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Vazquez JI, Gascue V, Quintana L, Migliaro A. Understanding daily rhythms in weakly electric fish: the role of melatonin on the electric behavior of Brachyhypopomus gauderio. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024; 210:7-18. [PMID: 37002418 DOI: 10.1007/s00359-023-01626-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 03/16/2023] [Accepted: 03/20/2023] [Indexed: 04/03/2023]
Abstract
Living organisms display molecular, physiological and behavioral rhythms synchronized with natural environmental cycles. Understanding the interaction between environment, physiology and behavior requires taking into account the complexity of natural habitats and the diversity of behavioral and physiological adaptations. Brachyhypopomus gauderio is characterized by the emission of electric organ discharges (EOD), with a very stable rate modulated by social and environmental cues. The nocturnal arousal in B. gauderio coincides with a melatonin-dependent EOD rate increase. Here, we first show a daily cycle in both the EOD basal rate (EOD-BR) and EOD-BR variability of B. gauderio in nature. We approached the understanding of the role of melatonin in this natural behavior through both behavioral pharmacology and in vitro assays. We report, for the first time in gymnotiformes, a direct effect of melatonin on the pacemaker nucleus (PN) in in vitro preparation. Melatonin treatment lowered EOD-BR in freely moving fish and PN basal rate, while increasing the variability of both. These results show that melatonin plays a key role in modulating the electric behavior of B. gauderio through its effect on rate and variability, both of which must be under a tight temporal regulation to prepare the animal for the challenging nocturnal environment.
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Affiliation(s)
- Juan I Vazquez
- Dpto de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay
| | - Valentina Gascue
- Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Laura Quintana
- Dpto de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay
| | - Adriana Migliaro
- Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
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2
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Abstract
The electric organ discharges (EODs) produced by weakly electric fish have long been a source of scientific intrigue and inspiration. The study of these species has contributed to our understanding of the organization of fixed action patterns, as well as enriching general imaging theory by unveiling the dual impact of an agent's actions on the environment and its own sensory system during the imaging process. This Centenary Review firstly compares how weakly electric fish generate species- and sex-specific stereotyped electric fields by considering: (1) peripheral mechanisms, including the geometry, channel repertoire and innervation of the electrogenic units; (2) the organization of the electric organs (EOs); and (3) neural coordination mechanisms. Secondly, the Review discusses the threefold function of the fish-centered electric fields: (1) to generate electric signals that encode the material, geometry and distance of nearby objects, serving as a short-range sensory modality or 'electric touch'; (2) to mark emitter identity and location; and (3) to convey social messages encoded in stereotypical modulations of the electric field that might be considered as species-specific communication symbols. Finally, this Review considers a range of potential research directions that are likely to be productive in the future.
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Affiliation(s)
- Angel Ariel Caputi
- Sistema Nacional de Investigadores - Uruguay, Av. Wilson Ferreira Aldunate 1219, Pando, PC 15600, Uruguay
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3
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Ilieş I, Zupanc GKH. Computational modeling predicts regulation of central pattern generator oscillations by size and density of the underlying heterogenous network. J Comput Neurosci 2023; 51:87-105. [PMID: 36201129 DOI: 10.1007/s10827-022-00835-7] [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: 08/29/2021] [Revised: 09/12/2022] [Accepted: 09/18/2022] [Indexed: 01/18/2023]
Abstract
Central pattern generators are characterized by a heterogeneous cellular composition, with different cell types playing distinct roles in the production and transmission of rhythmic signals. However, little is known about the functional implications of individual variation in the relative distributions of cells and their connectivity patterns. Here, we addressed this question through a combination of morphological data analysis and computational modeling, using the pacemaker nucleus of the weakly electric fish Apteronotus leptorhynchus as case study. A neural network comprised of 60-110 interconnected pacemaker cells and 15-30 relay cells conveying its output to electromotoneurons in the spinal cord, this nucleus continuously generates neural signals at frequencies of up to 1 kHz with high temporal precision. We systematically explored the impact of network size and density on oscillation frequencies and their variation within and across cells. To accurately determine effect sizes, we minimized the likelihood of complex dynamics using a simplified setup precluding differential delays. To identify natural constraints, parameter ranges were extended beyond experimentally recorded numbers of cells and connections. Simulations revealed that pacemaker cells have higher frequencies and lower within-population variability than relay cells. Within-cell precision and between-cells frequency synchronization increased with the number of pacemaker cells and of connections of either type, and decreased with relay cell count in both populations. Network-level frequency-synchronized oscillations occurred in roughly half of simulations, with maximized likelihood and firing precision within biologically observed parameter ranges. These findings suggest the structure of the biological pacemaker nucleus is optimized for generating synchronized sustained oscillations.
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Affiliation(s)
- Iulian Ilieş
- Laboratory of Neurobiology, Department of Biology, Northeastern University, Boston, MA, 02115, USA
| | - Günther K H Zupanc
- Laboratory of Neurobiology, Department of Biology, Northeastern University, Boston, MA, 02115, USA.
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4
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Lareo A, Varona P, Rodriguez FB. Modeling the Sequential Pattern Variability of the Electromotor Command System of Pulse Electric Fish. Front Neuroinform 2022; 16:912654. [PMID: 35836729 PMCID: PMC9275807 DOI: 10.3389/fninf.2022.912654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 05/26/2022] [Indexed: 11/13/2022] Open
Abstract
Mormyridae, a family of weakly electric fish, use electric pulses for communication and for extracting information from the environment (active electroreception). The electromotor system controls the timing of pulse generation. Ethological studies have described several sequences of pulse intervals (SPIs) related to distinct behaviors (e.g., mating or exploratory behaviors). Accelerations, scallops, rasps, and cessations are four different SPI patterns reported in these fish, each showing characteristic stereotyped temporal structures. This article presents a computational model of the electromotor command circuit that reproduces a whole set of SPI patterns while keeping the same internal network configuration. The topology of the model is based on a simplified representation of the network with four neuron clusters (nuclei). An initial configuration was built to reproduce nucleus characteristics and network topology as described by detailed morphological and electrophysiological studies. Then, a methodology based on a genetic algorithm (GA) was developed and applied to tune the model connectivity parameters to automatically reproduce a whole set of patterns recorded from freely-behaving Gnathonemus petersii specimens. Robustness analyses of input variability were performed to discard overfitting and assess validity. Results show that the set of SPI patterns is consistently reproduced reaching a dynamic balance between synaptic properties in the network. This model can be used as a tool to test novel hypotheses regarding temporal structure in electrogeneration. Beyond the electromotor model itself, the proposed methodology can be adapted to fit models of other biological networks that also exhibit sequential patterns.
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Prox J, Seicol B, Qi H, Argall A, Araya N, Behnke N, Guo L. Toward living neuroprosthetics: developing a biological brain pacemaker as a living neuromodulatory implant for improving parkinsonian symptoms. J Neural Eng 2021; 18. [PMID: 34010821 DOI: 10.1088/1741-2552/ac02dd] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 05/19/2021] [Indexed: 12/21/2022]
Abstract
Objective.Therapeutic intervention for Parkinson's disease (PD) via deep brain stimulation (DBS) represents the current paradigm for managing the advanced stages of the disease in patients when treatment with pharmaceuticals becomes inadequate. Although DBS is the prevailing therapy in these cases, the overall effectiveness and reliability of DBS can be diminished over time due to hardware complications and biocompatibility issues with the electronic implants. To achieve a lifetime solution, we envision that the next generation of neural implants will be entirely 'biological' and 'autologous', both physically and functionally. Thus, in this study, we set forth toward developing a biological brain pacemaker for treating PD. Our focus is to investigate engineering strategies for creating a multicellular biological circuit that integrates innate biological design and function while incorporating principles of neuromodulation to create a biological mechanism for delivering high-frequency stimulation with cellular specificity.Approach.We engineer a 3D multicellular circuit design built entirely from biological and biocompatible components using established tissue engineering protocols to demonstrate the feasibility of creating a living neural implant. Furthermore, using 2D co-culture systems, we investigate the physiologically relevant parameters that would be necessary to further develop a therapeutic benefit of high-frequency stimulation with cellular specificity within our construct design.Main results.Our results demonstrate the feasibility of fabricating a 3D multicellular circuit device in an implantable form. Furthermore, we show we can organize cellular materials to create potential functional connections in normal physiological conditions, thus laying down the foundation of designing a high-frequency pacing system for selective and controlled therapeutic neurostimulation.Significance.The findings from this study may lead to the future development of autologous living neural implants that both circumvent the issues inherent in electronic neural implants and form more biocompatible devices with lifelong robustness to repair and restore motor functions, with the ultimate benefit for patients with PD.
