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Powell A, Hanna C, Sajjad M, Yao R, Blum K, Gold MS, Quattrin T, Thanos PK. Exercise Influences the Brain's Metabolic Response to Chronic Cocaine Exposure in Male Rats. J Pers Med 2024; 14:500. [PMID: 38793082 PMCID: PMC11122626 DOI: 10.3390/jpm14050500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 04/30/2024] [Accepted: 04/30/2024] [Indexed: 05/26/2024] Open
Abstract
Cocaine use is associated with negative health outcomes: cocaine use disorders, speedballing, and overdose deaths. Currently, treatments for cocaine use disorders and overdose are non-existent when compared to opioid use disorders, and current standard cocaine use disorder treatments have high dropout and recidivism rates. Physical exercise has been shown to attenuate addiction behavior as well as modulate brain activity. This study examined the differential effects of chronic cocaine use between exercised and sedentary rats. The effects of exercise on brain glucose metabolism (BGluM) following chronic cocaine exposure were assessed using Positron Emission Tomography (PET) and [18F]-Fluorodeoxyglucose (FDG). Compared to sedentary animals, exercise decreased metabolism in the SIBF primary somatosensory cortex. Activation occurred in the amygdalopiriform and piriform cortex, trigeminothalamic tract, rhinal and perirhinal cortex, and visual cortex. BGluM changes may help ameliorate various aspects of cocaine abuse and reinstatement. Further investigation is needed into the underlying neuronal circuits involved in BGluM changes and their association with addiction behaviors.
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Affiliation(s)
- Aidan Powell
- Behavioral Neuropharmacology and Neuroimaging Laboratory on Addictions, Department of Pharmacology and Toxicology, Clinical Research Institute on Addictions, Jacobs School of Medicine and Biomedical Science, State University of New York at Buffalo, Buffalo, NY 14203, USA; (A.P.); (C.H.)
| | - Colin Hanna
- Behavioral Neuropharmacology and Neuroimaging Laboratory on Addictions, Department of Pharmacology and Toxicology, Clinical Research Institute on Addictions, Jacobs School of Medicine and Biomedical Science, State University of New York at Buffalo, Buffalo, NY 14203, USA; (A.P.); (C.H.)
| | - Munawwar Sajjad
- Department of Nuclear Medicine, University at Buffalo, Buffalo, NY 14214, USA; (M.S.); (R.Y.)
| | - Rutao Yao
- Department of Nuclear Medicine, University at Buffalo, Buffalo, NY 14214, USA; (M.S.); (R.Y.)
| | - Kenneth Blum
- Center for Sports, Exercise, and Mental Health, Western University of Health Sciences, Pomona, CA 91766, USA;
- Department of Molecular Biology, Adelson School of Medicine, Ariel University, Ariel 40700, Israel
| | - Mark S. Gold
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA;
| | - Teresa Quattrin
- UBMD Pediatrics, JR Oishei Children’s Hospital, University at Buffalo, Buffalo, NY 14203, USA;
| | - Panayotis K. Thanos
- Behavioral Neuropharmacology and Neuroimaging Laboratory on Addictions, Department of Pharmacology and Toxicology, Clinical Research Institute on Addictions, Jacobs School of Medicine and Biomedical Science, State University of New York at Buffalo, Buffalo, NY 14203, USA; (A.P.); (C.H.)
