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Leavitt D, Alanazi FI, Al-Ozzi TM, Cohn M, Hodaie M, Kalia SK, Lozano AM, Milosevic L, Hutchison WD. Auditory oddball responses in the human subthalamic nucleus and substantia nigra pars reticulata. Neurobiol Dis 2024; 195:106490. [PMID: 38561111 DOI: 10.1016/j.nbd.2024.106490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 03/24/2024] [Accepted: 03/29/2024] [Indexed: 04/04/2024] Open
Abstract
The auditory oddball is a mainstay in research on attention, novelty, and sensory prediction. How this task engages subcortical structures like the subthalamic nucleus and substantia nigra pars reticulata is unclear. We administered an auditory OB task while recording single unit activity (35 units) and local field potentials (57 recordings) from the subthalamic nucleus and substantia nigra pars reticulata of 30 patients with Parkinson's disease undergoing deep brain stimulation surgery. We found tone modulated and oddball modulated units in both regions. Population activity differentiated oddball from standard trials from 200 ms to 1000 ms after the tone in both regions. In the substantia nigra, beta band activity in the local field potential was decreased following oddball tones. The oddball related activity we observe may underlie attention, sensory prediction, or surprise-induced motor suppression.
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Affiliation(s)
- Dallas Leavitt
- Institute of Biomedical Engineering, University of Toronto, Canada; University of Toronto - Max Planck Centre for Neural Science and Technology, University of Toronto, Canada; Krembil Brain Institute, University Health Network, Toronto, Canada
| | - Frhan I Alanazi
- Krembil Brain Institute, University Health Network, Toronto, Canada; Department of Physiology, University of Toronto, Canada
| | - Tameem M Al-Ozzi
- Krembil Brain Institute, University Health Network, Toronto, Canada; Department of Physiology, University of Toronto, Canada
| | - Melanie Cohn
- Krembil Brain Institute, University Health Network, Toronto, Canada
| | - Mojgan Hodaie
- Krembil Brain Institute, University Health Network, Toronto, Canada; Department of Surgery, University of Toronto, Canada; Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Canada
| | - Suneil K Kalia
- Krembil Brain Institute, University Health Network, Toronto, Canada; Department of Surgery, University of Toronto, Canada; Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Canada
| | - Andres M Lozano
- Krembil Brain Institute, University Health Network, Toronto, Canada; Department of Surgery, University of Toronto, Canada; Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Canada
| | - Luka Milosevic
- Institute of Biomedical Engineering, University of Toronto, Canada; University of Toronto - Max Planck Centre for Neural Science and Technology, University of Toronto, Canada; Krembil Brain Institute, University Health Network, Toronto, Canada; Center for Advancing Neurotechnological Innovation to Application (CRANIA), Toronto, Canada; KITE Research Institute, University Health Network, Toronto, Canada
| | - William D Hutchison
- Krembil Brain Institute, University Health Network, Toronto, Canada; Department of Physiology, University of Toronto, Canada; Department of Surgery, University of Toronto, Canada; Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Canada.
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2
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Avvisati R, Kaufmann AK, Young CJ, Portlock GE, Cancemi S, Costa RP, Magill PJ, Dodson PD. Distributional coding of associative learning in discrete populations of midbrain dopamine neurons. Cell Rep 2024; 43:114080. [PMID: 38581677 PMCID: PMC7616095 DOI: 10.1016/j.celrep.2024.114080] [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: 10/31/2023] [Revised: 02/12/2024] [Accepted: 03/24/2024] [Indexed: 04/08/2024] Open
Abstract
Midbrain dopamine neurons are thought to play key roles in learning by conveying the difference between expected and actual outcomes. Recent evidence suggests diversity in dopamine signaling, yet it remains poorly understood how heterogeneous signals might be organized to facilitate the role of downstream circuits mediating distinct aspects of behavior. Here, we investigated the organizational logic of dopaminergic signaling by recording and labeling individual midbrain dopamine neurons during associative behavior. Our findings show that reward information and behavioral parameters are not only heterogeneously encoded but also differentially distributed across populations of dopamine neurons. Retrograde tracing and fiber photometry suggest that populations of dopamine neurons projecting to different striatal regions convey distinct signals. These data, supported by computational modeling, indicate that such distributional coding can maximize dynamic range and tailor dopamine signals to facilitate specialized roles of different striatal regions.
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Affiliation(s)
- Riccardo Avvisati
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, UK; Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX1 3TH, UK
| | - Anna-Kristin Kaufmann
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX1 3TH, UK
| | - Callum J Young
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, UK; Computational Neuroscience Unit, Department of Computer Science, SCEEM, Faculty of Engineering, University of Bristol, Bristol BS8 1UB, UK
| | - Gabriella E Portlock
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - Sophie Cancemi
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
| | - Rui Ponte Costa
- Computational Neuroscience Unit, Department of Computer Science, SCEEM, Faculty of Engineering, University of Bristol, Bristol BS8 1UB, UK
| | - Peter J Magill
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX1 3TH, UK
| | - Paul D Dodson
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, UK; Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX1 3TH, UK.
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3
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Continuous cholinergic-dopaminergic updating in the nucleus accumbens underlies approaches to reward-predicting cues. Nat Commun 2022; 13:7924. [PMID: 36564387 PMCID: PMC9789106 DOI: 10.1038/s41467-022-35601-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 12/13/2022] [Indexed: 12/25/2022] Open
Abstract
The ability to learn Pavlovian associations from environmental cues predicting positive outcomes is critical for survival, motivating adaptive behaviours. This cued-motivated behaviour depends on the nucleus accumbens (NAc). NAc output activity mediated by spiny projecting neurons (SPNs) is regulated by dopamine, but also by cholinergic interneurons (CINs), which can release acetylcholine and glutamate via the activity of the vesicular acetylcholine transporter (VAChT) or the vesicular glutamate transporter (VGLUT3), respectively. Here we investigated behavioural and neurochemical changes in mice performing a touchscreen Pavlovian approach task by recording dopamine, acetylcholine, and calcium dynamics from D1- and D2-SPNs using fibre photometry in control, VAChT or VGLUT3 mutant mice to understand how these signals cooperate in the service of approach behaviours toward reward-predicting cues. We reveal that NAc acetylcholine-dopaminergic signalling is continuously updated to regulate striatal output underlying the acquisition of Pavlovian approach learning toward reward-predicting cues.
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Abstract
Addictive drugs are habit-forming. Addiction is a learned behavior; repeated exposure to addictive drugs can stamp in learning. Dopamine-depleted or dopamine-deleted animals have only unlearned reflexes; they lack learned seeking and learned avoidance. Burst-firing of dopamine neurons enables learning-long-term potentiation (LTP)-of search and avoidance responses. It sets the stage for learning that occurs between glutamatergic sensory inputs and GABAergic motor-related outputs of the striatum; this learning establishes the ability to search and avoid. Independent of burst-firing, the rate of single-spiking-or "pacemaker firing"-of dopaminergic neurons mediates motivational arousal. Motivational arousal increases during need states and its level determines the responsiveness of the animal to established predictive stimuli. Addictive drugs, while usually not serving as an external stimulus, have varying abilities to activate the dopamine system; the comparative abilities of different addictive drugs to facilitate LTP is something that might be studied in the future.
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Affiliation(s)
- Roy A Wise
- Intramural Research Program, National Institute on Drug Abuse, 250 Mason Lord Drive, Baltimore, MD, USA.
- Behavior Genetics Laboratory, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, MA, 02478, USA.
| | - Chloe J Jordan
- Division of Alcohol, Drugs and Addiction, Department of Psychiatry, Harvard Medical School, McLean Hospital, 115 Mill Street, Belmont, MA, 02478, USA
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5
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Abstract
Addiction is commonly identified with habitual nonmedical self-administration of drugs. It is usually defined by characteristics of intoxication or by characteristics of withdrawal symptoms. Such addictions can also be defined in terms of the brain mechanisms they activate; most addictive drugs cause elevations in extracellular levels of the neurotransmitter dopamine. Animals unable to synthesize or use dopamine lack the conditioned reflexes discussed by Pavlov or the appetitive behavior discussed by Craig; they have only unconditioned consummatory reflexes. Burst discharges (phasic firing) of dopamine-containing neurons are necessary to establish long-term memories associating predictive stimuli with rewards and punishers. Independent discharges of dopamine neurons (tonic or pacemaker firing) determine the motivation to respond to such cues. As a result of habitual intake of addictive drugs, dopamine receptors expressed in the brain are decreased, thereby reducing interest in activities not already stamped in by habitual rewards.
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Affiliation(s)
- Roy A Wise
- National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA; .,Behavioral Genetics Laboratory, McLean Hospital, Belmont, Massachusetts 02478, USA;
| | - Mykel A Robble
- Behavioral Genetics Laboratory, McLean Hospital, Belmont, Massachusetts 02478, USA;
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6
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Valdés-Baizabal C, Carbajal GV, Pérez-González D, Malmierca MS. Dopamine modulates subcortical responses to surprising sounds. PLoS Biol 2020; 18:e3000744. [PMID: 32559190 PMCID: PMC7329133 DOI: 10.1371/journal.pbio.3000744] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 07/01/2020] [Accepted: 06/03/2020] [Indexed: 11/19/2022] Open
Abstract
Dopamine guides behavior and learning through pleasure, according to classic understanding. Dopaminergic neurons are traditionally thought to signal positive or negative prediction errors (PEs) when reward expectations are, respectively, exceeded or not matched. These signed PEs are quite different from the unsigned PEs, which report surprise during sensory processing. But mounting theoretical accounts from the predictive processing framework postulate that dopamine, as a neuromodulator, could potentially regulate the postsynaptic gain of sensory neurons, thereby scaling unsigned PEs according to their expected precision or confidence. Despite ample modeling work, the physiological effects of dopamine on the processing of surprising sensory information are yet to be addressed experimentally. In this study, we tested how dopamine modulates midbrain processing of unexpected tones. We recorded extracellular responses from the rat inferior colliculus to oddball and cascade sequences, before, during, and after the microiontophoretic application of dopamine or eticlopride (a D2-like receptor antagonist). Results demonstrate that dopamine reduces the net neuronal responsiveness exclusively to unexpected sensory input without significantly altering the processing of expected input. We conclude that dopaminergic projections from the thalamic subparafascicular nucleus to the inferior colliculus could encode the expected precision of unsigned PEs, attenuating via D2-like receptors the postsynaptic gain of sensory inputs forwarded by the auditory midbrain neurons. This direct dopaminergic modulation of sensory PE signaling has profound implications for both the predictive coding framework and the understanding of dopamine function. Information about unexpected stimuli is encoded in the form of prediction error signals. The earliest prediction error signals identified in the auditory brain emerge subcortically in the inferior colliculus. This study reveals the essential role of dopamine in encoding the precision of prediction errors at the auditory midbrain.