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Affiliation(s)
- Jordan Prox
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH, United States of America
| | - Benjamin Seicol
- Department of Neuroscience, The Ohio State University, Columbus, OH, United States of America
| | - Hao Qi
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States of America
| | - Aaron Argall
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH, United States of America
| | - Neway Araya
- Department of Neuroscience, The Ohio State University, Columbus, OH, United States of America
| | - Nicholas Behnke
- Department of Food, Agricultural and Biological Engineering, The Ohio State University, Columbus, OH, United States of America
| | - Liang Guo
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, United States of America
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6
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Modeling of sustained spontaneous network oscillations of a sexually dimorphic brainstem nucleus: the role of potassium equilibrium potential. J Comput Neurosci 2021; 49:419-439. [PMID: 34032982 DOI: 10.1007/s10827-021-00789-2] [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: 03/04/2021] [Revised: 04/15/2021] [Accepted: 04/29/2021] [Indexed: 10/21/2022]
Abstract
Intrinsic oscillators in the central nervous system play a preeminent role in the neural control of rhythmic behaviors, yet little is known about how the ionic milieu regulates their output patterns. A powerful system to address this question is the pacemaker nucleus of the weakly electric fish Apteronotus leptorhynchus. A neural network comprised of an average of 87 pacemaker cells and 20 relay cells produces tonic oscillations, with higher frequencies in males compared to females. Previous empirical studies have suggested that this sexual dimorphism develops and is maintained through modulation of buffering of extracellular K+ by a massive meshwork of astrocytes enveloping the pacemaker and relay cells. Here, we constructed a model of this neural network that can generate sustained spontaneous oscillations. Sensitivity analysis revealed the potassium equilibrium potential, EK (as a proxy of extracellular K+ concentration), and corresponding somatic channel conductances as critical determinants of oscillation frequency and amplitude. In models of both the pacemaker nucleus network and isolated pacemaker and relay cells, the frequency increased almost linearly with EK, whereas the amplitude decreased nonlinearly with increasing EK. Our simulations predict that this frequency increase is largely caused by a shift in the minimum K+ conductance over one oscillation period. This minimum is close to zero at more negative EK, converging to the corresponding maximum at less negative EK. This brings the resting membrane potential closer to the threshold potential at which voltage-gated Na+ channels become active, increasing the excitability, and thus the frequency, of pacemaker and relay cells.
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7
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Chagnaud BP, Perelmuter JT, Forlano PM, Bass AH. Gap junction-mediated glycinergic inhibition ensures precise temporal patterning in vocal behavior. eLife 2021; 10:e59390. [PMID: 33721553 PMCID: PMC7963477 DOI: 10.7554/elife.59390] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 02/28/2021] [Indexed: 01/30/2023] Open
Abstract
Precise neuronal firing is especially important for behaviors highly dependent on the correct sequencing and timing of muscle activity patterns, such as acoustic signaling. Acoustic signaling is an important communication modality for vertebrates, including many teleost fishes. Toadfishes are well known to exhibit high temporal fidelity in synchronous motoneuron firing within a hindbrain network directly determining the temporal structure of natural calls. Here, we investigated how these motoneurons maintain synchronous activation. We show that pronounced temporal precision in population-level motoneuronal firing depends on gap junction-mediated, glycinergic inhibition that generates a period of reduced probability of motoneuron activation. Super-resolution microscopy confirms glycinergic release sites formed by a subset of adjacent premotoneurons contacting motoneuron somata and dendrites. In aggregate, the evidence supports the hypothesis that gap junction-mediated, glycinergic inhibition provides a timing mechanism for achieving synchrony and temporal precision in the millisecond range for rapid modulation of acoustic waveforms.
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Affiliation(s)
| | | | - Paul M Forlano
- Department of Biology, Brooklyn College, City University of New YorkBrooklyn, NYUnited States
- Subprograms in Behavioral and Cognitive Neuroscience, Neuroscience, and Ecology, Evolutionary Biology and Behavior, The Graduate Center, City University of New YorkNew York, NYUnited States
| | - Andrew H Bass
- Department of Neurobiology and Behavior, Cornell UniversityIthaca, NYUnited States
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8
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Mucha S, Chapman LJ, Krahe R. The weakly electric fish, Apteronotus albifrons, actively avoids experimentally induced hypoxia. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2021; 207:369-379. [PMID: 33751182 PMCID: PMC8079295 DOI: 10.1007/s00359-021-01470-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 02/16/2021] [Accepted: 02/18/2021] [Indexed: 11/15/2022]
Abstract
Anthropogenic environmental degradation has led to an increase in the frequency and prevalence of aquatic hypoxia (low dissolved oxygen concentration, DO), which may affect habitat quality for water-breathing fishes. The weakly electric black ghost knifefish, Apteronotus albifrons, is typically found in well-oxygenated freshwater habitats in South America. Using a shuttle-box design, we exposed juvenile A. albifrons to a stepwise decline in DO from normoxia (> 95% air saturation) to extreme hypoxia (10% air saturation) in one compartment and chronic normoxia in the other. On average, A. albifrons actively avoided the hypoxic compartment below 22% air saturation. Hypoxia avoidance was correlated with upregulated swimming activity. Following avoidance, fish regularly ventured back briefly into deep hypoxia. Hypoxia did not affect the frequency of their electric organ discharges. Our results show that A. albifrons is able to sense hypoxia at non-lethal levels and uses active avoidance to mitigate its adverse effects.
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Affiliation(s)
- Stefan Mucha
- Institute of Biology, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany.
| | - Lauren J Chapman
- Department of Biology, McGill University, Montreal, QC, H3A 1B1, Canada
| | - Rüdiger Krahe
- Institute of Biology, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany.,Department of Biology, McGill University, Montreal, QC, H3A 1B1, Canada
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9
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Shifman AR, Sun Y, Benoit CM, Lewis JE. Dynamics of a neuronal pacemaker in the weakly electric fish Apteronotus. Sci Rep 2020; 10:16707. [PMID: 33028878 PMCID: PMC7542169 DOI: 10.1038/s41598-020-73566-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 09/14/2020] [Indexed: 12/04/2022] Open
Abstract
The precise timing of neuronal activity is critical for normal brain function. In weakly electric fish, the medullary pacemaker network (PN) sets the timing for an oscillating electric organ discharge (EOD) used for electric sensing. This network is the most precise biological oscillator known, with sub-microsecond variation in oscillator period. The PN consists of two principle sets of neurons, pacemaker and relay cells, that are connected by gap junctions and normally fire in synchrony, one-to-one with each EOD cycle. However, the degree of gap junctional connectivity between these cells appears insufficient to provide the population averaging required for the observed temporal precision of the EOD. This has led to the hypothesis that individual cells themselves fire with high precision, but little is known about the oscillatory dynamics of these pacemaker cells. As a first step towards testing this hypothesis, we have developed a biophysical model of a pacemaker neuron action potential based on experimental recordings. We validated the model by comparing the changes in oscillatory dynamics produced by different experimental manipulations. Our results suggest that this relatively simple model can capture a large range of channel dynamics exhibited by pacemaker cells, and will thus provide a basis for future work on network synchrony and precision.