- Department of Molecular Biology, Adelson School of Medicine, Ariel University, Ariel 40700, Israel
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Pelletier G, Aridan N, Fellows LK, Schonberg T. A Preferential Role for Ventromedial Prefrontal Cortex in Assessing "the Value of the Whole" in Multiattribute Object Evaluation. J Neurosci 2021; 41:5056-5068. [PMID: 33906899 PMCID: PMC8197643 DOI: 10.1523/jneurosci.0241-21.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/22/2021] [Accepted: 04/18/2021] [Indexed: 11/21/2022] Open
Abstract
Everyday decision-making commonly involves assigning values to complex objects with multiple value-relevant attributes. Drawing on object recognition theories, we hypothesized two routes to multiattribute evaluation: assessing the value of the whole object based on holistic attribute configuration or summing individual attribute values. In two samples of healthy human male and female participants undergoing eye tracking and functional magnetic resonance imaging (fMRI) while evaluating novel pseudo objects, we found evidence for both forms of evaluation. Fixations to and transitions between attributes differed systematically when the value of pseudo objects was associated with individual attributes or attribute configurations. Ventromedial prefrontal cortex (vmPFC) and perirhinal cortex were engaged when configural processing was required. These results converge with our recent findings that individuals with vmPFC lesions were impaired in decisions requiring configural evaluation but not when evaluating the sum of the parts. This suggests that multiattribute decision-making engages distinct evaluation mechanisms relying on partially dissociable neural substrates, depending on the relationship between attributes and value.SIGNIFICANCE STATEMENT Decision neuroscience has only recently begun to address how multiple choice-relevant attributes are brought together during evaluation and choice among complex options. Object recognition research makes a crucial distinction between individual attribute and holistic/configural object processing, but how the brain evaluates attributes and whole objects remains unclear. Using fMRI and eye tracking, we found that the vmPFC and the perirhinal cortex contribute to value estimation specifically when value was related to whole objects, that is, predicted by the unique configuration of attributes and not when value was predicted by the sum of individual attribute values. This perspective on the interactions between subjective value and object processing mechanisms provides a novel bridge between the study of object recognition and reward-guided decision-making.
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Affiliation(s)
- Gabriel Pelletier
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Nadav Aridan
- Department of Neurobiology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Lesley K Fellows
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Tom Schonberg
- Department of Neurobiology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 6997801, Israel
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Kaskan PM, Costa VD, Eaton HP, Zemskova JA, Mitz AR, Leopold DA, Ungerleider LG, Murray EA. Learned Value Shapes Responses to Objects in Frontal and Ventral Stream Networks in Macaque Monkeys. Cereb Cortex 2018; 27:2739-2757. [PMID: 27166166 DOI: 10.1093/cercor/bhw113] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We have an incomplete picture of how the brain links object representations to reward value, and how this information is stored and later retrieved. The orbitofrontal cortex (OFC), medial frontal cortex (MFC), and ventrolateral prefrontal cortex (VLPFC), together with the amygdala, are thought to play key roles in these processes. There is an apparent discrepancy, however, regarding frontal areas thought to encode value in macaque monkeys versus humans. To address this issue, we used fMRI in macaque monkeys to localize brain areas encoding recently learned image values. Each week, monkeys learned to associate images of novel objects with a high or low probability of water reward. Areas responding to the value of recently learned reward-predictive images included MFC area 10 m/32, VLPFC area 12, and inferior temporal visual cortex (IT). The amygdala and OFC, each thought to be involved in value encoding, showed little such effect. Instead, these 2 areas primarily responded to visual stimulation and reward receipt, respectively. Strong image value encoding in monkey MFC compared with OFC is surprising, but agrees with results from human imaging studies. Our findings demonstrate the importance of VLPFC, MFC, and IT in representing the values of recently learned visual images.