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Affiliation(s)
- Catalina Valdés-Baizabal
- Cognitive and Auditory Neuroscience Laboratory (CANELAB), Institute of Neuroscience of Castilla y León (INCYL), Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
| | - Guillermo V. Carbajal
- Cognitive and Auditory Neuroscience Laboratory (CANELAB), Institute of Neuroscience of Castilla y León (INCYL), Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
| | - David Pérez-González
- Cognitive and Auditory Neuroscience Laboratory (CANELAB), Institute of Neuroscience of Castilla y León (INCYL), Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
- * E-mail: (DPG); (MSM)
| | - Manuel S. Malmierca
- Cognitive and Auditory Neuroscience Laboratory (CANELAB), Institute of Neuroscience of Castilla y León (INCYL), Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
- Department of Biology and Pathology, Faculty of Medicine, University of Salamanca, Salamanca, Spain
- * E-mail: (DPG); (MSM)
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7
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Jahn CI, Varazzani C, Sallet J, Walton ME, Bouret S. Noradrenergic But Not Dopaminergic Neurons Signal Task State Changes and Predict Reengagement After a Failure. Cereb Cortex 2020; 30:4979-4994. [PMID: 32390051 DOI: 10.1093/cercor/bhaa089] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 03/11/2020] [Accepted: 03/11/2020] [Indexed: 12/22/2022] Open
Abstract
The two catecholamines, noradrenaline and dopamine, have been shown to play comparable roles in behavior. Both noradrenergic and dopaminergic neurons respond to cues predicting reward availability and novelty. However, even though both are thought to be involved in motivating actions, their roles in motivation have seldom been directly compared. We therefore examined the activity of putative noradrenergic neurons in the locus coeruleus and putative midbrain dopaminergic neurons in monkeys cued to perform effortful actions for rewards. The activity in both regions correlated with engagement with a presented option. By contrast, only noradrenaline neurons were also (i) predictive of engagement in a subsequent trial following a failure to engage and (ii) more strongly activated in nonrepeated trials, when cues indicated a new task condition. This suggests that while both catecholaminergic neurons are involved in promoting action, noradrenergic neurons are sensitive to task state changes, and their influence on behavior extends beyond the immediately rewarded action.
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Affiliation(s)
- Caroline I Jahn
- Motivation, Brain and Behavior Team, Institut du Cerveau et de la Moelle Épinière, 75013 Paris, France.,Sorbonne Paris Cité universités, Université Paris Descartes, Frontières du Vivant, 75005 Paris, France.,Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of Oxford, Oxford OX13SR, UK
| | - Chiara Varazzani
- Motivation, Brain and Behavior Team, Institut du Cerveau et de la Moelle Épinière, 75013 Paris, France.,Sorbonne Paris Cité universités, Université Paris Descartes, Frontières du Vivant, 75005 Paris, France
| | - Jérôme Sallet
- Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of Oxford, Oxford OX13SR, UK.,Inserm, Stem Cell and Brain Research Institute U1208, Université Lyon, Université Lyon 1, 69500 Bron, France
| | - Mark E Walton
- Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of Oxford, Oxford OX13SR, UK
| | - Sébastien Bouret
- Motivation, Brain and Behavior Team, Institut du Cerveau et de la Moelle Épinière, 75013 Paris, France
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8
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Gardner MPH, Schoenbaum G, Gershman SJ. Rethinking dopamine as generalized prediction error. Proc Biol Sci 2018; 285:20181645. [PMID: 30464063 PMCID: PMC6253385 DOI: 10.1098/rspb.2018.1645] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 11/02/2018] [Indexed: 01/10/2023] Open
Abstract
Midbrain dopamine neurons are commonly thought to report a reward prediction error (RPE), as hypothesized by reinforcement learning (RL) theory. While this theory has been highly successful, several lines of evidence suggest that dopamine activity also encodes sensory prediction errors unrelated to reward. Here, we develop a new theory of dopamine function that embraces a broader conceptualization of prediction errors. By signalling errors in both sensory and reward predictions, dopamine supports a form of RL that lies between model-based and model-free algorithms. This account remains consistent with current canon regarding the correspondence between dopamine transients and RPEs, while also accounting for new data suggesting a role for these signals in phenomena such as sensory preconditioning and identity unblocking, which ostensibly draw upon knowledge beyond reward predictions.
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Affiliation(s)
- Matthew P H Gardner
- Intramural Research Program of the National Institute on Drug Abuse, NIH, Bethesda, MD, USA
| | - Geoffrey Schoenbaum
- Intramural Research Program of the National Institute on Drug Abuse, NIH, Bethesda, MD, USA
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Samuel J Gershman
- Department of Psychology and Center for Brain Science, Harvard University, Cambridge, MA, USA
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9
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Weinshenker D, Holmes PV. Regulation of neurological and neuropsychiatric phenotypes by locus coeruleus-derived galanin. Brain Res 2015; 1641:320-37. [PMID: 26607256 DOI: 10.1016/j.brainres.2015.11.025] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 10/27/2015] [Accepted: 11/12/2015] [Indexed: 12/28/2022]
Abstract
Decades of research confirm that noradrenergic locus coeruleus (LC) neurons are essential for arousal, attention, motivation, and stress responses. While most studies on LC transmission focused unsurprisingly on norepinephrine (NE), adrenergic signaling cannot account for all the consequences of LC activation. Galanin coexists with NE in the vast majority of LC neurons, yet the precise function of this neuropeptide has proved to be surprisingly elusive given our solid understanding of the LC system. To elucidate the contribution of galanin to LC physiology, here we briefly summarize the nature of stimuli that drive LC activity from a neuroanatomical perspective. We go on to describe the LC pathways in which galanin most likely exerts its effects on behavior, with a focus on addiction, depression, epilepsy, stress, and Alzheimer׳s disease. We propose a model in which LC-derived galanin has two distinct functions: as a neuromodulator, primarily acting via the galanin 1 receptor (GAL1), and as a trophic factor, primarily acting via galanin receptor 2 (GAL2). Finally, we discuss how the recent advances in neuropeptide detection, optogenetics and chemical genetics, and galanin receptor pharmacology can be harnessed to identify the roles of LC-derived galanin definitively. This article is part of a Special Issue entitled SI: Noradrenergic System.
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Affiliation(s)
- David Weinshenker
- Department of Human Genetics, Emory University School of Medicine, 615 Michael St., Whitehead 301, Atlanta, GA 30322, USA.
| | - Philip V Holmes
- Neuroscience Program, Biomedical and Health Sciences Institute and Psychology Department, University of Georgia, Athens, GA 30602, USA.
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10
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McGovern RA, Chan AK, Mikell CB, Sheehy JP, Ferrera VP, McKhann GM. Human substantia nigra neurons encode decision outcome and are modulated by categorization uncertainty in an auditory categorization task. Physiol Rep 2015; 3:3/9/e12422. [PMID: 26416969 PMCID: PMC4600370 DOI: 10.14814/phy2.12422] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The ability to categorize stimuli – predator or prey, friend or foe – is an essential feature of the decision-making process. Underlying that ability is the development of an internally generated category boundary to generate decision outcomes. While classic temporal difference reinforcement models assume midbrain dopaminergic neurons underlie the prediction error required to learn boundary location, these neurons also demonstrate a robust response to nonreward incentive stimuli. More recent models suggest that this may reflect a motivational aspect to performing a task which should be accounted for when modeling dopaminergic neuronal behavior. To clarify the role of substantia nigra dopamine neurons in uncertain perceptual decision making, we investigated their behavior using single neuron extracellular recordings in patients with Parkinson's disease undergoing deep brain stimulation. Subjects underwent a simple auditory categorical decision-making task in which they had to classify a tone as either low- or high-pitched relative to an explicit threshold tone and received feedback but no reward. We demonstrate that the activity of human SN dopaminergic neurons is predictive of perceptual categorical decision outcome and is modulated by uncertainty. Neuronal activity was highest during difficult (uncertain) decisions that resulted in correct responses and lowest during easy decisions that resulted in incorrect responses. This pattern of results is more consistent with a “motivational” role with regards to perceptual categorization and suggests that dopamine neurons are most active when critical information – as represented by uncertainty – is available for learning decision boundaries.
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Affiliation(s)
- Robert A McGovern
- Department of Neurological Surgery, New York-Presbyterian Hospital, Columbia University Medical Center, New York, New York
| | - Andrew K Chan
- Department of Neurological Surgery, New York-Presbyterian Hospital, Columbia University Medical Center, New York, New York
| | - Charles B Mikell
- Department of Neurological Surgery, New York-Presbyterian Hospital, Columbia University Medical Center, New York, New York
| | - John P Sheehy
- Department of Neurological Surgery, New York-Presbyterian Hospital, Columbia University Medical Center, New York, New York
| | | | - Guy M McKhann
- Department of Neurological Surgery, New York-Presbyterian Hospital, Columbia University Medical Center, New York, New York
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11
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Novelty processing and memory formation in Parkinson׳s disease. Neuropsychologia 2014; 62:124-36. [DOI: 10.1016/j.neuropsychologia.2014.07.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/05/2014] [Accepted: 07/16/2014] [Indexed: 01/25/2023]
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12
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Overton PG, Vautrelle N, Redgrave P. Sensory regulation of dopaminergic cell activity: Phenomenology, circuitry and function. Neuroscience 2014; 282:1-12. [PMID: 24462607 DOI: 10.1016/j.neuroscience.2014.01.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 01/13/2014] [Accepted: 01/14/2014] [Indexed: 01/11/2023]
Abstract
Dopaminergic neurons in a range of species are responsive to sensory stimuli. In the anesthetized preparation, responses to non-noxious and noxious sensory stimuli are usually tonic in nature, although long-duration changes in activity have been reported in the awake preparation as well. However, in the awake preparation, short-latency, phasic changes in activity are most common. These phasic responses can occur to unconditioned aversive and non-aversive stimuli, as well as to the stimuli which predict them. In both the anesthetized and awake preparations, not all dopaminergic neurons are responsive to sensory stimuli, however responsive neurons tend to respond to more than a single stimulus modality. Evidence suggests that short-latency sensory information is provided to dopaminergic neurons by relatively primitive subcortical structures - including the midbrain superior colliculus for vision and the mesopontine parabrachial nucleus for pain and possibly gustation. Although short-latency visual information is provided to dopaminergic neurons by the relatively primitive colliculus, dopaminergic neurons can discriminate between complex visual stimuli, an apparent paradox which can be resolved by the recently discovered route of information flow through to dopaminergic neurons from the cerebral cortex, via a relay in the colliculus. Given that projections from the cortex to the colliculus are extensive, such a relay potentially allows the activity of dopaminergic neurons to report the results of complex stimulus processing from widespread areas of the cortex. Furthermore, dopaminergic neurons could acquire their ability to reflect stimulus value by virtue of reward-related modification of sensory processing in the cortex. At the forebrain level, sensory-related changes in the tonic activity of dopaminergic neurons may regulate the impact of the cortex on forebrain structures such as the nucleus accumbens. In contrast, the short latency of the phasic responses to sensory stimuli in dopaminergic neurons, coupled with the activation of these neurons by non-rewarding stimuli, suggests that phasic responses of dopaminergic neurons may provide a signal to the forebrain which indicates that a salient event has occurred (and possibly an estimate of how salient that event is). A stimulus-related salience signal could be used by downstream systems to reinforce behavioral choices.