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Affiliation(s)
- Aaron R Shifman
- Department of Biology, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada. .,Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada. .,uOttawa Brain and Mind Research Institute, Ottawa, Ontario, K1H 8M5, Canada.
| | - Yiren Sun
- Department of Biology, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.,Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.,uOttawa Brain and Mind Research Institute, Ottawa, Ontario, K1H 8M5, Canada
| | - Chloé M Benoit
- Department of Biology, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.,Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.,uOttawa Brain and Mind Research Institute, Ottawa, Ontario, K1H 8M5, Canada
| | - John E Lewis
- Department of Biology, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.,Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada.,uOttawa Brain and Mind Research Institute, Ottawa, Ontario, K1H 8M5, Canada
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10
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Costa RM, Baxter DA, Byrne JH. Computational model of the distributed representation of operant reward memory: combinatoric engagement of intrinsic and synaptic plasticity mechanisms. ACTA ACUST UNITED AC 2020; 27:236-249. [PMID: 32414941 PMCID: PMC7233148 DOI: 10.1101/lm.051367.120] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Accepted: 02/13/2020] [Indexed: 01/15/2023]
Abstract
Operant reward learning of feeding behavior in Aplysia increases the frequency and regularity of biting, as well as biases buccal motor patterns (BMPs) toward ingestion-like BMPs (iBMPs). The engram underlying this memory comprises cells that are part of a central pattern generating (CPG) circuit and includes increases in the intrinsic excitability of identified cells B30, B51, B63, and B65, and increases in B63-B30 and B63-B65 electrical synaptic coupling. To examine the ways in which sites of plasticity (individually and in combination) contribute to memory expression, a model of the CPG was developed. The model included conductance-based descriptions of cells CBI-2, B4, B8, B20, B30, B31, B34, B40, B51, B52, B63, B64, and B65, and their synaptic connections. The model generated patterned activity that resembled physiological BMPs, and implementation of the engram reproduced increases in frequency, regularity, and bias. Combined enhancement of B30, B63, and B65 excitabilities increased BMP frequency and regularity, but not bias toward iBMPs. Individually, B30 increased regularity and bias, B51 increased bias, B63 increased frequency, and B65 decreased all three BMP features. Combined synaptic plasticity contributed primarily to regularity, but also to frequency and bias. B63-B30 coupling contributed to regularity and bias, and B63-B65 coupling contributed to all BMP features. Each site of plasticity altered multiple BMP features simultaneously. Moreover, plasticity loci exhibited mutual dependence and synergism. These results indicate that the memory for operant reward learning emerged from the combinatoric engagement of multiple sites of plasticity.
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Affiliation(s)
- Renan M Costa
- Keck Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Anatomy, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas 77030, USA
| | - Douglas A Baxter
- Keck Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Anatomy, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Engineering in Medicine (EnMed), Texas A&M Health Science Center-Houston, Houston, Texas 77030, USA
| | - John H Byrne
- Keck Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Anatomy, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas 77030, USA
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11
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Crampton WGR. Electroreception, electrogenesis and electric signal evolution. JOURNAL OF FISH BIOLOGY 2019; 95:92-134. [PMID: 30729523 DOI: 10.1111/jfb.13922] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 02/05/2019] [Indexed: 05/06/2023]
Abstract
Electroreception, the capacity to detect external underwater electric fields with specialised receptors, is a phylogenetically widespread sensory modality in fishes and amphibians. In passive electroreception, a capacity possessed by c. 16% of fish species, an animal uses low-frequency-tuned ampullary electroreceptors to detect microvolt-range bioelectric fields from prey, without the need to generate its own electric field. In active electroreception (electrolocation), which occurs only in the teleost lineages Mormyroidea and Gymnotiformes, an animal senses its surroundings by generating a weak (< 1 V) electric-organ discharge (EOD) and detecting distortions in the EOD-associated field using high-frequency-tuned tuberous electroreceptors. Tuberous electroreceptors also detect the EODs of neighbouring fishes, facilitating electrocommunication. Several other groups of elasmobranchs and teleosts generate weak (< 10 V) or strong (> 50 V) EODs that facilitate communication or predation, but not electrolocation. Approximately 1.5% of fish species possess electric organs. This review has two aims. First, to synthesise our knowledge of the functional biology and phylogenetic distribution of electroreception and electrogenesis in fishes, with a focus on freshwater taxa and with emphasis on the proximate (morphological, physiological and genetic) bases of EOD and electroreceptor diversity. Second, to describe the diversity, biogeography, ecology and electric signal diversity of the mormyroids and gymnotiforms and to explore the ultimate (evolutionary) bases of signal and receptor diversity in their convergent electrogenic-electrosensory systems. Four sets of potential drivers or moderators of signal diversity are discussed. First, selective forces of an abiotic (environmental) nature for optimal electrolocation and communication performance of the EOD. Second, selective forces of a biotic nature targeting the communication function of the EOD, including sexual selection, reproductive interference from syntopic heterospecifics and selection from eavesdropping predators. Third, non-adaptive drift and, finally, phylogenetic inertia, which may arise from stabilising selection for optimal signal-receptor matching.
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12
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Hasegawa Y, Van Vu T. Uncertainty relations in stochastic processes: An information inequality approach. Phys Rev E 2019; 99:062126. [PMID: 31330674 DOI: 10.1103/physreve.99.062126] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Indexed: 06/10/2023]
Abstract
The thermodynamic uncertainty relation is an inequality stating that it is impossible to attain higher precision than the bound defined by entropy production. In statistical inference theory, information inequalities assert that it is infeasible for any estimator to achieve an error smaller than the prescribed bound. Inspired by the similarity between the thermodynamic uncertainty relation and the information inequalities, we apply the latter to systems described by Langevin equations, and we derive the bound for the fluctuation of thermodynamic quantities. When applying the Cramér-Rao inequality, the obtained inequality reduces to the fluctuation-response inequality. We find that the thermodynamic uncertainty relation is a particular case of the Cramér-Rao inequality, in which the Fisher information is the total entropy production. Using the equality condition of the Cramér-Rao inequality, we find that the stochastic total entropy production is the only quantity that can attain equality in the thermodynamic uncertainty relation. Furthermore, we apply the Chapman-Robbins inequality and obtain a relation for the lower bound of the ratio between the variance and the sensitivity of systems in response to arbitrary perturbations.
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Affiliation(s)
- Yoshihiko Hasegawa
- Department of Information and Communication Engineering, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan
| | - Tan Van Vu
- Department of Information and Communication Engineering, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan
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13
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Zupanc GKH, Amaro SM, Lehotzky D, Zupanc FB, Leung NY. Glia-mediated modulation of extracellular potassium concentration determines the sexually dimorphic output frequency of a model brainstem oscillator. J Theor Biol 2019; 471:117-124. [PMID: 30902592 DOI: 10.1016/j.jtbi.2019.03.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 03/05/2019] [Accepted: 03/19/2019] [Indexed: 10/27/2022]
Abstract
Sexual dimorphism in behavior is widespread among animals, but the cellular mechanisms underlying neural control of this phenomenon are largely unknown. One behavior that has provided some important clues about how such sex differences might develop is the electric organ discharge of Apteronotus leptorhynchus. In this weakly electric fish, the mean discharge frequencies of males and females are 880 Hz and 740 Hz, respectively, with little overlap of the two frequency bands. The discharges are controlled, in a one-to-one fashion, by the neural oscillations of the pacemaker nucleus in the medulla oblongata. Experimental evidence has shown that the astrocytic syncytium associated with the neural network that generates these oscillations is significantly larger, and stronger coupled via gap junctions, in females than in males. In the present study, modeling of this network was performed to test the hypotheses that the sex-dependent differences in the structure and properties of the astrocytic syncytium mediate better buffering of extracellular potassium in females than in males, which in turn causes, via a lowering of the potassium equilibrium potential, a decrease in the oscillation frequency. Simulations of the neural activity of the pacemaker nucleus and its individual components demonstrated that under both spontaneous and induced conditions the oscillation frequency and the potassium equilibrium potential are strongly positively correlated. These simulations predict that sufficient separation of the electric organ discharge frequencies for establishment of the sexual dimorphism can be achieved by rather minor alterations in the concentration of the extracellular potassium concentration in the pacemaker nucleus.