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Affiliation(s)
- Peter M Kaskan
- Section on Neurobiology of Learning and Memory, Laboratory of Neuropsychology
| | - Vincent D Costa
- Unit on Learning and Decision Making, Laboratory of Neuropsychology
| | - Hana P Eaton
- Section on Neurobiology of Learning and Memory, Laboratory of Neuropsychology
| | - Julie A Zemskova
- Section on Neurobiology of Learning and Memory, Laboratory of Neuropsychology
| | | | - David A Leopold
- Section on Cognitive Neurophysiology and Imaging, Laboratory of Neuropsychology and
| | - Leslie G Ungerleider
- Section on Neurocircuitry, Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Elisabeth A Murray
- Section on Neurobiology of Learning and Memory, Laboratory of Neuropsychology
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Sasikumar D, Emeric E, Stuphorn V, Connor CE. First-Pass Processing of Value Cues in the Ventral Visual Pathway. Curr Biol 2018; 28:538-548.e3. [PMID: 29429619 PMCID: PMC5958621 DOI: 10.1016/j.cub.2018.01.051] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Revised: 11/11/2017] [Accepted: 01/15/2018] [Indexed: 11/17/2022]
Abstract
Real-world value often depends on subtle, continuously variable visual cues specific to particular object categories, like the tailoring of a suit, the condition of an automobile, or the construction of a house. Here, we used microelectrode recording in behaving monkeys to test two possible mechanisms for category-specific value-cue processing: (1) previous findings suggest that prefrontal cortex (PFC) identifies object categories, and based on category identity, PFC could use top-down attentional modulation to enhance visual processing of category-specific value cues, providing signals to PFC for calculating value, and (2) a faster mechanism would be first-pass visual processing of category-specific value cues, immediately providing the necessary visual information to PFC. This, however, would require learned mechanisms for processing the appropriate cues in a given object category. To test these hypotheses, we trained monkeys to discriminate value in four letter-like stimulus categories. Each category had a different, continuously variable shape cue that signified value (liquid reward amount) as well as other cues that were irrelevant. Monkeys chose between stimuli of different reward values. Consistent with the first-pass hypothesis, we found early signals for category-specific value cues in area TE (the final stage in monkey ventral visual pathway) beginning 81 ms after stimulus onset-essentially at the start of TE responses. Task-related activity emerged in lateral PFC approximately 40 ms later and consisted mainly of category-invariant value tuning. Our results show that, for familiar, behaviorally relevant object categories, high-level ventral pathway cortex can implement rapid, first-pass processing of category-specific value cues.
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Affiliation(s)
- Dennis Sasikumar
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Erik Emeric
- Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Veit Stuphorn
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Charles E Connor
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
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Temporal-prefrontal cortical network for discrimination of valuable objects in long-term memory. Proc Natl Acad Sci U S A 2018; 115:E2135-E2144. [PMID: 29437980 DOI: 10.1073/pnas.1707695115] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Remembering and discriminating objects based on their previously learned values are essential for goal-directed behaviors. While the cerebral cortex is known to contribute to object recognition, surprisingly little is known about its role in retaining long-term object-value associations. To address this question, we trained macaques to arbitrarily associate small or large rewards with many random fractal objects (>100) and then used fMRI to study the long-term retention of value-based response selectivity across the brain. We found a pronounced long-term value memory in core subregions of temporal and prefrontal cortex where, several months after training, fractals previously associated with high reward ("good" stimuli) elicited elevated fMRI responses compared with those associated with low reward ("bad" stimuli). Similar long-term value-based modulation was also observed in subregions of the striatum, amygdala, and claustrum, but not in the hippocampus. The value-modulated temporal-prefrontal subregions showed strong resting-state functional connectivity to each other. Moreover, for areas outside this core, the magnitude of long-term value responses was predicted by the strength of resting-state functional connectivity to the core subregions. In separate testing, free-viewing gaze behavior indicated that the monkeys retained stable long-term memory of object value. These results suggest an implicit and high-capacity memory mechanism in the temporal-prefrontal circuitry and its associated subcortical regions for long-term retention of object-value memories that can guide value-oriented behavior.
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Abstract
In 1998 several groups reported the feasibility of fMRI experiments in monkeys, with the goal to bridge the gap between invasive nonhuman primate studies and human functional imaging. These studies yielded critical insights in the neuronal underpinnings of the BOLD signal. Furthermore, the technology has been successful in guiding electrophysiological recordings and identifying focal perturbation targets. Finally, invaluable information was obtained concerning human brain evolution. We here provide a comprehensive overview of awake monkey fMRI studies mainly confined to the visual system. We review the latest insights about the topographic organization of monkey visual cortex and discuss the spatial relationships between retinotopy and category- and feature-selective clusters. We briefly discuss the functional layout of parietal and frontal cortex and continue with a summary of some fascinating functional and effective connectivity studies. Finally, we review recent comparative fMRI experiments and speculate about the future of nonhuman primate imaging.