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Affiliation(s)
- P G Overton
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
| | - N Vautrelle
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - P Redgrave
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
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13
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Reward contexts extend dopamine signals to unrewarded stimuli. Curr Biol 2013; 24:56-62. [PMID: 24332545 PMCID: PMC3898276 DOI: 10.1016/j.cub.2013.10.061] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 10/16/2013] [Accepted: 10/23/2013] [Indexed: 11/22/2022]
Abstract
Basic tenets of sensory processing emphasize the importance of accurate identification and discrimination of environmental objects [1]. Although this principle holds also for reward, the crucial acquisition of reward for survival would be aided by the capacity to detect objects whose rewarding properties may not be immediately apparent. Animal learning theory conceptualizes how unrewarded stimuli induce behavioral reactions in rewarded contexts due to pseudoconditioning and higher-order context conditioning [2, 3, 4, 5, 6]. We hypothesized that the underlying mechanisms may involve context-sensitive reward neurons. We studied short-latency activations of dopamine neurons to unrewarded, physically salient stimuli while systematically changing reward context. Dopamine neurons showed substantial activations to unrewarded stimuli and their conditioned stimuli in highly rewarded contexts. The activations decreased and often disappeared entirely with stepwise separation from rewarded contexts. The influence of reward context suggests that dopamine neurons respond to real and potential reward. The influence of reward context is compatible with the reward nature of phasic dopamine responses. The responses may facilitate rapid, default initiation of behavioral reactions in environments usually containing reward. Agents would encounter more and miss less reward, resulting in survival advantage and enhanced evolutionary fitness. Dopamine neurons are activated by unrewarded events in rewarded contexts More rewarded contexts are associated with stronger dopamine activations The effective unrewarded events do not induce bidirectional prediction error signals Reward context-dependent signaling conceivably leads to more reward
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14
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Multiphasic temporal dynamics in responses of midbrain dopamine neurons to appetitive and aversive stimuli. J Neurosci 2013; 33:4710-25. [PMID: 23486944 DOI: 10.1523/jneurosci.3883-12.2013] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The transient response of dopamine neurons has been described as reward prediction error (RPE), with activation or suppression by events that are better or worse than expected, respectively. However, at least a minority of neurons are activated by aversive or high-intensity stimuli, casting doubt on the generality of RPE in describing the dopamine signal. To overcome limitations of previous studies, we studied neuronal responses to a wider variety of high-intensity and aversive stimuli, and we quantified and controlled aversiveness through a choice task in which macaques sacrificed juice to avoid aversive stimuli. Whereas most previous work has portrayed the RPE as a single impulse or "phase," here we demonstrate its multiphasic temporal dynamics. Aversive or high-intensity stimuli evoked a triphasic sequence of activation-suppression-activation extending over a period of 40-700 ms. The initial activation at short latencies (40-120 ms) reflected sensory intensity. The influence of motivational value became dominant between 150 and 250 ms, with activation in the case of appetitive stimuli, and suppression in the case of aversive and neutral stimuli. The previously unreported late activation appeared to be a modest "rebound" after strong suppression. Similarly, strong activation by reward was often followed by suppression. We suggest that these "rebounds" may result from overcompensation by homeostatic mechanisms in some cells. Our results are consistent with a realistic RPE, which evolves over time through a dynamic balance of excitation and inhibition.
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15
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Mirolli M, Santucci VG, Baldassarre G. Phasic dopamine as a prediction error of intrinsic and extrinsic reinforcements driving both action acquisition and reward maximization: a simulated robotic study. Neural Netw 2013; 39:40-51. [PMID: 23353115 DOI: 10.1016/j.neunet.2012.12.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 11/14/2012] [Accepted: 12/30/2012] [Indexed: 11/16/2022]
Abstract
An important issue of recent neuroscientific research is to understand the functional role of the phasic release of dopamine in the striatum, and in particular its relation to reinforcement learning. The literature is split between two alternative hypotheses: one considers phasic dopamine as a reward prediction error similar to the computational TD-error, whose function is to guide an animal to maximize future rewards; the other holds that phasic dopamine is a sensory prediction error signal that lets the animal discover and acquire novel actions. In this paper we propose an original hypothesis that integrates these two contrasting positions: according to our view phasic dopamine represents a TD-like reinforcement prediction error learning signal determined by both unexpected changes in the environment (temporary, intrinsic reinforcements) and biological rewards (permanent, extrinsic reinforcements). Accordingly, dopamine plays the functional role of driving both the discovery and acquisition of novel actions and the maximization of future rewards. To validate our hypothesis we perform a series of experiments with a simulated robotic system that has to learn different skills in order to get rewards. We compare different versions of the system in which we vary the composition of the learning signal. The results show that only the system reinforced by both extrinsic and intrinsic reinforcements is able to reach high performance in sufficiently complex conditions.
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Affiliation(s)
- Marco Mirolli
- Istituto di Scienze e Tecnologie della Cognizione (ISTC), CNR, Via San Martino della Battaglia 44, 00185, Roma, Italy.
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α6* nicotinic acetylcholine receptor expression and function in a visual salience circuit. J Neurosci 2012; 32:10226-37. [PMID: 22836257 DOI: 10.1523/jneurosci.0007-12.2012] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) containing α6 subunits are expressed in only a few brain areas, including midbrain dopamine (DA) neurons, noradrenergic neurons of the locus ceruleus, and retinal ganglion cells. To better understand the regional and subcellular expression pattern of α6-containing nAChRs, we created and studied transgenic mice expressing a variant α6 subunit with green fluorescent protein (GFP) fused in-frame in the M3-M4 intracellular loop. In α6-GFP transgenic mice, α6-dependent synaptosomal DA release and radioligand binding experiments confirmed correct expression and function in vivo. In addition to strong α6* nAChR expression in glutamatergic retinal axons, which terminate in superficial superior colliculus (sSC), we also found α6 subunit expression in a subset of GABAergic cell bodies in this brain area. In patch-clamp recordings from sSC neurons in brain slices from mice expressing hypersensitive α6* nAChRs, we confirmed functional, postsynaptic α6* nAChR expression. Further, sSC GABAergic neurons expressing α6* nAChRs exhibit a tonic conductance mediated by standing activation of hypersensitive α6* nAChRs by ACh. α6* nAChRs also appear in a subpopulation of SC neurons in output layers. Finally, selective activation of α6* nAChRs in vivo induced sSC neuronal activation as measured with c-Fos expression. Together, these results demonstrate that α6* nAChRs are uniquely situated to mediate cholinergic modulation of glutamate and GABA release in SC. The SC has emerged as a potential key brain area responsible for transmitting short-latency salience signals to thalamus and midbrain DA neurons, and these results suggest that α6* nAChRs may be important for nicotinic cholinergic sensitization of this pathway.
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Steinberg EE, Janak PH. Establishing causality for dopamine in neural function and behavior with optogenetics. Brain Res 2012; 1511:46-64. [PMID: 23031636 DOI: 10.1016/j.brainres.2012.09.036] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2012] [Revised: 09/17/2012] [Accepted: 09/21/2012] [Indexed: 12/15/2022]
Abstract
Dopamine (DA) is known to play essential roles in neural function and behavior. Accordingly, DA neurons have been the focus of intense experimental investigation that has led to many important advances in our understanding of how DA influences these processes. However, it is becoming increasingly appreciated that delineating the precise contributions of DA neurons to cellular, circuit, and systems-level phenomena will require more sophisticated control over their patterns of activity than conventional techniques can provide. Specifically, the roles played by DA neurons are likely to depend on their afferent and efferent connectivity, the timing and length of their neural activation, and the nature of the behavior under investigation. Recently developed optogenetic tools hold great promise for disentangling these complex issues. Here we discuss the use of light-sensitive microbial opsins in the context of outstanding questions in DA research. A major technical advance offered by these proteins is the ability to bidirectionally modulate DA neuron activity in in vitro and in vivo preparations on a time scale that more closely approximates those of neural, perceptual and behavioral events. In addition, continued advances in rodent genetics and viral-mediated gene delivery have contributed to the ability to selectively target DA neurons or their individual afferent and efferent connections. Further, these tools are suitable for use in experimental subjects engaged in complex behaviors. After reviewing the strengths and limitations of optogenetic methodologies, we conclude by describing early efforts in the application of this valuable new approach that demonstrate its potential to improve our understanding of the neural and behavioral functions of DA. This article is part of a Special Issue entitled Optogenetics (7th BRES).