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Affiliation(s)
- Günther K H Zupanc
- Laboratory of Neurobiology, Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
| | - Stephanie M Amaro
- Laboratory of Neurobiology, Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Dávid Lehotzky
- Laboratory of Neurobiology, Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Frederick B Zupanc
- Laboratory of Neurobiology, Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Nicholas Y Leung
- Laboratory of Neurobiology, Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
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14
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Lucas KM, Warrington J, Lewis TJ, Lewis JE. Neuronal Dynamics Underlying Communication Signals in a Weakly Electric Fish: Implications for Connectivity in a Pacemaker Network. Neuroscience 2019; 401:21-34. [PMID: 30641115 DOI: 10.1016/j.neuroscience.2019.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 12/19/2018] [Accepted: 01/04/2019] [Indexed: 11/19/2022]
Abstract
Neuronal networks can produce stable oscillations and synchrony that are under tight control yet flexible enough to rapidly switch between dynamical states. The pacemaker nucleus in the weakly electric fish comprises a network of electrically coupled neurons that fire synchronously at high frequency. This activity sets the timing for an oscillating electric organ discharge with the lowest cycle-to-cycle variability of all known biological oscillators. Despite this high temporal precision, pacemaker activity is behaviorally modulated on millisecond time-scales for the generation of electrocommunication signals. The network mechanisms that allow for this combination of stability and flexibility are not well understood. In this study, we use an in vitro pacemaker preparation from Apteronotus leptorhynchus to characterize the neural responses elicited by the synaptic inputs underlying electrocommunication. These responses involve a variable increase in firing frequency and a prominent desynchronization of neurons that recovers within 5 oscillation cycles. Using a previously developed computational model of the pacemaker network, we show that the frequency changes and rapid resynchronization observed experimentally are most easily explained when model neurons are interconnected more densely and with higher coupling strengths than suggested by published data. We suggest that the pacemaker network achieves both stability and flexibility by balancing coupling strength with interconnectivity and that variation in these network features may provide a substrate for species-specific evolution of electrocommunication signals.
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Affiliation(s)
- Kathleen M Lucas
- Department of Biology, University of Ottawa, Ottawa K1N 6N5, Canada
| | - Julie Warrington
- Department of Biology, University of Ottawa, Ottawa K1N 6N5, Canada
| | - Timothy J Lewis
- Department of Mathematics, University of California Davis, Davis, CA 95616, USA
| | - John E Lewis
- Department of Biology, University of Ottawa, Ottawa K1N 6N5, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa K1N 6N5, Canada.
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15
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Smith GT, Proffitt MR, Smith AR, Rusch DB. Genes linked to species diversity in a sexually dimorphic communication signal in electric fish. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 204:93-112. [PMID: 29058069 DOI: 10.1007/s00359-017-1223-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 09/17/2017] [Accepted: 09/25/2017] [Indexed: 02/06/2023]
Abstract
Sexually dimorphic behaviors are often regulated by androgens and estrogens. Steroid receptors and metabolism are control points for evolutionary changes in sexual dimorphism. Electric communication signals of South American knifefishes are a model for understanding the evolution and physiology of sexually dimorphic behavior. These signals are regulated by gonadal steroids and controlled by a simple neural circuit. Sexual dimorphism of the signals varies across species. We used transcriptomics to examine mechanisms for sex differences in electric organ discharges (EODs) of two closely related species, Apteronotus leptorhynchus and Apteronotus albifrons, with reversed sexual dimorphism in their EODs. The pacemaker nucleus (Pn), which controls EOD frequency (EODf), expressed transcripts for steroid receptors and metabolizing enzymes, including androgen receptors, estrogen receptors, aromatase, and 5α-reductase. The Pn expressed mRNA for ion channels likely to regulate the high-frequency activity of Pn neurons and for neuromodulator and neurotransmitter receptors that may regulate EOD modulations used in aggression and courtship. Expression of several ion channel genes, including those for Kir3.1 inward-rectifying potassium channels and sodium channel β1 subunits, was sex-biased or correlated with EODf in ways consistent with EODf sex differences. Our findings provide a basis for future studies to characterize neurogenomic mechanisms by which sex differences evolve.
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Affiliation(s)
- G Troy Smith
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA. .,Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA.
| | - Melissa R Proffitt
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA.,Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - Adam R Smith
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA.,Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - Douglas B Rusch
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA.,Center for Genomics and Bioinformatics, Indiana University, Bloomington, IN, 47405, USA
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16
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Sakurai A, Katz PS. The central pattern generator underlying swimming in Dendronotus iris: a simple half-center network oscillator with a twist. J Neurophysiol 2016; 116:1728-1742. [PMID: 27440239 DOI: 10.1152/jn.00150.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 07/14/2016] [Indexed: 11/22/2022] Open
Abstract
The nudibranch mollusc, Dendronotus iris, swims by rhythmically flexing its body from left to right. We identified a bilaterally represented interneuron, Si3, that provides strong excitatory drive to the previously identified Si2, forming a half-center oscillator, which functions as the central pattern generator (CPG) underlying swimming. As with Si2, Si3 inhibited its contralateral counterpart and exhibited rhythmic bursts in left-right alternation during the swim motor pattern. Si3 burst almost synchronously with the contralateral Si2 and was coactive with the efferent impulse activity in the contralateral body wall nerve. Perturbation of bursting in either Si3 or Si2 by current injection halted or phase-shifted the swim motor pattern, suggesting that they are both critical CPG members. Neither Si2 nor Si3 exhibited endogenous bursting properties when activated alone; activation of all four neurons was necessary to initiate and maintain the swim motor pattern. Si3 made a strong excitatory synapse onto the contralateral Si2 to which it is also electrically coupled. When Si3 was firing tonically but not exhibiting bursting, artificial enhancement of the Si3-to-Si2 synapse using dynamic clamp caused all four neurons to burst. In contrast, negation of the Si3-to-Si2 synapse by dynamic clamp blocked ongoing swim motor patterns. Together, these results suggest that the Dendronotus swim CPG is organized as a "twisted" half-center oscillator in which each "half" is composed of two excitatory-coupled neurons from both sides of the brain, each of which inhibits its contralateral counterpart. Consisting of only four neurons, this is perhaps the simplest known network oscillator for locomotion.
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Affiliation(s)
- Akira Sakurai
- Neuroscience Institute, Georgia State University, Atlanta, Georgia
| | - Paul S Katz
- Neuroscience Institute, Georgia State University, Atlanta, Georgia
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17
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Mori F, Mikhailov AS. Precision of collective oscillations in complex dynamical systems with noise. Phys Rev E 2016; 93:062206. [PMID: 27415254 DOI: 10.1103/physreve.93.062206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Indexed: 11/07/2022]
Abstract
Two kinds of oscillation precision are investigated for complex oscillatory dynamical systems under action of noise. The many-cycle precision determined by the variance of the times needed for a large number of cycles is closely related to diffusion of the global oscillation phase and provides an invariant property of a system. The single-cycle precision given by the variance in durations of single cycles is sensitive to the choice of an output variable and output checkpoint; it can be improved by an appropriate selection of them. A general analysis of the precision properties based on the Floquet perturbation theory is performed and analytical predictions are verified in numerical simulations of a model oscillatory genetic network.
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Affiliation(s)
- Fumito Mori
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Alexander S Mikhailov
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany.,Department of Mathematical and Life Sciences, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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18
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Nogueira J, Caputi AA. From the intrinsic properties to the functional role of a neuron phenotype: an example from electric fish during signal trade-off. ACTA ACUST UNITED AC 2014; 216:2380-92. [PMID: 23761463 DOI: 10.1242/jeb.082651] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This review deals with the question: what is the relationship between the properties of a neuron and the role that the neuron plays within a given neural circuit? Answering this kind of question requires collecting evidence from multiple neuron phenotypes and comparing the role of each type in circuits that perform well-defined computational tasks. The focus here is on the spherical neurons in the electrosensory lobe of the electric fish Gymnotus omarorum. They belong to the one-spike-onset phenotype expressed at the early stages of signal processing in various sensory modalities and diverse taxa. First, we refer to the one-spike neuron intrinsic properties, their foundation on a low-threshold K(+) conductance, and the potential roles of this phenotype in different circuits within a comparative framework. Second, we present a brief description of the active electric sense of weakly electric fish and the particularities of spherical one-spike-onset neurons in the electrosensory lobe of G. omarorum. Third, we introduce one of the specific tasks in which these neurons are involved: the trade-off between self- and allo-generated signals. Fourth, we discuss recent evidence indicating a still-undescribed role for the one-spike phenotype. This role deals with the blockage of the pathway after being activated by the self-generated electric organ discharge and how this blockage favors self-generated electrosensory information in the context of allo-generated interference. Based on comparative analysis we conclude that one-spike-onset neurons may play several functional roles in animal sensory behavior. There are specific adaptations of the neuron's 'response function' to the circuit and task. Conversely, the way in which a task is accomplished depends on the intrinsic properties of the neurons involved. In short, the role of a neuron within a circuit depends on the neuron and its functional context.