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Affiliation(s)
- Wim Vanduffel
- Laboratory for Neuro- and Psychophysiology, KU Leuven Medical School, Campus Gasthuisberg, Leuven, 3000, Belgium; Department of Radiology, Harvard Medical School, Boston, MA 02129, USA; A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA.
| | - Qi Zhu
- Laboratory for Neuro- and Psychophysiology, KU Leuven Medical School, Campus Gasthuisberg, Leuven, 3000, Belgium
| | - Guy A Orban
- Laboratory for Neuro- and Psychophysiology, KU Leuven Medical School, Campus Gasthuisberg, Leuven, 3000, Belgium; Department of Neuroscience, University of Parma, Parma, 43125, Italy
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Mandeville JB, Liu CH, Vanduffel W, Marota JJA, Jenkins BG. Data collection and analysis strategies for phMRI. Neuropharmacology 2014; 84:65-78. [PMID: 24613447 PMCID: PMC4058391 DOI: 10.1016/j.neuropharm.2014.02.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 02/07/2014] [Accepted: 02/25/2014] [Indexed: 12/24/2022]
Abstract
Although functional MRI traditionally has been applied mainly to study changes in task-induced brain function, evolving acquisition methodologies and improved knowledge of signal mechanisms have increased the utility of this method for studying responses to pharmacological stimuli, a technique often dubbed "phMRI". The proliferation of higher magnetic field strengths and the use of exogenous contrast agent have boosted detection power, a critical factor for successful phMRI due to the restricted ability to average multiple stimuli within subjects. Receptor-based models of neurovascular coupling, including explicit pharmacological models incorporating receptor densities and affinities and data-driven models that incorporate weak biophysical constraints, have demonstrated compelling descriptions of phMRI signal induced by dopaminergic stimuli. This report describes phMRI acquisition and analysis methodologies, with an emphasis on data-driven analyses. As an example application, statistically efficient data-driven regressors were used to describe the biphasic response to the mu-opioid agonist remifentanil, and antagonism using dopaminergic and GABAergic ligands revealed modulation of the mesolimbic pathway. Results illustrate the power of phMRI as well as our incomplete understanding of mechanisms underlying the signal. Future directions are discussed for phMRI acquisitions in human studies, for evolving analysis methodologies, and for interpretative studies using the new generation of simultaneous PET/MRI scanners. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.
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Affiliation(s)
- Joseph B Mandeville
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA.
| | - Christina H Liu
- National Institute of Biomedical Imaging and Bioengineering, Bethesda, MD 20817, USA
| | - Wim Vanduffel
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - John J A Marota
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Bruce G Jenkins
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA
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Jordan CJ, Harvey RC, Baskin BB, Dwoskin LP, Kantak KM. Cocaine-seeking behavior in a genetic model of attention-deficit/hyperactivity disorder following adolescent methylphenidate or atomoxetine treatments. Drug Alcohol Depend 2014; 140:25-32. [PMID: 24811203 PMCID: PMC4075321 DOI: 10.1016/j.drugalcdep.2014.04.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 04/15/2014] [Accepted: 04/15/2014] [Indexed: 11/28/2022]
Abstract
BACKGROUND Attention-deficit/hyperactivity disorder (ADHD) is often comorbid with cocaine abuse. Controversy exists regarding long-term consequences of ADHD medications on cocaine abuse liability. Whereas childhood methylphenidate treatment may be preventative, methylphenidate in teens appears to further increase later cocaine abuse risk. In rodents, adolescent methylphenidate treatment further increases adult cocaine self-administration in the Spontaneously Hypertensive Rat (SHR) model of ADHD, whereas adolescent atomoxetine treatment does not. Effects of ADHD medications on cocaine cue reactivity, a critical component of addiction, are unknown. METHODS To investigate this, SHR, Wistar-Kyoto (inbred control) and Wistar (outbred control) rats received therapeutically relevant doses of methylphenidate (1.5 mg/kg, oral) and atomoxetine (0.3 mg/kg, intraperitoneal), or respective vehicles from post-natal day 28-55. Cocaine seeking, reflecting cue reactivity, was measured in adulthood during self-administration maintenance and cue-induced reinstatement tests conducted under a second-order schedule. RESULTS Compared to control strains, SHR earned more cocaine infusions, emitted more cocaine-seeking responses during maintenance and reinstatement testing, and required more sessions to reach the extinction criterion. Compared to vehicle, adolescent methylphenidate, but not atomoxetine, further increased cocaine intake during maintenance testing in SHR. Adolescent atomoxetine, but not methylphenidate, decreased cocaine seeking during reinstatement testing in SHR. Neither medication had effects on cocaine intake or cue reactivity in control strains. CONCLUSIONS The SHR successfully model ADHD and cocaine abuse comorbidity and show differential effects of adolescent ADHD medications on cocaine intake and cue reactivity during adulthood. Thus, SHR have heuristic value for assessing neurobiology underlying the ADHD phenotype and for evaluating pharmacotherapeutics for ADHD.
