at intrinsic but not afferent fibers resulted in sensory information about location being dominant during early portions of each theta cycle when GABA(B)-receptor-related effects were highest. This suppression declined with levels of GABA(B) receptor activation toward the end of a theta cycle, resulting in an increase in synaptic transmission at intrinsic fibers and the subsequent recall of a segment of the entire location sequence. This scenario typically continued across theta cycles until the full sequence was recalled. When the GABA(B)-receptor-mediated suppression of excitatory and inhibitory transmission at intrinsic fibers was not included in the model, place field development was curtailed and the network consequently exhibited poor learning and recall performance. This was, in part, due to increased competition of information from intrinsic and afferent fibers during early portions of each theta cycle. Because afferent sensory information did not dominate early in each cycle, the current location of the rat was obscured by ongoing activity from intrinsic sources. (ABSTRACT TRUNCATED)
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Affiliation(s)
- G V Wallenstein
- Department of Psychology and Program in Neuroscience, Harvard University, Cambridge, Massachusetts 02138, USA
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44
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Hasselmo ME, Linster C, Patil M, Ma D, Cekic M. Noradrenergic suppression of synaptic transmission may influence cortical signal-to-noise ratio. J Neurophysiol 1997; 77:3326-39. [PMID: 9212278 DOI: 10.1152/jn.1997.77.6.3326] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Norepinephrine has been proposed to influence signal-to-noise ratio within cortical structures, but the exact cellular mechanisms underlying this influence have not been described in detail. Here we present data on a cellular effect of norepinephrine that could contribute to the influence on signal-to-noise ratio. In brain slice preparations of the rat piriform (olfactory) cortex, perfusion of norepinephrine causes a dose-dependent suppression of excitatory synaptic potentials in the layer containing synapses among pyramidal cells in the cortex (layer Ib), while having a weaker effect on synaptic potentials in the afferent fiber layer (layer Ia). Effects of norepinephrine were similar in dose-response characteristics and laminar selectivity to the effects of the cholinergic agonist carbachol, and combined perfusion of both agonists caused effects similar to an equivalent concentration of a single agonist. In a computational model of the piriform cortex, we have analyzed the effect of noradrenergic suppression of synaptic transmission on signal-to-noise ratio. The selective suppression of excitatory intrinsic connectivity decreases the background activity of modeled neurons relative to the activity of neurons receiving direct afferent input. This can be interpreted as an increase in signal-to-noise ratio, but the term noise does not accurately characterize activity dependent on the intrinsic spread of excitation, which would more accurately be described as interpretation or retrieval. Increases in levels of norepinephrine mediated by locus coeruleus activity appear to enhance the influence of extrinsic input on cortical representations, allowing a pulse of norepinephrine in an arousing context to mediate formation of memories with a strong influence of environmental variables.
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Affiliation(s)
- M E Hasselmo
- Department of Psychology and Program in Neuroscience, Harvard University, Cambridge, Massachusetts 02138, USA
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Hasselmo ME, Cekic M. Suppression of synaptic transmission may allow combination of associative feedback and self-organizing feedforward connections in the neocortex. Behav Brain Res 1996; 79:153-61. [PMID: 8883827 DOI: 10.1016/0166-4328(96)00010-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Selective suppression of synaptic transmission during learning is proposed as a physiological mechanism for combining associative memory function at feedback synapses with self-organization of feedforward synapses in neocortical structures. A computational model demonstrates how selective suppression of feedback transmission allows this combination of synaptic function. During learning, sensory stimuli and the desired response are simultaneously presented as input to the network. Feedforward connections form self-organized representations of input, while suppressed feedback connections learn the transpose of the feedforward connectivity. During recall, suppression of transmission is removed, input activates the self-organized representation, and activity settles into a learned solution to the problem. This computational model can be used for learning of problems which are not linearly separable, including the negative patterning task (the XOR problem). Experiments in brain slice preparations of the rat somatosensory cortex tested whether the combination of self-organization and associative memory function could be provided by cholinergic suppression selective for feedback versus feedforward synapses. The cholinergic agonist carbachol selectively suppressed synaptic potentials elicited by stimulation of layer I (which contains a high percentage of feedback synapses), while having no effect on synaptic potentials elicited by stimulation of layer IV (with a high percentage of afferent and feedforward synapses).