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Affiliation(s)
- Javier Nogueira
- Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Avenida General Flores, 2125 Montevideo, Uruguay
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Salazar VL, Krahe R, Lewis JE. The energetics of electric organ discharge generation in gymnotiform weakly electric fish. ACTA ACUST UNITED AC 2014; 216:2459-68. [PMID: 23761471 DOI: 10.1242/jeb.082735] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Gymnotiform weakly electric fish produce an electric signal to sense their environment and communicate with conspecifics. Although the generation of such relatively large electric signals over an entire lifetime is expected to be energetically costly, supporting evidence to date is equivocal. In this article, we first provide a theoretical analysis of the energy budget underlying signal production. Our analysis suggests that wave-type and pulse-type species invest a similar fraction of metabolic resources into electric signal generation, supporting previous evidence of a trade-off between signal amplitude and frequency. We then consider a comparative and evolutionary framework in which to interpret and guide future studies. We suggest that species differences in signal generation and plasticity, when considered in an energetics context, will not only help to evaluate the role of energetic constraints in the evolution of signal diversity but also lead to important general insights into the energetics of bioelectric signal generation.
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Affiliation(s)
- Vielka L Salazar
- Department of Biology, Cape Breton University, Sydney, NS, Canada, B1P 6L2
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20
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Vardi R, Goldental A, Guberman S, Kalmanovich A, Marmari H, Kanter I. Sudden synchrony leaps accompanied by frequency multiplications in neuronal activity. Front Neural Circuits 2013; 7:176. [PMID: 24198764 PMCID: PMC3812537 DOI: 10.3389/fncir.2013.00176] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 10/13/2013] [Indexed: 01/01/2023] Open
Abstract
A classical view of neural coding relies on temporal firing synchrony among functional groups of neurons, however, the underlying mechanism remains an enigma. Here we experimentally demonstrate a mechanism where time-lags among neuronal spiking leap from several tens of milliseconds to nearly zero-lag synchrony. It also allows sudden leaps out of synchrony, hence forming short epochs of synchrony. Our results are based on an experimental procedure where conditioned stimulations were enforced on circuits of neurons embedded within a large-scale network of cortical cells in vitro and are corroborated by simulations of neuronal populations. The underlying biological mechanisms are the unavoidable increase of the neuronal response latency to ongoing stimulations and temporal or spatial summation required to generate evoked spikes. These sudden leaps in and out of synchrony may be accompanied by multiplications of the neuronal firing frequency, hence offering reliable information-bearing indicators which may bridge between the two principal neuronal coding paradigms.
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Affiliation(s)
- Roni Vardi
- Gonda Interdisciplinary Brain Research Center and the Goodman Faculty of Life Sciences, Bar-Ilan UniversityRamat-Gan, Israel
| | - Amir Goldental
- Department of Physics, Bar-Ilan UniversityRamat-Gan, Israel
| | - Shoshana Guberman
- Gonda Interdisciplinary Brain Research Center and the Goodman Faculty of Life Sciences, Bar-Ilan UniversityRamat-Gan, Israel
- Department of Physics, Bar-Ilan UniversityRamat-Gan, Israel
| | - Alexander Kalmanovich
- Gonda Interdisciplinary Brain Research Center and the Goodman Faculty of Life Sciences, Bar-Ilan UniversityRamat-Gan, Israel
| | - Hagar Marmari
- Gonda Interdisciplinary Brain Research Center and the Goodman Faculty of Life Sciences, Bar-Ilan UniversityRamat-Gan, Israel
| | - Ido Kanter
- Gonda Interdisciplinary Brain Research Center and the Goodman Faculty of Life Sciences, Bar-Ilan UniversityRamat-Gan, Israel
- Department of Physics, Bar-Ilan UniversityRamat-Gan, Israel
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21
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Zhang D, Li Y, Wu S, Rasch MJ. Design principles of the sparse coding network and the role of "sister cells" in the olfactory system of Drosophila. Front Comput Neurosci 2013; 7:141. [PMID: 24167488 PMCID: PMC3806038 DOI: 10.3389/fncom.2013.00141] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 09/30/2013] [Indexed: 11/25/2022] Open
Abstract
Sensory systems face the challenge to represent sensory inputs in a way to allow easy readout of sensory information by higher brain areas. In the olfactory system of the fly drosopohila melanogaster, projection neurons (PNs) of the antennal lobe (AL) convert a dense activation of glomeruli into a sparse, high-dimensional firing pattern of Kenyon cells (KCs) in the mushroom body (MB). Here we investigate the design principles of the olfactory system of drosophila in regard to the capabilities to discriminate odor quality from the MB representation and its robustness to different types of noise. We focus on understanding the role of highly correlated homotypic projection neurons (“sister cells”) found in the glomeruli of flies. These cells are coupled by gap-junctions and receive almost identical sensory inputs, but target randomly different KCs in MB. We show that sister cells might play a crucial role in increasing the robustness of the MB odor representation to noise. Computationally, sister cells thus might help the system to improve the generalization capabilities in face of noise without impairing the discriminability of odor quality at the same time.
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Affiliation(s)
- Danke Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University Beijing, China ; School of Automation Science and Engineering, South China University of Technology Guangzhou, China
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22
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Hartbauer M, Siegert ME, Fertschai I, Römer H. Acoustic signal perception in a noisy habitat: lessons from synchronising insects. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2012; 198:397-409. [PMID: 22427234 PMCID: PMC3357476 DOI: 10.1007/s00359-012-0718-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 02/29/2012] [Accepted: 02/29/2012] [Indexed: 11/24/2022]
Abstract
Acoustically communicating animals often have to cope with ambient noise that has the potential to interfere with the perception of conspecific signals. Here we use the synchronous display of mating signals in males of the tropical katydid Mecopoda elongata in order to assess the influence of nocturnal rainforest noise on signal perception. Loud background noise may disturb chorus synchrony either by masking the signals of males or by interaction of noisy events with the song oscillator. Phase-locked synchrony of males was studied under various signal-to-noise ratios (SNRs) using either native noise or the audio component of noise (<9 kHz). Synchronous entrainment was lost at a SNR of −3 dB when native noise was used, whereas with the audio component still 50 % of chirp periods matched the pacer period at a SNR of −7 dB. Since the chirp period of solo singing males remained almost unaffected by noise, our results suggest that masking interference limits chorus synchrony by rendering conspecific signals ambiguous. Further, entrainment with periodic artificial signals indicates that synchrony is achieved by ignoring heterospecific signals and attending to a conspecific signal period. Additionally, the encoding of conspecific chirps was studied in an auditory neuron under the same background noise regimes.
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Affiliation(s)
- M Hartbauer
- Institute of Zoology, Karl-Franzens University Graz, Graz, Austria.
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23
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Kori H, Kawamura Y, Masuda N. Structure of cell networks critically determines oscillation regularity. J Theor Biol 2012; 297:61-72. [DOI: 10.1016/j.jtbi.2011.12.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/21/2011] [Accepted: 12/07/2011] [Indexed: 10/14/2022]
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24
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George AA, Macleod GT, Zakon HH. Calcium-dependent phosphorylation regulates neuronal stability and plasticity in a highly precise pacemaker nucleus. J Neurophysiol 2011; 106:319-31. [PMID: 21525377 PMCID: PMC3129731 DOI: 10.1152/jn.00741.2010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 04/21/2011] [Indexed: 12/24/2022] Open
Abstract
Specific types of neurons show stable, predictable excitability properties, while other neurons show transient adaptive plasticity of their excitability. However, little attention has been paid to how the cellular pathways underlying adaptive plasticity interact with those that maintain neuronal stability. We addressed this question in the pacemaker neurons from a weakly electric fish because these neurons show a highly stable spontaneous firing rate as well as an N-methyl-D-aspartate (NMDA) receptor-dependent form of plasticity. We found that basal firing rates were regulated by a serial interaction of conventional and atypical PKC isoforms and that this interaction establishes individual differences within the species. We observed that NMDA receptor-dependent plasticity is achieved by further activation of these kinases. Importantly, the PKC pathway is maintained in an unsaturated baseline state to allow further Ca(2+)-dependent activation during plasticity. On the other hand, the Ca(2+)/calmodulin-dependent phosphatase calcineurin does not regulate baseline firing but is recruited to control the duration of the NMDA receptor-dependent plasticity and return the pacemaker firing rate back to baseline. This work illustrates how neuronal plasticity can be realized by biasing ongoing mechanisms of stability (e.g., PKC) and terminated by recruiting alternative mechanisms (e.g., calcineurin) that constrain excitability. We propose this as a general model for regulating activity-dependent change in neuronal excitability.