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Affiliation(s)
- Elizabeth E Steinberg
- Ernest Gallo Clinic and Research Center, University of California, San Francisco, Emeryville, CA 94608, USA
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Bromberg-Martin ES, Matsumoto M, Hikosaka O. Dopamine in motivational control: rewarding, aversive, and alerting. Neuron 2011; 68:815-34. [PMID: 21144997 DOI: 10.1016/j.neuron.2010.11.022] [Citation(s) in RCA: 1421] [Impact Index Per Article: 109.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/29/2010] [Indexed: 01/18/2023]
Abstract
Midbrain dopamine neurons are well known for their strong responses to rewards and their critical role in positive motivation. It has become increasingly clear, however, that dopamine neurons also transmit signals related to salient but nonrewarding experiences such as aversive and alerting events. Here we review recent advances in understanding the reward and nonreward functions of dopamine. Based on this data, we propose that dopamine neurons come in multiple types that are connected with distinct brain networks and have distinct roles in motivational control. Some dopamine neurons encode motivational value, supporting brain networks for seeking, evaluation, and value learning. Others encode motivational salience, supporting brain networks for orienting, cognition, and general motivation. Both types of dopamine neurons are augmented by an alerting signal involved in rapid detection of potentially important sensory cues. We hypothesize that these dopaminergic pathways for value, salience, and alerting cooperate to support adaptive behavior.
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Affiliation(s)
- Ethan S Bromberg-Martin
- Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Schultz W. Dopamine signals for reward value and risk: basic and recent data. Behav Brain Funct 2010; 6:24. [PMID: 20416052 PMCID: PMC2876988 DOI: 10.1186/1744-9081-6-24] [Citation(s) in RCA: 411] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 04/23/2010] [Indexed: 01/20/2023] Open
Abstract
Background Previous lesion, electrical self-stimulation and drug addiction studies suggest that the midbrain dopamine systems are parts of the reward system of the brain. This review provides an updated overview about the basic signals of dopamine neurons to environmental stimuli. Methods The described experiments used standard behavioral and neurophysiological methods to record the activity of single dopamine neurons in awake monkeys during specific behavioral tasks. Results Dopamine neurons show phasic activations to external stimuli. The signal reflects reward, physical salience, risk and punishment, in descending order of fractions of responding neurons. Expected reward value is a key decision variable for economic choices. The reward response codes reward value, probability and their summed product, expected value. The neurons code reward value as it differs from prediction, thus fulfilling the basic requirement for a bidirectional prediction error teaching signal postulated by learning theory. This response is scaled in units of standard deviation. By contrast, relatively few dopamine neurons show the phasic activation following punishers and conditioned aversive stimuli, suggesting a lack of relationship of the reward response to general attention and arousal. Large proportions of dopamine neurons are also activated by intense, physically salient stimuli. This response is enhanced when the stimuli are novel; it appears to be distinct from the reward value signal. Dopamine neurons show also unspecific activations to non-rewarding stimuli that are possibly due to generalization by similar stimuli and pseudoconditioning by primary rewards. These activations are shorter than reward responses and are often followed by depression of activity. A separate, slower dopamine signal informs about risk, another important decision variable. The prediction error response occurs only with reward; it is scaled by the risk of predicted reward. Conclusions Neurophysiological studies reveal phasic dopamine signals that transmit information related predominantly but not exclusively to reward. Although not being entirely homogeneous, the dopamine signal is more restricted and stereotyped than neuronal activity in most other brain structures involved in goal directed behavior.
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Affiliation(s)
- Wolfram Schultz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, UK.
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Schultz W. Dopamine signals for reward value and risk: basic and recent data. BEHAVIORAL AND BRAIN FUNCTIONS : BBF 2010; 6:24. [PMID: 20416052 DOI: 10.1186/1744-9081-1186-1124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 04/23/2010] [Indexed: 05/27/2023]
Abstract
BACKGROUND Previous lesion, electrical self-stimulation and drug addiction studies suggest that the midbrain dopamine systems are parts of the reward system of the brain. This review provides an updated overview about the basic signals of dopamine neurons to environmental stimuli. METHODS The described experiments used standard behavioral and neurophysiological methods to record the activity of single dopamine neurons in awake monkeys during specific behavioral tasks. RESULTS Dopamine neurons show phasic activations to external stimuli. The signal reflects reward, physical salience, risk and punishment, in descending order of fractions of responding neurons. Expected reward value is a key decision variable for economic choices. The reward response codes reward value, probability and their summed product, expected value. The neurons code reward value as it differs from prediction, thus fulfilling the basic requirement for a bidirectional prediction error teaching signal postulated by learning theory. This response is scaled in units of standard deviation. By contrast, relatively few dopamine neurons show the phasic activation following punishers and conditioned aversive stimuli, suggesting a lack of relationship of the reward response to general attention and arousal. Large proportions of dopamine neurons are also activated by intense, physically salient stimuli. This response is enhanced when the stimuli are novel; it appears to be distinct from the reward value signal. Dopamine neurons show also unspecific activations to non-rewarding stimuli that are possibly due to generalization by similar stimuli and pseudoconditioning by primary rewards. These activations are shorter than reward responses and are often followed by depression of activity. A separate, slower dopamine signal informs about risk, another important decision variable. The prediction error response occurs only with reward; it is scaled by the risk of predicted reward. CONCLUSIONS Neurophysiological studies reveal phasic dopamine signals that transmit information related predominantly but not exclusively to reward. Although not being entirely homogeneous, the dopamine signal is more restricted and stereotyped than neuronal activity in most other brain structures involved in goal directed behavior.
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Affiliation(s)
- Wolfram Schultz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, UK.
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Abstract
Dopamine neurons carry phasic signals for a limited number of behavioural events. The events include, in descending order, reward, physically intense stimuli, risk and punishment. Recent neurophysiological studies have provided interesting details on these functions.
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Affiliation(s)
- Wolfram Schultz
- Department of Physiology, Development, and Neuroscience, University of Cambridge Downing Street, Cambridge, CB2 3DY UK
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Joshua M, Adler A, Bergman H. The dynamics of dopamine in control of motor behavior. Curr Opin Neurobiol 2009; 19:615-20. [DOI: 10.1016/j.conb.2009.10.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
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Belcher AM, O'Dell SJ, Marshall JF. Long-term changes in dopamine-stimulated gene expression after single-day methamphetamine exposure. Synapse 2009; 63:403-12. [PMID: 19177510 DOI: 10.1002/syn.20617] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Methamphetamine (mAMPH) is a highly addictive psychostimulant drug that injures monoaminergic neurons and results in behavioral impairments in humans and animals. Although evidence exists for changes in cortical volume, metabolism, and blood oxygenation levels in human mAMPH abusers, animal models have instead emphasized this drug's long-lasting influence on ascending monoaminergic (dopamine, serotonin) projections. The aim of this study was to investigate cortical and subcortical function in rats long after administration of a single-day mAMPH regimen known to damage monoaminergic systems, at a time point when behavioral impairments are still evident. Rats were given either saline or a neurotoxic (4 x 4 mg/kg, sc) mAMPH regimen. Five weeks later, they were given pharmacological treatments that stimulate cortical gene expression: either the dopaminergic agonist apomorphine (3 mg/kg, sc) or the muscarinic acetylcholine agonist pilocarpine (25 mg/kg, ip). Cortical and subcortical immediate early gene (IEG) responses were measured by immunocytochemical analysis of Fos or JunB, protein products of the IEGs, c-fos and junB. Compared with saline-pretreated controls, mAMPH-pretreated animals had about 50-70% fewer Fos- and JunB-immunoreactive cells in anterior cingulate, infralimbic, orbital, somatosensory, and rhinal cortices as well as caudate-putamen and nucleus accumbens, 90 min after apomorphine challenge. By contrast, mAMPH-pretreated rats had no reductions in the numbers of Fos or JunB-positive cells following pilocarpine challenge. This study demonstrates the profound and enduring effects of mAMPH administration on dopamine-stimulated cortical function in animals.
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Affiliation(s)
- Annabelle M Belcher
- Department of Neurobiology and Behavior, University of California, Irvine, California 92697, USA
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Isacson O, Kordower JH. Future of cell and gene therapies for Parkinson's disease. Ann Neurol 2009; 64 Suppl 2:S122-38. [PMID: 19127583 DOI: 10.1002/ana.21473] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The experimental field of restorative neurology continues to advance with implantation of cells or transfer of genes to treat patients with neurological disease. Both strategies have generated a consensus that demonstrates their capacity for structural and molecular brain modification in the adult brain. However, both approaches have yet to successfully address the complexities to make such novel therapeutic modalities work in the clinic. Prior experimental cell transplantation to patients with PD utilized dissected pieces of fetal midbrain tissue, containing mixtures of cells and neuronal types, as donor cells. Stem cell and progenitor cell biology provide new opportunities for selection and development of large batches of specific therapeutic cells. This may allow for cell composition analysis and dosing to optimize the benefit to an individual patient. The biotechnology used for cell and gene therapy for treatment of neurological disease may eventually be as advanced as today's pharmaceutical drug-related design processes. Current gene therapy phase 1 safety trials for PD include the delivery of a growth factor (neurturin via the glial cell line-derived neurotrophic factor receptor) and a transmitter enzyme (glutamic acid decarboxylase and aromatic acid decarboxylase). Many new insights from cell biological and molecular studies provide opportunities to selectively express or suppress factors relevant to neuroprotection and improved function of neurons involved in PD. Future gene and cell therapies are likely to coexist with classic pharmacological therapies because their use can be tailored to individual patients' underlying disease process and need for neuroprotective or restorative interventions.
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Affiliation(s)
- Ole Isacson
- Department of Neurology (Neuroscience), Center for Neuroregeneration Research and National Institute of Neurological Disorders and Stroke Udall Parkinson's Disease Research Center of Excellence, Harvard Medical School/McLean Hospital, Belmont, MA, USA
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Horvitz JC. Stimulus-response and response-outcome learning mechanisms in the striatum. Behav Brain Res 2008; 199:129-40. [PMID: 19135093 DOI: 10.1016/j.bbr.2008.12.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 12/04/2008] [Accepted: 12/08/2008] [Indexed: 10/21/2022]
Abstract
While midbrain DA neurons show phasic activations in response to both reward-predicting and salient non-reward events, activation responses to primary and conditioned rewards are sustained for several hundreds of milliseconds beyond those elicited by salient non-reward-related stimuli. The longer-duration DA reward response and corresponding elevated DA release in striatal target sites may selectively strengthen currently-active corticostriatal synapses, i.e., those associated with the successful reward-procuring behavior. This paper describes how similar models of DA-mediated plasticity of corticostriatal synapses may describe both stimulus-response and response-outcome learning. DA-mediated strengthening of corticostriatal synapses in regions of the dorsolateral striatum receiving afferents from primary sensorimotor cortex is likely to bind corticostriatal inputs representing the previously-emitted movement to striatal outputs contributing to the selection of the next movement segment in a behavioral sequence. Within the striatum, more generally, inputs from distinct regions of the frontal cortex that code independently for movement direction and reward expectation send convergent projections to striatal output cells. DA-mediated strengthening of active corticostriatal synapses promotes the future output of the striatal cell under similar input conditions. This is postulated to promote persistence of neuronal activity in the very cortical cells that drive corticostriatal input, leading to the establishment of sustained reverberatory loops that permit cortical movement-related cells to maintain activity until the appropriate time of movement initiation.