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Affiliation(s)
- M E Hasselmo
- Department of Psychology, Harvard University, Cambridge, MA 02138, USA.
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46
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Tang AC, Hasselmo ME. Effect of long term baclofen treatment on recognition memory and novelty detection. Behav Brain Res 1996; 74:145-52. [PMID: 8851923 DOI: 10.1016/0166-4328(95)00038-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We studied the effect of long term baclofen treatment on recognition memory and novelty detection in rats using a habituation paradigm in an open field setting. Rats pretreated with 3 weeks' daily baclofen injection (0, 2 and 5 mg/kg) were tested in four 10 min sessions (familiarization session and three testing sessions: S1, S2 and S3) with 10-min intersession intervals. During S1, S2 and S3, rats were repeatedly exposed to the same two odor stimuli. During S3, for half of the rats in each treatment group, the spatial locations of the two stimuli were switched (Change) and for the other half the stimuli were replaced in the same locations (No Change). Two habituation scores were measured for each subject: H1 = N1 - N2; H2 = N2 - N3 (Ni the number of contacts made during Si). Baclofen at the highest dose (5 mg/kg) reduced the amount of habituation between S1 and S2 (H1) and increased responses to novel spatial arrangement, measured as the difference between H2 for the No-Change and Change groups. These results suggest a simultaneous impairment of recognition memory and enhancement of spatial novelty detection.
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Affiliation(s)
- A C Tang
- Department of Psychology, Harvard University, Cambridge, MA 02138, USA
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47
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Hasselmo ME, Wyble BP, Wallenstein GV. Encoding and retrieval of episodic memories: role of cholinergic and GABAergic modulation in the hippocampus. Hippocampus 1996; 6:693-708. [PMID: 9034856 DOI: 10.1002/(sici)1098-1063(1996)6:6<693::aid-hipo12>3.0.co;2-w] [Citation(s) in RCA: 232] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This research focuses on linking episodic memory function to the cellular physiology of hippocampal neurons, with a particular emphasis on modulatory effects at cholinergic and gamma-aminobutyric acid B receptors. Drugs which block acetylcholine receptors (e.g., scopolamine) have been shown to impair encoding of new information in humans, nonhuman primates, and rodents. Extensive data have been gathered about the cellular effects of acetylcholine in the hippocampus. In this research, models of individual hippocampal subregions have been utilized to understand the significance of particular features of modulation, and these hippocampal subregions have been combined in a network simulation which can replicate the selective encoding impairment produced by scopolamine in human subjects.
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Affiliation(s)
- M E Hasselmo
- Department of Psychology, Harvard University, Cambridge, Massachusetts 02138, USA
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Abstract
Neuromodulators including acetylcholine, norepinephrine, serotonin, dopamine and a range of peptides alter the processing characteristics of cortical networks through effects on excitatory and inhibitory synaptic transmission, on the adaptation of cortical pyramidal cells, on membrane potential, on the rate of synaptic modification, and on other cortical parameters. Computational models of self-organization and associative memory function in cortical structures such as the hippocampus, piriform cortex and neocortex provide a theoretical framework in which the role of these neuromodulatory effects can be analyzed. Neuromodulators such as acetylcholine and norepinephrine appear to enhance the influence of synapses from afferent fibers arising outside the cortex relative to the synapses of intrinsic and association fibers arising from other cortical pyramidal cells. This provides a continuum between a predominant influence of external stimulation to a predominant influence of internal recall (extrinsic vs. intrinsic). Modulatory influence along this continuum may underlie effects described in terms of learning and memory, signal to noise ratio, and attention.
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Affiliation(s)
- M E Hasselmo
- Department of Psychology, Harvard University, Cambridge, MA 02138, USA
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