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Affiliation(s)
- Andrew A George
- Section of Neurobiology and Institute for Neuroscience, Patterson Laboratory, University of Texas at Austin, Texas, USA.
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25
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Quintana L, Sierra F, Silva A, Macadar O. A central pacemaker that underlies the production of seasonal and sexually dimorphic social signals: functional aspects revealed by glutamate stimulation. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2010; 197:211-25. [DOI: 10.1007/s00359-010-0603-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 09/21/2010] [Accepted: 10/17/2010] [Indexed: 01/31/2023]
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Abstract
Weakly electric fishes emit electric organ discharges (EODs) from their tail electric organs and sense feedback signals from their EODs by electroreceptors in the skin. The electric sense is utilized for various behaviors, including electrolocation, electrocommunication, and the Jamming avoidance response (JAR). For each behavior, various types of sensory Information are embedded in the transient electrical signals produced by the fish. These temporal signals are sampled, encoded, and further processed by peripheral and central neurons specialized for time coding. There are time codes for the sex or species Identities of other fish or the resistance and capacitance of objects. In the central nervous system, specialized neural elements exist for decoding time codes for different behavioral functions. Comparative studies allow phylogenetic comparison of time-coding neural systems among weakly electric fishes.
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Affiliation(s)
- Masashi Kawasaki
- Department of Biology, Gilmer Hall, University of Virginia, Charlottesville, VA 22904, USA.
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27
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Maler L. Receptive field organization across multiple electrosensory maps. I. Columnar organization and estimation of receptive field size. J Comp Neurol 2009; 516:376-93. [DOI: 10.1002/cne.22124] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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28
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Li WC, Roberts A, Soffe SR. Locomotor rhythm maintenance: electrical coupling among premotor excitatory interneurons in the brainstem and spinal cord of young Xenopus tadpoles. J Physiol 2009; 587:1677-93. [PMID: 19221124 PMCID: PMC2683956 DOI: 10.1113/jphysiol.2008.166942] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Electrical coupling is important in rhythm generating systems. We examine its role in circuits controlling locomotion in a simple vertebrate model, the young Xenopus tadpole, where the hindbrain and spinal cord excitatory descending interneurons (dINs) that drive and maintain swimming have been characterised. Using simultaneous paired recordings, we show that most dINs are electrically coupled exclusively to other dINs (DC coupling coefficients ∼8.5%). The coupling shows typical low-pass filtering. We found no evidence that other swimming central pattern generator (CPG) interneurons are coupled to dINs or to each other. Electrical coupling potentials between dINs appear to contribute to their unusually reliable firing during swimming. To investigate the role of electrical coupling in swimming, we evaluated the specificity of gap junction blockers (18-β-GA, carbenoxolone, flufenamic acid and heptanol) in paired recordings. 18-β-GA at 40–60 μm produced substantial (84%) coupling block but few effects on cellular properties. Swimming episodes in 18-β-GA were significantly shortened (to ∼2% of control durations). At the same time, dIN firing reliability fell from nearly 100% to 62% of swimming cycles and spike synchronization weakened. Because dINs drive CPG neuron firing and are critical in maintaining swimming, the weakening of dIN activity could account for the effects of 18-β-GA on swimming. We conclude that electrical coupling among pre motor reticulospinal and spinal dINs, the excitatory interneurons that drive the swimming CPG in the hatchling Xenopus tadpole, may contribute to the maintenance of swimming as well as synchronization of activity.
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Affiliation(s)
- Wen-Chang Li
- School of Biology, University of St Andrews, Bute Medical Building, Fife KY16 9TS, Scotland, UK.
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29
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Abstract
The success of forward genetic (from phenotype to gene) approaches to uncover genes that drive the molecular mechanism of circadian clocks and control circadian behavior has been unprecedented. Links among genes, cells, neural circuits, and circadian behavior have been uncovered in the Drosophila and mammalian systems, demonstrating the feasibility of finding single genes that have major effects on behavior. Why was this approach so successful in the elucidation of circadian rhythms? This article explores the answers to this question and describes how the methods used successfully for identifying the molecular basis of circadian rhythms can be applied to other behaviors such as anxiety, addiction, and learning and memory.
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Affiliation(s)
- Joseph S Takahashi
- Howard Hughes Medical Institute, Northwestern University, Evanston, IL 60208, USA.
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30
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Oestreich J, Dembrow NC, George AA, Zakon HH. A "sample-and-hold" pulse-counting integrator as a mechanism for graded memory underlying sensorimotor adaptation. Neuron 2006; 49:577-88. [PMID: 16476666 DOI: 10.1016/j.neuron.2006.01.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 12/05/2005] [Accepted: 01/29/2006] [Indexed: 11/19/2022]
Abstract
The mechanisms behind the induction of cellular correlates of memory by sensory input and their contribution to meaningful behavioral changes are largely unknown. We previously reported a graded memory in the form of sensorimotor adaptation in the electromotor output of electric fish. Here we show that the mechanism for this adaptation is a synaptically induced long-lasting shift in intrinsic neuronal excitability. This mechanism rapidly integrates hundreds of spikes in a second, or gradually integrates the same number of spikes delivered over tens of minutes. Thus, this mechanism appears immune to frequency-dependent fluctuations in input and operates as a simple pulse counter over a wide range of time scales, enabling it to transduce graded sensory information into a graded memory and a corresponding change in the behavioral output. This adaptation is based on an NMDA receptor-mediated change in intrinsic excitability of the postsynaptic neurons involving the Ca2+-dependent activation of TRP channels.
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Affiliation(s)
- Jörg Oestreich
- Section of Neurobiology, The University of Texas at Austin, 1 University Station C0920, Austin, Texas 78712, USA
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31
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Sträng JE, Ostborn P. Wave patterns in frequency-entrained oscillator lattices. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:056137. [PMID: 16383718 DOI: 10.1103/physreve.72.056137] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Indexed: 05/05/2023]
Abstract
We study and classify firing waves in two-dimensional oscillator lattices. To do so, we simulate a pulse-coupled oscillator model aimed to resemble a group of pacemaker cells in the heart. The oscillators are assigned random natural frequencies, and we focus on frequency entrained states. Depending on the initial condition, three types of wave landscapes are seen asymptotically. A concentric landscape contains concentric waves with one or more foci. Spiral landscapes contain one or more spiral waves. A mixed landscape contains both concentric and spiral waves. Mixed landscapes are only seen for moderate coupling strengths g, since for higher g, spiral waves have higher frequency than concentric waves, so that they cannot mix in frequency entrained states. If the initial condition is random, the probability to get a concentric landscape increases with increasing coupling strength g, but decreases with increasing lattice size. The g dependence of the probability enables hysteresis, where the system jumps between the two landscape types as g is continuously changed. For moderate g, spiral tips rotate around a suppressed oscillator that never fires. We call such an oscillator an oscillator defect. A spiral may also rotate around a point defect situated between the oscillators. In that case all oscillators fire at the entrained frequency. For larger g, a spiral tip either moves around a row of suppressed oscillators, a row defect, or around an open curve situated between the oscillators, which may be called a line defect. The length of a row or line defect increases with g. Our results may help understand sinus node reentry, where the natural pacemaker of the heart suddenly shifts to a higher frequency. Some of the observed phenomena seem generic, based on simulations of other models.
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Affiliation(s)
- Jan Eric Sträng
- Abteilung Theoretische Physik, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany.