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Affiliation(s)
- Jon C Horvitz
- Program in Cognitive Neuroscience, Department of Psychology, The City College of the City University of New York, 138th Street and Convent Avenue, New York, NY 10031, United States.
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Sensory effects of intravenous cocaine on dopamine and non-dopamine ventral tegmental area neurons. Brain Res 2008; 1218:230-49. [PMID: 18514638 DOI: 10.1016/j.brainres.2008.04.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 04/08/2008] [Accepted: 04/10/2008] [Indexed: 11/20/2022]
Abstract
Intravenous (iv) cocaine mimics salient somato-sensory stimuli in their ability to induce rapid physiological effects, which appear to involve its action on peripherally located neural elements and fast neural transmission via somato-sensory pathways. To further clarify this mechanism, single-unit recording with fine glass electrodes was used in awake rats to examine responses of ventral tegmental area (VTA) neurons, both presumed dopamine (DA) and non-DA, to iv cocaine and tail-press, a typical somato-sensory stimulus. To exclude the contribution of DA mechanisms to the observed neuronal responses to sensory stimuli and cocaine, recordings were conducted during full DA receptor blockade (SCH23390+eticloptide). Iv cocaine (0.25 mg/kg delivered over 10 s) induced significant excitations of approximately 63% of long-spike (presumed DA) and approximately 70% of short-spike (presumed non-DA) VTA neurons. In both subgroups, neuronal excitations occurred with short latencies (4-8 s), peaked at 10-20 s (30-40% increase over baseline) and disappeared at 30-40 s after the injection onset. Most long-(67%) and short-spike (89%) VTA neurons also showed phasic responses to tail-press (5-s). All responsive long-spike cells were excited by tail-press; excitations were very rapid (peak at 1 s) and strong (100% rate increase over baseline) but brief (2-3 s). In contrast, both excitations (60%) and inhibitions (29%) were seen in short-spike cells. These responses were also rapid and transient, but excitations of short-spike units were more prolonged and sustained (10-15 s) than in long-spike cells. These data suggest that in awake animals iv cocaine, like somato-sensory stimuli, rapidly and transiently excites VTA neurons of different subtypes. Therefore, along with direct action on specific brain substrates, central effects of cocaine may occur, via an indirect mechanism, involving peripheral neural elements, visceral sensory nerves and rapid neural transmission. Via this mechanism, cocaine, like somato-sensory stimuli, can rapidly activate DA neurons and induce phasic DA release, creating the conditions for DA accumulation by a later occurring and prolonged direct inhibiting action on DA uptake. By providing a rapid neural signal and triggering transient neural activation, such a peripherally driven action might play a crucial role in the sensory effects of cocaine, thus contributing to learning and development of drug-taking behavior.
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Hernádi L, Vehovszky Á, Győri J, Hiripi L. Neuronal background of activation of estivated snails, with special attention to the monoaminergic system: a biochemical, physiological, and neuroanatomical study. Cell Tissue Res 2007; 331:539-53. [DOI: 10.1007/s00441-007-0522-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Accepted: 09/20/2007] [Indexed: 11/29/2022]
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Windels F, Kiyatkin EA. Dopamine action in the substantia nigra pars reticulata: iontophoretic studies in awake, unrestrained rats. Eur J Neurosci 2006; 24:1385-94. [PMID: 16987223 DOI: 10.1111/j.1460-9568.2006.05015.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Dopamine (DA) neurons located in the substantia nigra pars compacta release DA not only via axonal terminals, affecting neurotransmission within the striatum, but also via dendrites, some of which densely protrude into the substantia nigra pars reticulata (SNr). Although the interaction of dendritically released DA with somatodendritic autoreceptors regulates DA cell activity, released DA may also affect SNr neurons. These cells, however, lack postsynaptic DA receptors, making it unclear how locally released DA modulates their activity. Although previous work in brain slices suggests that DA might modulate the activity of GABA inputs, thus affecting SNr neurons indirectly, it remains unclear how increased or decreased DA release might affect these cells exposed to normal afferent inputs. To explore this issue, we examined the effects of iontophoretic DA and amphetamine on SNr neurons in awake, unrestrained rats. DA had no consistent effects on SNr cells but amphetamine, known to induce DA release, dose-dependently inhibited most of them. This effect was blocked by SCH23390, a selective D1 receptor blocker, which itself strongly increased neuronal discharge rate. As GABA input is a major factor regulating the activity of SNr neurons, our data suggest that dendritically released DA, by interacting with D1 receptors on striato-nigral and pallido-nigral afferents, is able to decrease this input, thus releasing SNr neurons from tonic, GABA-mediated inhibition. Surprisingly, a full DA receptor blockade (SCH23390 + eticlopride) did not result in the expected increase in SNr discharge rate, suggesting that other mechanisms are responsible for behavioral abnormalities following acute disruption of DA transmission.
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Affiliation(s)
- François Windels
- Cellular Neurobiology Branch, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, DHHS, 333 Cassell Drive, Baltimore, MD 21224, USA
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Kiyatkin EA, Brown PL. The role of peripheral and central sodium channels in mediating brain temperature fluctuations induced by intravenous cocaine. Brain Res 2006; 1117:38-53. [PMID: 16956595 PMCID: PMC1847334 DOI: 10.1016/j.brainres.2006.08.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 07/27/2006] [Accepted: 08/04/2006] [Indexed: 11/26/2022]
Abstract
While cocaine's interaction with the dopamine (DA) transporter and subsequent increase in DA transmission are usually considered key factors responsible for its locomotor stimulatory and reinforcing properties, many centrally mediated physiological and psychoemotional effects of cocaine are resistant to DA receptor blockade, suggesting the importance of other non-DA mechanisms. To explore the role of cocaine's interaction with Na+ channels, rats were used to compare locomotor stimulatory and temperature (NAcc, temporal muscle and skin) effects of repeated iv injections of cocaine (1 mg/kg) with those induced by procaine (PRO 5 mg/kg), a short-acting local anesthetic with negligible effect on the DA transporter, and cocaine methiodide (COC-MET 1.31 mg/kg), a quaternary cocaine derivative that is unable to cross the blood-brain barrier. While PRO, unlike cocaine, did not induce locomotor activation, it mimicked cocaine in its ability to increase brain temperature following the initial injection and to induce biphasic, down-up fluctuations following repeated injections. This similarity suggests that both these effects of cocaine may be driven by its action on Na+ channels, a common action of both drugs. While COC-MET also did not affect locomotor activity, it shared with cocaine and PRO their ability to increase brain temperature but failed to induce temperature decreases after repeated injections. These findings point toward activation of peripheral Na+ channels as the primary mechanism of rapid excitatory effects of cocaine and inhibition of centrally located Na+ channels as the primary mechanism for transient inhibitory effects of cocaine. DA receptor blockade (SCH23390+eticlopride) fully eliminated locomotor stimulatory and temperature-increasing effects of cocaine, but its temperature-decreasing effects remained intact. Surprisingly, DA receptor blockade also altered the temperature fluctuations caused by PRO and COC-MET, suggesting that some of the central effects triggered via Na+ channels are in fact DA-dependent. Finally, repeated administration of PRO to animals that had previous cocaine experience led to conditioned locomotion and potentiated temperature-increasing effects of this drug. It appears, therefore, that, in addition to the central effects of cocaine mediated via interaction with the DA transporter and potentiation of DA uptake, interaction with peripheral and central Na+ channels is important for the initial physiological and, perhaps, affective effects of cocaine, likely contributing to the unique abuse potential of this drug.
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Affiliation(s)
- Eugene A Kiyatkin
- Cellular Neurobiology Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, DHHS, 333 Cassell Drive, Baltimore, MD 21224, USA.
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Horowitz TS, Choi WY, Horvitz JC, Côté LJ, Mangels JA. Visual search deficits in Parkinson's disease are attenuated by bottom-up target salience and top-down information. Neuropsychologia 2006; 44:1962-77. [PMID: 16580700 DOI: 10.1016/j.neuropsychologia.2006.01.037] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/02/2005] [Indexed: 11/21/2022]
Abstract
Patients with Parkinson's disease (PD), a degenerative disorder primarily affecting the nigrostriatal dopamine system, exhibit deficits in selecting task-relevant stimuli in the presence of irrelevant stimuli, such as in visual search tasks. However, results from previous studies suggest that these deficits may vary as a function of whether selection must rely primarily on the "bottom-up" salience of the target relative to background stimuli, or whether "top-down" information about the identity of the target is available to bias selection. In the present study, moderate-to-severe medicated PD patients and age-matched controls were tested on six visual search tasks that systematically varied the relationship between bottom-up target salience (feature search, noisy feature search, conjunction search) and top-down target knowledge (Target Known versus Target Unknown). Comparison of slope and intercepts of the RT x set size function provided information about the efficiency of search and non-search (e.g., decision, response) components, respectively. Patients exhibited higher intercepts than controls as bottom-up target salience decreased, however these deficits were disproportionately larger under Target Unknown compared to Target Known conditions. Slope differences between PD and controls were limited to the Target Unknown Conjunction condition, where patients exhibited a shallower slope in the target absent condition, indicating that they terminated search earlier. These results suggest that under conditions of high background noise, medicated PD patients were primarily impaired in decision and/or response processes downstream from the target search itself, and that the deficit was attenuated when top-down information was available to guide selection of the target signal.