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Affiliation(s)
- Chloe J. Jordan
- Department of Psychological and Brain Sciences, Boston University, Boston, Massachusetts 02215, USA
| | - Roxann C. Harvey
- Department of Psychological and Brain Sciences, Boston University, Boston, Massachusetts 02215, USA
| | - Britahny B. Baskin
- Department of Psychological and Brain Sciences, Boston University, Boston, Massachusetts 02215, USA
| | - Linda P. Dwoskin
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Kathleen M. Kantak
- Department of Psychological and Brain Sciences, Boston University, Boston, Massachusetts 02215, USA
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Arsenault JT, Nelissen K, Jarraya B, Vanduffel W. Dopaminergic reward signals selectively decrease fMRI activity in primate visual cortex. Neuron 2013; 77:1174-86. [PMID: 23522051 DOI: 10.1016/j.neuron.2013.01.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2013] [Indexed: 10/27/2022]
Abstract
Stimulus-reward coupling without attention can induce highly specific perceptual learning effects, suggesting that reward triggers selective plasticity within visual cortex. Additionally, dopamine-releasing events-temporally surrounding stimulus-reward associations-selectively enhance memory. These forms of plasticity may be evoked by selective modulation of stimulus representations during dopamine-inducing events. However, it remains to be shown whether dopaminergic signals can selectively modulate visual cortical activity. We measured fMRI activity in monkey visual cortex during reward-only trials apart from intermixed cue-reward trials. Reward without visual stimulation selectively decreased fMRI activity within the cue representations that had been paired with reward during other trials. Behavioral tests indicated that these same uncued reward trials strengthened cue-reward associations. Furthermore, such spatially-specific activity modulations depended on prediction error, as shown by manipulations of reward magnitude, cue-reward probability, cue-reward familiarity, and dopamine signaling. This cue-selective negative reward signal offers a mechanism for selectively gating sensory cortical plasticity.
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Affiliation(s)
- John T Arsenault
- Laboratory of Neuro and Psychophysiology, KU Leuven Medical School, Campus Gasthuisberg, 3000 Leuven, Belgium
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A receptor-based model for dopamine-induced fMRI signal. Neuroimage 2013; 75:46-57. [PMID: 23466936 DOI: 10.1016/j.neuroimage.2013.02.036] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 02/11/2013] [Accepted: 02/20/2013] [Indexed: 01/22/2023] Open
Abstract
This report describes a multi-receptor physiological model of the fMRI temporal response and signal magnitude evoked by drugs that elevate synaptic dopamine in basal ganglia. The model is formulated as a summation of dopamine's effects at D1-like and D2-like receptor families, which produce functional excitation and inhibition, respectively, as measured by molecular indicators like adenylate cyclase or neuroimaging techniques like fMRI. Functional effects within the model are described in terms of relative changes in receptor occupancies scaled by receptor densities and neuro-vascular coupling constants. Using literature parameters, the model reconciles many discrepant observations and interpretations of pre-clinical data. Additionally, we present data showing that amphetamine stimulation produces fMRI inhibition at low doses and a biphasic response at higher doses in the basal ganglia of non-human primates (NHP), in agreement with model predictions based upon the respective levels of evoked dopamine. Because information about dopamine release is required to inform the fMRI model, we simultaneously acquired PET (11)C-raclopride data in several studies to evaluate the relationship between raclopride displacement and assumptions about dopamine release. At high levels of dopamine release, results suggest that refinements of the model will be required to consistently describe the PET and fMRI data. Overall, the remarkable success of the model in describing a wide range of preclinical fMRI data indicate that this approach will be useful for guiding the design and analysis of basic science and clinical investigations and for interpreting the functional consequences of dopaminergic stimulation in normal subjects and in populations with dopaminergic neuroadaptations.
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