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32
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Fuentealba P, Crochet S, Timofeev I, Bazhenov M, Sejnowski TJ, Steriade M. Experimental evidence and modeling studies support a synchronizing role for electrical coupling in the cat thalamic reticular neurons in vivo. Eur J Neurosci 2004; 20:111-9. [PMID: 15245484 PMCID: PMC2905213 DOI: 10.1111/j.1460-9568.2004.03462.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thalamic reticular (RE) neurons are crucially implicated in brain rhythms. Here, we report that RE neurons of adult cats, recorded and stained intracellularly in vivo, displayed spontaneously occurring spikelets, which are characteristic of central neurons that are coupled electrotonically via gap junctions. Spikelets occurred spontaneously during spindles, an oscillation in which RE neurons play a leading role, as well as during interspindle lulls. They were significantly different from excitatory postsynaptic potentials and also distinct from fast prepotentials that are presumably dendritic spikes generated synaptically. Spikelets were strongly reduced by halothane, a blocker of gap junctions. Multi-site extracellular recordings performed before, during and after administration of halothane demonstrated a role for electrical coupling in the synchronization of spindling activity within the RE nucleus. Finally, computational models of RE neurons predicted that gap junctions between these neurons could mediate the spread of low-frequency activity at great distances. These experimental and modeling data suggest that electrotonic coupling within the RE nucleus plays an important role in the generation and synchronization of low-frequency (spindling) activities in the thalamus.
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Affiliation(s)
- Pablo Fuentealba
- Laboratory of Neurophysiology, Faculty of Medicine, Laval University, Quebec City, Canada G1K 7P4
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De Blasio BF, Iversen JG, Røttingen JA. Intercellular calcium signalling in cultured renal epithelia: a theoretical study of synchronization mode and pacemaker activity. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2004; 33:657-70. [PMID: 15565440 DOI: 10.1007/s00249-004-0409-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2003] [Revised: 02/24/2004] [Accepted: 04/05/2004] [Indexed: 11/27/2022]
Abstract
We investigate a two-dimensional lattice model representation of intercellular Ca2+ signalling in a population of epithelial cells coupled by gap junctions. The model is based on and compared with Ca2+ imaging data from globally bradykinin-stimulated MDCK-I (Madin-Darby canine kidney)-I cell layers. We study large-scale synchronization of relevance to our laboratory experiments. The system is found to express a wealth of dynamics, including quasiperiodic, chaotic and multiply-periodic behaviour for intermediate couplings. We take a particular interest in understanding the role of "pacemaker cells" in the synchronization process. It has been hypothesized that a few highly hormone-sensitive cells control the collective frequency of oscillation, which is close to the natural frequencies (without coupling) of these cells. The model behaviour is consistent with the conjectures of the pacemaker cell hypothesis near the critical coupling where the cells lock onto a single frequency. However, the simulations predict that the frequency in globally connected systems decreases with increasing coupling. It is found that a pacemaker is not defined by its natural frequency alone, but that other intrinsic or local factors must be considered. Inclusion of partly sensitized cells that do not oscillate autonomously in the cell layer increases the coupling necessary for global synchronization. For not excessively high coupling, these cells oscillate irregularly and with distinctive lower frequencies. In summary, the present study shows that the frequency of synchronized oscillations is not dictated by one or few fast-responding cells. The collective frequency is the result of a two-way communication between the phase-advanced pacemaker and its environment.
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Zupanc GKH. From oscillators to modulators: behavioral and neural control of modulations of the electric organ discharge in the gymnotiform fish, Apteronotus leptorhynchus. ACTA ACUST UNITED AC 2004; 96:459-72. [PMID: 14692494 DOI: 10.1016/s0928-4257(03)00002-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The brown ghost (Apteronotus leptorhynchus) is a weakly electric gymnotiform fish that produces wave-like electric organ discharges distinguished by their enormous degree of regularity. Transient modulations of these discharges occur both spontaneously and when stimulating the fish with external electric signals that mimic encounters with a neighboring fish. Two prominent forms of modulations are chirps and gradual frequency rises. Chirps are complex frequency and amplitude modulations lasting between 20 ms and more than 200 ms. Based on their biophysical characteristics, they can be divided into four distinct categories. Gradual frequency rises consist of a rise in discharge frequency, followed by a slow return to baseline frequency. Although the modulatory phase may vary considerably between a few 100 ms and almost 100 s, there is no evidence for the existence of distinct categories of this type of modulation signal. Stimulation of the fish with external electric signals results almost exclusively in the generation of type-2 chirps. This effect is independent of the chirp type generated by the respective individual under non-evoked conditions. By contrast, no proper stimulation condition is known to evoke the other three types of chirps or gradual frequency rises in non-breeding fish. In contrast to the type-2 chirps evoked when subjecting the fish to external electric stimulation, the rate of spontaneously produced chirps is quite low. However, their rate appears to be optimized according to the probability of encountering a conspecific. As a result, the rate of non-evoked chirping is increased during the night when the fish exhibit high locomotor activity and in the time period following external electric stimulation. These, as well as other, observations demonstrate that both the type and rate of modulatory behavior are affected by a variety of behavioral conditions. This diversity at the behavioral level correlates with, and is likely to be causally linked to, the diversity of inputs received by the neurons that control chirps and gradual frequency rises, respectively. These neurons form two distinct sub-nuclei within the central posterior/prepacemaker nucleus in the dorsal thalamus. In vitro tract-tracing experiments have elucidated some of the connections of this complex with other brain regions. Direct input is received from the optic tectum. Indirect input arising from telencephalic and hypothalamic regions, as well as from the preoptic area, is relayed to the central posterior/prepacemaker nucleus via the preglomerular nucleus. Feedback loops may be provided by projections of the central posterior/prepacemaker nucleus to the preglomerular nucleus and the nucleus preopticus periventricularis.
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Affiliation(s)
- Günther K H Zupanc
- School of Biological Sciences, University of Manchester, 3.614 Stopford Building, Oxford Road, Manchester M13 9PT, UK.
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Abstract
Weakly electric fish use their electric fields to locate objects and communicate with each other. Their electric discharges vary with species, gender, and social status. This variation is mediated by steroid and peptide hormones that influence ion currents through changes in gene expression or phosphorylation state. Understanding how electric fish decode the perturbations of their electric fields that result from interactions with the discharges of other fish or prey is illuminating general mechanisms of neuronal processing. Their central sensory circuits are specialized to process amplitude modulated signals, to detect microsecond variations in spike timing, and are dynamically reconfigured depending on the stimulus parameters.
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Affiliation(s)
- Harold H Zakon
- The Section of Neurobiology, Patterson laboratory, The University of Texas, Austin, TX 78712, USA.
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Traub RD, Michelson-Law H, Bibbig AEJ, Buhl EH, Whittington MA. Gap Junctions, Fast Oscillations and the Initiation of Seizures. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 548:110-22. [PMID: 15250590 DOI: 10.1007/978-1-4757-6376-8_9] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Roger D Traub
- Department of Pshysiology, SUNY Downstate Medical Center, Brooklyn, New York, USA
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Abstract
Changes in the amplitudes of signals conveyed at synaptic contacts between neurons underlie many brain functions and pathologies. Here we review the possible determinants of the amplitude and plasticity of the elementary postsynaptic signal, the miniature. In the absence of a definite understanding of the molecular mechanism releasing transmitters, we investigated a possible alternative interpretation. Classically, both the quantal theory and the vesicle theory predict that the amount of transmitter producing a miniature is determined presynaptically prior to release and that rapid changes in miniature amplitude reflect essentially postsynaptic alterations. However, recent data indicates that short-term and long-lasting changes in miniature amplitude are in large part due to changes in the amount of transmitter in individual released packets that show no evidence of preformation. Current representations of transmitter release derive from basic properties of neuromuscular transmission and endocrine secretion. Reexamination of overlooked properties of these two systems indicate that the amplitude of miniatures may depend as much, if not more, on the Ca(2+) signals in the presynaptic terminal than on the number of postsynaptic receptors available or on vesicle's contents. Rapid recycling of transmitter and its possible adsorption at plasma and vesicle lumenal membrane surfaces suggest that exocytosis may reflect membrane traffic rather than actual transmitter release. This led us to reconsider the disregarded hypothesis introduced by Fatt and Katz (1952; J Physiol 117:109-128) that the excitability of the release site may account for the "quantal effect" in fast synaptic transmission. In this case, changes in excitability of release sites would contribute to the presynaptic quantal plasticity that is often recorded.