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Affiliation(s)
- Todd S Horowitz
- Brigham & Women's Hospital and Harvard Medical School, MA, USA
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Wilson DIG, Bowman EM. Neurons in dopamine-rich areas of the rat medial midbrain predominantly encode the outcome-related rather than behavioural switching properties of conditioned stimuli. Eur J Neurosci 2006; 23:205-18. [PMID: 16420430 DOI: 10.1111/j.1460-9568.2005.04535.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Midbrain dopamine neurons are phasically activated by a variety of sensory stimuli. It has been hypothesized that these activations contribute to reward prediction or behavioural switching. To test the latter hypothesis we recorded from 131 single neurons in the ventral tegmental area and retrorubral field of thirsty rats responding during a modified go/no-go task. One-quarter (n = 33) of these neurons responded to conditioned stimuli in the task, which varied according to the outcome with which they were associated (saccharin or quinine solution) and according to whether they triggered a switch in the ongoing sequence of the animal's behaviour ('behavioural switching'). Almost half the neurons (45%) responded differentially to saccharin- vs. quinine-conditioned stimuli; the activity of a minority (15%) correlated with an aspect of behavioural switching (mostly exhibiting changes from baseline activity in the absence of a behavioural switch) and one-third (33%) encoded various outcome-switch combinations. The strongest response was excitation to the saccharin-conditioned stimulus. Additionally, a proportion (38%) of neurons responded during outcome delivery, typically exhibiting inhibition during saccharin consumption. The neurons sampled did not fall into distinct clusters on the basis of their electrophysiological characteristics. However, most neurons that responded to the outcome-related properties of conditioned stimuli had long action potentials (> 1.2 ms), a reported characteristic of dopamine neurons. Moreover, responses to saccharin-conditioned stimuli were functionally akin to dopamine responses found in the macaque and rat nucleus accumbens responses observed within the same task. In conclusion, our data are more consistent with the reward-prediction than the behavioural switching hypothesis.
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Affiliation(s)
- David I G Wilson
- School of Psychology, University of St Andrews, St Mary's, Quadrangle, South Street, St Andrews, Fife, Scotland KY16 9JP, UK.
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32
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Abstract
In anesthetized animals, dopamine neurons fire in tonic and phasic firing modes hypothesized to be regulated by dissociable circuit mechanisms. Salient events critical to learning, reward processing, and attentional selection elicit transient phasic bursts. It is unclear, however, how burst activity contributes to sustained firing patterns in awake animals and if behavioral conditions known to affect dopaminergic neurotransmission change impulse activity levels. Acute stress is known to increase extracellular dopamine in the striatum and the prefrontal cortex. In this study, we have used multiunit recording to define and follow activity patterns in single dopaminergic neurons across days and to determine how restraint, a model of acute stress, changes tonic and phasic firing patterns. Long-term recording shows that a population of 23 putative dopamine neurons has heterogeneous firing profiles under baseline conditions. In all, 62% showed significant burst activity under resting conditions, while others showed predominantly regular (17%) or random (21%) activity patterns. Restraint increased mean firing rate in all dopamine neurons, but preferentially increased burst firing in neurons with higher burst rates under resting conditions. Finally, we show that increased burst firing can persist 24 h after a single exposure to stress. These data indicate that subsets of dopamine neurons may be sensitive to circuit mechanisms activated by stress and that persistent changes in burst firing may be evidence of synaptic plasticity. Furthermore, increased burst firing may be a mechanism through which stress augments extracellular dopamine in selected terminal regions.
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Affiliation(s)
- Kristin K Anstrom
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
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33
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Zink CF, Pagnoni G, Chappelow J, Martin-Skurski M, Berns GS. Human striatal activation reflects degree of stimulus saliency. Neuroimage 2005; 29:977-83. [PMID: 16153860 PMCID: PMC1819473 DOI: 10.1016/j.neuroimage.2005.08.006] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Revised: 07/26/2005] [Accepted: 08/04/2005] [Indexed: 10/25/2022] Open
Abstract
Salient stimuli are characterized by their capability to perturb and seize available cognitive resources. Although the striatum and its dopaminergic inputs respond to a variety of stimuli categorically defined as salient, including rewards, the relationship between striatal activity and saliency is not well understood. Specifically, it is unclear if the striatum responds in an all-or-none fashion to salient events or instead responds in a graded fashion to the degree of saliency associated with an event. Using functional magnetic resonance imaging, we measured activity in the brains of 20 participants performing a visual classification task in which they identified single digits as odd or even numbers. An auditory tone preceded each number, which was occasionally, and unexpectedly, substituted by a novel sound. The novel sounds varied in their ability to interrupt and reallocate cognitive resources (i.e., their saliency) as measured by a delay in reaction time to immediately subsequent numerical task-stimuli. The present findings demonstrate that striatal activity increases proportionally to the degree to which an unexpected novel sound interferes with the current cognitive focus, even in the absence of reward. These results suggest that activity in the human striatum reflects the level of saliency associated with a stimulus, perhaps providing a signal to reallocate limited resources to important events.
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Affiliation(s)
| | | | | | | | - Gregory S. Berns
- * Corresponding author. Fax: +1 404 727 3233. E-mail address: (G.S. Berns)
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34
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Rodd ZA, Anstrom KK, Knapp DJ, Racz I, Zimmer A, Serra S, Bell RL, Woodward DJ, Breese GR, Colombo G. Factors Mediating Alcohol Craving and Relapse: Stress, Compulsivity, and Genetics. Alcohol Clin Exp Res 2005; 29:1325-33. [PMID: 16088996 PMCID: PMC2874961 DOI: 10.1097/01.alc.0000171487.62079.a3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Zachary A Rodd
- Institute of Psychiatric Research, Department of Psychiatry, Indiana University School of Medicine, Indianapolis, 46202-4887, USA.
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35
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Necessary methodological and stem cell advances for restoration of the dopaminergic system in Parkinson's disease patients. NEURODEGENER DIS 2005. [DOI: 10.1017/cbo9780511544873.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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36
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Isacson O, Bjorklund LM, Schumacher JM. Toward full restoration of synaptic and terminal function of the dopaminergic system in Parkinson's disease by stem cells. Ann Neurol 2003; 53 Suppl 3:S135-46; discussion S146-8. [PMID: 12666105 DOI: 10.1002/ana.10482] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
New therapeutic nonpharmacological methodology in Parkinson's disease (PD) involves cell and synaptic renewal or replacement to restore function of neuronal systems, including the dopaminergic (DA) system. Using fetal DA cell therapy in PD patients and laboratory models, it has been demonstrated that functional motor deficits associated with parkinsonism can be reduced. Similar results have been observed in animal models with stem cell-derived DA neurons. Evidence obtained from transplanted PD patients further shows that the underlying disease process does not destroy transplanted fetal DA cells, although degeneration of the host nigrostriatal system continues. The optimal DA cell regeneration system would reconstitute a normal neuronal network capable of restoring feedback-controlled release of DA in the nigrostriatal system. The success of cell therapy for PD is limited by access to preparation and development of highly specialized dopaminergic neurons found in the A9 and A10 region of the substantia nigra pars compacta as well as the technical and surgical steps associated with the transplantation procedure. Recent laboratory work has focused on using stem cells as a starting point for deriving the optimal DA cells to restore the nigrostriatal system. Ultimately, understanding the cell biological principles necessary for generating functional DA neurons can provide many new avenues for better treatment of patients with PD.
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Affiliation(s)
- Ole Isacson
- Udall Parkinson's Disease Research Center of Excellence, McLean Hospital/Harvard Medical School, Belmont, MA 02478, USA.
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37
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Horvitz JC. Dopamine gating of glutamatergic sensorimotor and incentive motivational input signals to the striatum. Behav Brain Res 2002; 137:65-74. [PMID: 12445716 DOI: 10.1016/s0166-4328(02)00285-1] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Dopamine (DA) neurons of the substantia nigra (SN) and ventral tegmental area (VTA) respond to a wide category of salient stimuli. Activation of SN and VTA DA neurons, and consequent release of nigrostriatal and mesolimbic DA, modulates the processing of concurrent glutamate inputs to dorsal and ventral striatal target regions. According to the view described here, this occurs under conditions of unexpected environmental change regardless of whether that change is rewarding or aversive. Nigrostriatal and mesolimbic DA activity gates the input of sensory, motor, and incentive motivational (e.g. reward) signals to the striatum. In light of recent single-unit and brain imaging data, it is suggested that the striatal reward signals originate in the orbitofrontal cortex and basolateral amygdala (BLA), regions that project strongly to the striatum. A DA signal of salient unexpected event occurrence, from this framework, gates the throughput of the orbitofrontal glutamate reward input to the striatum just as it gates the throughput of corticostriatal sensory and motor signals needed for normal response execution. Processing of these incoming signals is enhanced when synaptic DA levels are high, because DA enhances the synaptic efficacy of strong concurrent glutamate inputs while reducing the efficacy of weak glutamate inputs. The impairments in motor performance and incentive motivational processes that follow from nigrostriatal and mesolimbic DA loss can be understood in terms of a single mechanism: abnormal processing of sensorimotor and incentive motivation-related glutamate input signals to the striatum.
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Affiliation(s)
- Jon C Horvitz
- Department of Psychology, Columbia University, 1190 Amsterdam Ave, Rm 406, New York, NY 10027, USA.
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38
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Garris PA, Rebec GV. Modeling fast dopamine neurotransmission in the nucleus accumbens during behavior. Behav Brain Res 2002; 137:47-63. [PMID: 12445715 DOI: 10.1016/s0166-4328(02)00284-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Recent advances in electrophysiology and voltammetry permit monitoring of dopamine (DA) neuronal activity in real time in the brain of awake animals. Studies using these approaches demonstrate that behaviorally relevant events elicit characteristic patterns of electrical activity in midbrain DA neurons as well as large, transient changes in extracellular DA in the nucleus accumbens (NAc). In addition to providing insight into the role of the DA system in the processing of motor, motivational, and sensory information, the new findings also shed light on fast DA neurotransmission in a behavioral context. This report, (1). summarizes the information obtained by electrophysiological and real-time voltammetric approaches and (2). describes a general model of phasic DA signaling in the NAc that links the observed changes in DA electrical activity and extracellular dynamics. The analysis demonstrates that the behaviorally evoked DA transients are governed by similar mechanisms as those produced by short trains of electrical stimulation. Thus, action potential-dependent release and presynaptic uptake are primary determinants of functional DA levels in the brain during behavior. Interestingly, the model predicts that the same burst of electrical activity generated at DA cell bodies produces markedly different DA dynamics in forebrain projection fields. The distinct changes result from heterogeneous release and uptake rates and may underlie region-specific effects of DA. Auto- and heteroreceptors, as well as other sites of presynaptic control, could further modulate the DA transients.