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Affiliation(s)
- Jean Vautrin
- Laboratory of Neurophysiology, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland 20892, USA.
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Traub RD, Pais I, Bibbig A, LeBeau FEN, Buhl EH, Hormuzdi SG, Monyer H, Whittington MA. Contrasting roles of axonal (pyramidal cell) and dendritic (interneuron) electrical coupling in the generation of neuronal network oscillations. Proc Natl Acad Sci U S A 2003; 100:1370-4. [PMID: 12525690 PMCID: PMC298779 DOI: 10.1073/pnas.0337529100] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2002] [Accepted: 12/10/2002] [Indexed: 11/18/2022] Open
Abstract
Electrical coupling between pyramidal cell axons, and between interneuron dendrites, have both been described in the hippocampus. What are the functional roles of the two types of coupling? Interneuron gap junctions enhance synchrony of gamma oscillations (25-70 Hz) in isolated interneuron networks and also in networks containing both interneurons and principal cells, as shown in mice with a knockout of the neuronal (primarily interneuronal) connexin36. We have recently shown that pharmacological gap junction blockade abolishes kainate-induced gamma oscillations in connexin36 knockout mice; without such gap junction blockade, gamma oscillations do occur in the knockout mice, albeit at reduced power compared with wild-type mice. As interneuronal dendritic electrical coupling is almost absent in the knockout mice, these pharmacological data indicate a role of axonal electrical coupling in generating the gamma oscillations. We construct a network model of an experimental gamma oscillation, known to be regulated by both types of electrical coupling. In our model, axonal electrical coupling is required for the gamma oscillation to occur at all; interneuron dendritic gap junctions exert a modulatory effect.
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Affiliation(s)
- Roger D Traub
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Box 31, Brooklyn, NY 11203, USA.
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The long-term resetting of a brainstem pacemaker nucleus by synaptic input: a model for sensorimotor adaptation. J Neurosci 2002. [PMID: 12223583 DOI: 10.1523/jneurosci.22-18-08287.2002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The cellular mechanisms behind sensorimotor adaptations, such as the adaptation to a sustained change in visual inputs by prism goggles in humans, are not known. Here we present a novel example of long-term sensorimotor adaptation in a well known neuroethological model, the jamming-avoidance response of a weakly electric fish. The adaptation is relatively long lasting, up to 9 hr in vivo, and is likely to be mediated by NMDA receptors. We demonstrate in a brain slice preparation that the pacemaker nucleus is the locus of adaptation and that it responds to long-lasting synaptic stimulation with an increase in the postsynaptic spike frequency persisting for hours after stimulus termination. The mechanism for the neuronal memory behaves as an integrator, and memory duration and strength are quantitatively related to the estimated amount of synaptic stimulation. This finding is contrary to the idea that neurons respond solely to long-lasting synaptic input by turning down their intrinsic excitability. We show that this positive feedback at the cellular level actually contributes to a negative feedback loop at the organismic level if the entire neural circuit and the behavioral link are considered.
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Light–dark-controlled changes in modulations of the electric organ discharge in the teleost Apteronotus leptorhynchus. Anim Behav 2001. [DOI: 10.1006/anbe.2001.1867] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Perez Velazquez JL, Carlen PL, Skinner FK. Artificial electrotonic coupling affects neuronal firing patterns depending upon cellular characteristics. Neuroscience 2001; 103:841-9. [PMID: 11274798 DOI: 10.1016/s0306-4522(01)00019-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
While there have been numerous theoretical studies indicating that electrotonic coupling via gap junctions interacts with the intrinsic characteristics of the coupled neurons to modify their electrical behaviour, little experimental evidence has been provided in coupled mammalian neurons. Using an artificial electrotonic junction, two distant uncoupled neurons were coupled through the computer, and the coupling conductance was varied. Tonically firing CA1 hippocampal pyramidal neurons reduced their spike firing frequency when coupled to thalamic or pyramidal cells, showing that the electrical coupling can be considered as a low-pass filter. The strength of coupling needed to entrain spike bursts of pyramidal neurons was considerably lower than the coupling needed to synchronize two neurons with different cellular characteristics (thalamic and pyramidal cells). Coupling promoted burst firing in a non-bursting cell if it was coupled to a spontaneously bursting neuron. These results support modelling studies that indicate a role for gap-junctional coupling in the synchronization of neuronal firing and the expression of low-frequency bursting.
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Affiliation(s)
- J L Perez Velazquez
- Toronto Western Research Institute, University Health Network, McL12-413, Toronto Western Hospital, 399 Bathurst Street, Toronto, Ontario M5T 2S8, Canada.
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Peinado A. Immature neocortical neurons exist as extensive syncitial networks linked by dendrodendritic electrical connections. J Neurophysiol 2001; 85:620-9. [PMID: 11160498 DOI: 10.1152/jn.2001.85.2.620] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The properties of immature cortex that may enable it to exhibit large-scale wavelike activity during a brief critical developmental period were investigated by imaging neuronal calcium signals in neonatal cortical slices under conditions of artificially enhanced excitability, conditions that produce a more frequent and robust version of the naturally occurring waves. Using pharmacological manipulation to probe the underlying mechanisms, I show that waves can propagate effectively when excitatory synaptic transmission is blocked. In contrast, propagation is very sensitive to reductions in gap junctional communication. In the barrel field cortex wave propagation is affected by the underlying cytoarchitecture in a way that is consistent with a role for dendrodendritic gap junctions. The ability of cortex to sustain wave activity ends around postnatal day 12, precisely when a major reduction in neuronal gap junctions takes place in cortex. These results suggest that in immature cortex gap junctions link neurons into extensive networks that may allow electrical activity to spread over long distances.
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Affiliation(s)
- A Peinado
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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Abstract
We analyze the existence and stability of phase-locked states of neurons coupled electrically with gap junctions. We show that spike shape and size, along with driving current (which affects network frequency), play a large role in which phase-locked modes exist and are stable. Our theory makes predictions about biophysical models using spikes of different shapes, and we present simulations to confirm the predictions. We also analyze a large system of all-to-all coupled neurons and show that the splay-phase state can exist only for a certain range of frequencies.
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Affiliation(s)
- C C Chow
- Department of Mathematics, University of Pittsburgh, PA 15206, USA
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Moortgat KT, Bullock TH, Sejnowski TJ. Gap junction effects on precision and frequency of a model pacemaker network. J Neurophysiol 2000; 83:984-97. [PMID: 10669510 DOI: 10.1152/jn.2000.83.2.984] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the precision of spike timing in a model of gap junction-coupled oscillatory neurons. The model incorporated the known physiology, morphology, and connectivity of the weakly electric fish's high-frequency and extremely precise pacemaker nucleus (Pn). Two neuron classes, pacemaker and relay cells, were each modeled with two compartments containing Hodgkin-Huxley sodium and potassium currents. Isolated pacemaker cells fired periodically, due to a constant current injection; relay cells were silent but slightly depolarized at rest. When coupled by gap junctions to other neurons, a model neuron, like its biological correlate, spiked at frequencies and amplitudes that were largely independent of current injections. The phase distribution in the network was labile to intracellular current injections and to gap junction conductance changes. The model predicts a biologically plausible gap junction conductance of 4-5 nS (200-250 MOmega). This results in a coupling coefficient of approximately 0.02, as observed in vitro. Network parameters were varied to test which could improve the temporal precision of oscillations. Increased gap junction conductances and larger numbers of cells (holding total junctional conductance per cell constant) both substantially reduced the coefficient of variation (CV = standard deviation/mean) of relay cell spike times by 74-85% and more, and did so with lower gap junction conductance when cells were contacted axonically compared with somatically. Pacemaker cell CV was only reduced when the probability of contact was increased, and then only moderately: a fivefold increase in the probability of contact reduced CV by 35%. We conclude that gap junctions facilitate synchronization, can reduce CV, are most effective between axons, and that pacemaker cells must have low intrinsic CV to account for the low CV of cells in the biological network.
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Affiliation(s)
- K T Moortgat
- Howard Hughes Medical Institute, Computational Neurobiology Laboratory, The Salk Institute, University of California, San Diego, La Jolla, California 92093, USA
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