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Affiliation(s)
- Paul A Garris
- Department of Biological Sciences, Illinois State University, 244 SLB, Normal, IL 61790-4120, USA.
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39
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Levita L, Dalley JW, Robbins TW. Nucleus accumbens dopamine and learned fear revisited: a review and some new findings. Behav Brain Res 2002; 137:115-27. [PMID: 12445718 DOI: 10.1016/s0166-4328(02)00287-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A role for the nucleus accumbens (NAcc) and its dopamine (DA) innervation in fear and fear learning is supported by a large body of evidence, which has challenged the view that the NAcc is solely involved in mediating appetitive processes. Unfortunately, due to conflicting findings in the aversive conditioning literature the role of the NAcc in aversive conditioning remains unclear. This review focuses on the results of recent in vivo microdialysis studies that have examined the release of NAcc DA during Pavlovian aversive conditioning. In addition, we present additional new findings, which re-examine the involvement of NAcc DA in aversive conditioning. DA release was measured in the NAcc core using in vivo microdialysis during discrete cue Pavlovian aversive conditioning in four experiments. In all cases no change in DA levels was observed either during training or in response to the CS presentations despite robust behavioural evidence of discrete cue Pavlovian aversive conditioning. These findings contrast with some previous studies that show that primary and conditioned aversive stimuli increase DA release in the NAcc. We suggest that the inconsistencies in the literature might be due to procedural differences in the measurement of aversive conditioning, and the precise location of the probe in the NAcc region. Hence, rather than discount an involvement of NAcc DA in affective processes, we propose that functionally dissociable sub-regions of the NAcc may contribute to different aspects of Pavlovian aversive learning.
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Affiliation(s)
- Liat Levita
- Department of Experimental Psychology, University of Cambridge, Downing Street, CB2 3EB, Cambridge, UK.
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40
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Hyland BI, Reynolds JNJ, Hay J, Perk CG, Miller R. Firing modes of midbrain dopamine cells in the freely moving rat. Neuroscience 2002; 114:475-92. [PMID: 12204216 DOI: 10.1016/s0306-4522(02)00267-1] [Citation(s) in RCA: 372] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
There is a large body of data on the firing properties of dopamine cells in anaesthetised rats or rat brain slices. However, the extent to which these data relate to more natural conditions is uncertain, as there is little quantitative information available on the firing properties of these cells in freely moving rats. We examined this by recording from the midbrain dopamine cell fields using chronically implanted microwire electrodes. (1) In most cases, slowly firing cells with broad action potentials were profoundly inhibited by the dopamine agonist apomorphine, consistent with previously accepted criteria. However, a small group of cells was found that were difficult to classify because of ambiguous combinations of properties. (2) Presumed dopamine cells could be divided into low and high bursting (>40% of their spikes in bursts) groups, with the majority having low bursting rates. The distribution of burst incidence was similar to that previously reported with chloral hydrate anaesthesia, but the average intraburst frequency was higher in the conscious animal at rest and was higher again in bursts triggered by salient stimuli. (3) There was no evidence for spike frequency adaptation within bursts on average, consistent with the hypothesis that afterhyperpolarisation currents may be disabled during behaviourally induced bursting. (4) Presumed dopamine cells responded to reward-related stimuli with increased bursting rates and significantly higher intraburst frequencies compared to bursts emitted outside task context, indicating that modulation of afferent activity might not only trigger bursting, but may also regulate burst intensity. (5) In addition to the irregular single spike and bursting modes we found that extremely regular (clock-like) firing, previously only described for dopamine cells in reduced preparations, can also be expressed in the freely moving animal. (6) Cross-correlation analysis of activity recorded from simultaneously recorded neurones revealed coordinated activity in a quarter of dopamine cell pairs consistent with at least "functional" connectivity. On the other hand, most dopamine cell pairs showed no correlation, leaving open the possibility of functional sub-groupings within the dopamine cell fields. Taken together, the data suggest that the basic firing modes described for dopamine cells in reduced or anaesthetised preparations do reflect natural patterns of activity for these neurones, but also that the details of this activity are dependent upon modulation of afferent inputs by behavioural stimuli.
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Affiliation(s)
- B I Hyland
- Department of Physiology, School of Medical Sciences, University of Otago, P.O. Box 913, Dunedin, New Zealand.
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41
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Abstract
There has been a growing recognition that pulsatile stimulation of dopamine receptors may be an important mechanism in the generation of the motor fluctuations that often develop and compromise the effectiveness of long-term levodopa administration in persons with Parkinson's disease (PD). This has prompted investigation of treatment approaches that might provide more constant, and therefore physiological, dopamine receptor stimulation. Frequent levodopa administration, controlled-release levodopa preparations, inhibitors of levodopa metabolism, and duodenal, subcutaneous and even intravenous infusions of levodopa or dopamine agonists have all been employed with this goal in mind, but all have limitations. Transdermal drug delivery is a treatment approach that is not only capable of providing a constant rate of drug delivery, but is also non-invasive and relatively simple to use. However, developing a drug to be delivered transdermally for the treatment of PD has been anything but easy. Levodopa and many dopamine agonists are not sufficiently soluble to be administered via the transdermal route, and blind alleys have been encountered thus far in the investigation of suitably soluble drugs. Nevertheless, investigation continues and yet another candidate drug, rotigotine (N-0923), is currently under active investigation. Techniques designed to enhance skin permeation and thus improve the effectiveness of transdermal drug delivery are also potential sources for future treatment advances.
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Affiliation(s)
- Ronald F Pfeiffer
- Department of Neurology, University of Tennessee Health Science Center, Memphis 38163, USA.
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42
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Abstract
Dopamine projections from the midbrain to the striatum and frontal cortex are involved in behavioral reactions controlled by rewards, as inferred from deficits in parkinsonism, schizophrenia, and drug addiction. Recent experiments have shown that dopamine neurons are not directly modulated in relation to movements. Rather, they appear to code the rewarding aspects of environmental stimuli. They show short, phasic increases of activity following primary food and liquid rewards ("unconditioned stimuli") and conditioned, reward-predicting stimuli of visual, auditory, and somatosensory modalities. They also display smaller activation-depression sequences after stimuli resembling rewards and after novel or particularly intense stimuli. Rewards are only reported as far as they occur differently than predicted. According to learning theories, a "prediction error" message may constitute a powerful teaching signal for behavior and learning. The phasic reward message is different from the more tonic enabling function of dopamine that is deficient in Parkinson's disease, indicating that dopamine neurons subserve different functions at different time scales. Neurons in other brain structures, such as the striatum, orbitofrontal cortex, and amygdala, code the quality, quantity, and preference of rewards. The dopamine reward prediction error signal may cooperate with these reward perception signals during the learning and performance of behavioral reactions to motivating environmental stimuli.
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Affiliation(s)
- W Schultz
- Institute of Physiology and Program in Neuroscience, University of Fribourg, Switzerland.
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43
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Castro SL, Zigmond MJ. Stress-induced increase in extracellular dopamine in striatum: role of glutamatergic action via N-methyl-d-aspartate receptors in substantia nigra. Brain Res 2001; 901:47-54. [PMID: 11368949 DOI: 10.1016/s0006-8993(01)02229-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
There is considerable support for an influence of excitatory amino acids released from corticofugal neurons on dopaminergic activity in the basal ganglia. However, the relative importance of cortico-striatal and cortico-mesencephalic projections remains unclear, particularly with respect to the nigro-neostriatal pathway. We have therefore examined the influence of endogenous excitatory amino acids in substantia nigra on stress-induced dopaminergic activity in neostriatum. Microdialysis probes were implanted unilaterally into substantia nigra and ipsilateral neostriatum, and dopamine release in neostriatum was monitored by measuring changes in extracellular dopamine. In separate animals, neostriatal dopamine synthesis was assessed by measuring extracellular DOPA in the presence of 3-hydroxylbenzylhydrazine (NSD-1015; 100 microM), an inhibitor of aromatic amino acid decarboxylase. Thirty minutes of intermittent foot shock increased both dopamine release (+41%) and synthesis (+37%) in neostriatum. Infusion of 2-amino-5-phosphonovalerate (APV; 100 microM), an inhibitor of N-methyl-D-aspartate (NMDA) receptors, into substantia nigra greatly attenuated the stress-induced increase in neostriatal dopamine release, while having no effect on the apparent increase in stress-induced dopamine synthesis. These data suggest that excitatory amino acids such as glutamate act on NMDA receptors in substantia nigra to increase striatal dopamine release produced by exposure to stress, but that the increase in dopamine synthesis is mediated through a separate mechanism.
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Affiliation(s)
- S L Castro
- Departments of Neurology and Psychiatry, University of Pittsburgh, Pittsburgh, PA 15261, USA
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44
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Abstract
The fundamental biological importance of rewards has created an increasing interest in the neuronal processing of reward information. The suggestion that the mechanisms underlying drug addiction might involve natural reward systems has also stimulated interest. This article focuses on recent neurophysiological studies in primates that have revealed that neurons in a limited number of brain structures carry specific signals about past and future rewards. This research provides the first step towards an understanding of how rewards influence behaviour before they are received and how the brain might use reward information to control learning and goal-directed behaviour.
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Affiliation(s)
- W Schultz
- Institute of Physiology and Program in Neuroscience, University of Fribourg, CH-1700 Fribourg, Switzerland.
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45
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Nutt JG, Obeso JA, Stocchi F. Continuous dopamine-receptor stimulation in advanced Parkinson's disease. Trends Neurosci 2000; 23:S109-15. [PMID: 11052228 DOI: 10.1016/s1471-1931(00)00029-x] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Intermittent or pulsatile dopamine-receptor stimulation is postulated to induce plastic changes in motor systems that are responsible for the development of the motor fluctuations and dyskinesia that complicate long-term L-dopa therapy of Parkinson's disease. As a corollary to this hypothesis, continuous dopamine-receptor stimulation can avoid or reverse these complications. Such continuous stimulation is unlikely to mimic completely the normal function of the dopaminergic system, but should avoid the supra-physiological swings in extracellular dopamine that accompany intermittent L-dopa dosing. The concern is that this continuous stimulation might induce tolerance rather than sensitization to some effects of L-dopa. Open clinical trials support the value of continuous dopaminergic stimulation in Parkinson's disease with established motor complications, but rigorous studies, although experimentally difficult, are needed.
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Affiliation(s)
- J G Nutt
- Dept of Neurology, Oregon Health Sciences University, Portland 97201, USA
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46
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Abstract
While it has previously been assumed that mesolimbic dopamine neurons carry a reward signal, recent data from single-unit, microdialysis and voltammetry studies suggest that these neurons respond to a large category of salient and arousing events, including appetitive, aversive, high intensity, and novel stimuli. Elevations in dopamine release within mesolimbic, mesocortical and nigrostriatal target sites coincide with arousal, and the increase in dopamine activity within target sites modulates a number of behavioral functions. However, because dopamine neurons respond to a category of salient events that extend beyond that of reward stimuli, dopamine levels are not likely to code for the reward value of encountered events. The paper (i) examines evidence showing that dopamine neurons respond to salient and arousing change in environmental conditions, regardless of the motivational valence of that change, and (ii) asks how this might shape our thinking about the role of dopamine systems in goal-directed behavior.
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Affiliation(s)
- J C Horvitz
- Department of Psychology, Columbia University, New York 10027, USA.
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47
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Suri RE, Schultz W. A neural network model with dopamine-like reinforcement signal that learns a spatial delayed response task. Neuroscience 1999; 91:871-90. [PMID: 10391468 DOI: 10.1016/s0306-4522(98)00697-6] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This study investigated how the simulated response of dopamine neurons to reward-related stimuli could be used as reinforcement signal for learning a spatial delayed response task. Spatial delayed response tasks assess the functions of frontal cortex and basal ganglia in short-term memory, movement preparation and expectation of environmental events. In these tasks, a stimulus appears for a short period at a particular location, and after a delay the subject moves to the location indicated. Dopamine neurons are activated by unpredicted rewards and reward-predicting stimuli, are not influenced by fully predicted rewards, and are depressed by omitted rewards. Thus, they appear to report an error in the prediction of reward, which is the crucial reinforcement term in formal learning theories. Theoretical studies on reinforcement learning have shown that signals similar to dopamine responses can be used as effective teaching signals for learning. A neural network model implementing the temporal difference algorithm was trained to perform a simulated spatial delayed response task. The reinforcement signal was modeled according to the basic characteristics of dopamine responses to novel stimuli, primary rewards and reward-predicting stimuli. A Critic component analogous to dopamine neurons computed a temporal error in the prediction of reinforcement and emitted this signal to an Actor component which mediated the behavioral output. The spatial delayed response task was learned via two subtasks introducing spatial choices and temporal delays, in the same manner as monkeys in the laboratory. In all three tasks, the reinforcement signal of the Critic developed in a similar manner to the responses of natural dopamine neurons in comparable learning situations, and the learning curves of the Actor replicated the progress of learning observed in the animals. Several manipulations demonstrated further the efficacy of the particular characteristics of the dopamine-like reinforcement signal. Omission of reward induced a phasic reduction of the reinforcement signal at the time of the reward and led to extinction of learned actions. A reinforcement signal without prediction error resulted in impaired learning because of perseverative errors. Loss of learned behavior was seen with sustained reductions of the reinforcement signal, a situation in general comparable to the loss of dopamine innervation in Parkinsonian patients and experimentally lesioned animals. The striking similarities in teaching signals and learning behavior between the computational and biological results suggest that dopamine-like reward responses may serve as effective teaching signals for learning behavioral tasks that are typical for primate cognitive behavior, such as spatial delayed responding.
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Affiliation(s)
- R E Suri
- Institute of Physiology and Program in Neuroscience, University of Fribourg, Switzerland
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48
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Striatal neuronal activity and responsiveness to dopamine and glutamate after selective blockade of D1 and D2 dopamine receptors in freely moving rats. J Neurosci 1999. [PMID: 10212318 DOI: 10.1523/jneurosci.19-09-03594.1999] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although striatal neurons receive continuous dopamine (DA) input, little information is available on the role of such input in regulating normal striatal functions. To clarify this issue, we assessed how systemic administration of selective D1 and D2 receptor blockers or their combination alters striatal neuronal processing in freely moving rats. Single-unit recording was combined with iontophoresis to monitor basal impulse activity of dorsal and ventral striatal neurons and their responses to glutamate (GLU), a major source of excitatory striatal drive, and DA. SCH-23390 (0.2 mg/kg), a D1 antagonist, strongly elevated basal activity and attenuated neuronal responses to DA compared with control conditions, but GLU-induced excitations were enhanced relative to control as indicated by a reduction in response threshold, an increase in response magnitude, and a more frequent appearance of apparent depolarization inactivation. In contrast, the D2 antagonist eticlopride (0.2 mg/kg) had a weak depressing effect on basal activity and was completely ineffective in blocking the neuronal response to DA. Although eticlopride reduced the magnitude of the GLU response, the response threshold was lower, and depolarization inactivation occurred more often relative to control. The combined administration of these drugs resembled the effects of SCH-23390, but whereas the change in basal activity and the GLU response was weaker, the DA blocking effect was stronger than SCH-23390 alone. Our data support evidence for DA as a modulator of striatal function and suggest that under behaviorally relevant conditions tonically released DA acts mainly via D1 receptors to provide a continuous inhibiting or restraining effect on both basal activity and responsiveness of striatal neurons to GLU-mediated excitatory input.
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49
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Guarraci FA, Kapp BS. An electrophysiological characterization of ventral tegmental area dopaminergic neurons during differential pavlovian fear conditioning in the awake rabbit. Behav Brain Res 1999; 99:169-79. [PMID: 10512583 DOI: 10.1016/s0166-4328(98)00102-8] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Recent research has suggested that the mesencephalic dopaminergic (DA) system is activated by stress. For example, alterations in DA metabolites have been found in the ventral tegmental area (VTA) following footshock and immobilization in the rat [15,37]. Furthermore, this activation appears selective to DA neurons within the VTA since no changes were observed within the substantia nigra [15,16]. While this research suggests that DA neurons in the VTA are activated by aversive events, there has been a paucity of electrophysiological research designed to examine the sensory response characteristics of these DA neurons, and in particular their response to stimuli which predict aversive events. The present study was conducted to investigate the response characteristics of DA neurons within the VTA of the awake rabbit to acoustic stimuli which, via Pavlovian aversive conditioning procedures, came to predict the occurrence of a mild shock to the pinna. 45%, of the neurons meeting pre-established criteria for DA neurons demonstrated either significant excitation or inhibition to conditioned aversive stimuli. These neurons responded differentially to CS+ and CS- presentations. Some of these neurons (65%) demonstrated a greater increase in activity during the CS+ compared to the CS-, some (22%,) demonstrated a greater decrease in activity during the CS+ compared to the CS- and some (13%) demonstrated a greater increase in activity during the CS- compared to the CS+. Further, conditioned heart rate responses in the rabbits occurred during the recording of a majority of these neurons. These overall results suggest that conditioned aversive stimuli can affect the firing of VTA DA neurons and that these neurons comprise a heterogenous population with respect to their response profiles.
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Affiliation(s)
- F A Guarraci
- Department of Psychology, University of Vermont, Burlington 05405, USA.
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Kiyatkin EA, Rebec GV. Heterogeneity of ventral tegmental area neurons: single-unit recording and iontophoresis in awake, unrestrained rats. Neuroscience 1998; 85:1285-309. [PMID: 9681963 DOI: 10.1016/s0306-4522(98)00054-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Single-unit recording combined with iontophoresis of dopamine, GABA, and glutamate was used in awake, unrestrained rats to characterize the electrophysiological and receptor properties of neurons in the ventral tegmental area under naturally occurring behavioural conditions. All isolated ventral tegmental area units (n=90) were analysed and compared with cells (n=58) recorded from dorsally adjacent areas of the pre-rubral area and red nucleus. Two distinct neuronal groups were identified in the ventral tegmental area: units with triphasic, long-duration spikes (78/90) and units with biphasic, short-duration spikes (12/90). Although all long-spike units discharged in an irregular, bursting pattern with varying degrees of within-burst decrements in spike amplitude, they could be further subdivided into at least three distinct subgroups. Type I long-spike units (36/78) discharged at a relatively slow and stable rate (mean: 6.03 imp/s; range: 0.42-15.78) with no evident fluctuations during movement. These cells were inhibited by dopamine and GABA and responded to glutamate with a low-magnitude excitation accompanied by a pronounced decrement in spike amplitude and a powerful rebound inhibition. Type II long-spike units (23/78) had relatively high and unstable discharge rates (mean: 22.82 imp/s; range: 4.42-59.67) and showed movement-related phasic activations frequently followed by partial or complete cessation of firing. Some Type II cells (4/9) were inhibited by dopamine, but all were excited by glutamate at very low currents (0-10 nA). With an increase in current, the glutamate-induced excitation often (18/22) progressed into a cessation of firing. All these cells were inhibited by GABA followed by a strong rebound excitation (8/9), which also frequently (6/8) resulted in cessation of firing. Type III long-spike units (19/78) had properties that differed from either Type I or Type II cells, including a lack of spontaneous firing (5/19). Short-spike ventral tegmental area units were either silent (4/12) and unresponsive to dopamine and GABA or spontaneously active (range: 0.89-34.13 imp/s) and inhibited by GABA and, in some cases (2/8). by dopamine; all were phasically activated during movement and glutamate iontophoresis. It appears that ventral tegmental area neurons, including those with long-duration spikes, do not comprise a uniform population in awake, unrestrained rats. Type I, long-spike units match the characteristics of histochemically-identified dopamine neurons, and they appear to express dopamine autoreceptors, which may explain the relatively slow, stable rate of activity and the limited responsiveness to excitatory inputs. Although the nature of the other long-spike units in our sample is unclear, they may include dopamine neurons without autoreceptors as well as non-dopamine cells. The heterogeneity of ventral tegmental area neurons is an important consideration for further attempts to assess the role of the mesocorticolimbic dopamine system in motivated behaviour.
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Affiliation(s)
- E A Kiyatkin
- Department of Psychology, Indiana University, Bloomington 47405, USA
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