151
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Tost H, Alam T, Meyer-Lindenberg A. Dopamine and psychosis: theory, pathomechanisms and intermediate phenotypes. Neurosci Biobehav Rev 2009; 34:689-700. [PMID: 19559045 DOI: 10.1016/j.neubiorev.2009.06.005] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 04/03/2009] [Accepted: 06/16/2009] [Indexed: 02/07/2023]
Abstract
Schizophrenia is a chronic, severe, and disabling brain disorder arising from the adverse interaction of predisposing risk genes and environmental factors. The psychopathology is characterized by a wide array of disturbing cognitive, emotional, and behavioral symptoms that interfere with the individual's capacity to function in society. Contemporary pathophysiological models assume that psychotic symptoms are triggered by a dysregulation of dopaminergic activity in the brain, a theory that is tightly linked to the serendipitous discovery of the first effective antipsychotic agents in the early 1950s. In recent years, the availability of modern neuroimaging techniques has significantly expanded our understanding of the key mediator circuits that bridge the gap between genetic susceptibility and clinical phenotype. This paper discusses the pathophysiological concepts, molecular mechanisms and neuroimaging evidence that link psychosis to disturbances in dopamine neurotransmission.
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Affiliation(s)
- Heike Tost
- Unit for Systems Neuroscience in Psychiatry, National Institute of Mental Health, NIH, DHHS, 9000 Rockville Pike, Bethesda, MD 20892-1365, USA
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152
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Associative learning and the genetics of schizophrenia. Trends Neurosci 2009; 32:359-65. [DOI: 10.1016/j.tins.2009.01.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Revised: 01/19/2009] [Accepted: 01/20/2009] [Indexed: 02/05/2023]
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153
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Patients with schizophrenia have a reduced neural response to both unpredictable and predictable primary reinforcers. Neuropsychopharmacology 2009; 34:1567-77. [PMID: 19052540 PMCID: PMC3744058 DOI: 10.1038/npp.2008.214] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
One prevalent theory of learning states that dopamine neurons signal mismatches between expected and actual outcomes, called temporal difference errors (TDEs). Evidence indicates that dopamine system dysfunction is involved in negative symptoms of schizophrenia (SZ), including avolition and anhedonia. As such, we predicted that brain responses to TDEs in dopamine midbrain nuclei and target areas would be abnormal in SZ. A total of 18 clinically stable patients with chronic SZ and 18 controls participated in an fMRI study, which used a passive conditioning task. In the task, the delivery of a small amount of juice followed a light stimulus by exactly 6 s on approximately 75% of 78 total trials, and was further delayed by 4-7 s on the remaining trials. The delayed juice delivery was designed to elicit the two types of TDE signals, associated with the recognition that a reward was omitted at the expected time, and delivered at an unexpected time. Main effects of TDE valence and group differences in the positive-negative TDE contrast (unexpected juice deliveries-juice omissions) were assessed through whole-brain and regions of interest (ROI) analyses. Main effects of TDE valence were observed for the entire sample in the midbrain, left putamen, left cerebellum, and primary gustatory cortex, bilaterally. Whole-brain analyses revealed group differences in the positive-negative TDE contrast in the right putamen and left precentral gyrus, whereas ROI analyses revealed additional group differences in the midbrain, insula, and parietal operculum, on the right, the putamen and cerebellum, on the left, and the frontal operculum, bilaterally. Further, these group differences were generally driven by attenuated responses in patients to positive TDEs (unexpected juice deliveries), whereas responses to negative TDEs (unexpected juice omissions) were largely intact. Patients also showed reductions in responses to juice deliveries on standard trials, and more blunted reinforcer responses in the left putamen corresponded to higher ratings of avolition. These results provide evidence that SZ patients show abnormal brain responses associated with the processing of a primary reinforcer, which may be a source of motivational deficits.
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154
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Stephan KE, Friston KJ, Frith CD. Dysconnection in schizophrenia: from abnormal synaptic plasticity to failures of self-monitoring. Schizophr Bull 2009; 35:509-27. [PMID: 19155345 PMCID: PMC2669579 DOI: 10.1093/schbul/sbn176] [Citation(s) in RCA: 814] [Impact Index Per Article: 54.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the last 2 decades, a large number of neurophysiological and neuroimaging studies of patients with schizophrenia have furnished in vivo evidence for dysconnectivity, ie, abnormal functional integration of brain processes. While the evidence for dysconnectivity in schizophrenia is strong, its etiology, pathophysiological mechanisms, and significance for clinical symptoms are unclear. First, dysconnectivity could result from aberrant wiring of connections during development, from aberrant synaptic plasticity, or from both. Second, it is not clear how schizophrenic symptoms can be understood mechanistically as a consequence of dysconnectivity. Third, if dysconnectivity is the primary pathophysiology, and not just an epiphenomenon, then it should provide a mechanistic explanation for known empirical facts about schizophrenia. This article addresses these 3 issues in the framework of the dysconnection hypothesis. This theory postulates that the core pathology in schizophrenia resides in aberrant N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic plasticity due to abnormal regulation of NMDARs by neuromodulatory transmitters like dopamine, serotonin, or acetylcholine. We argue that this neurobiological mechanism can explain failures of self-monitoring, leading to a mechanistic explanation for first-rank symptoms as pathognomonic features of schizophrenia, and may provide a basis for future diagnostic classifications with physiologically defined patient subgroups. Finally, we test the explanatory power of our theory against a list of empirical facts about schizophrenia.
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Affiliation(s)
- Klaas E. Stephan
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, 12 Queen Square, London WC1N 3BG, UK,Laboratory for Social and Neural Systems Research, Institute for Empirical Research in Economics, University of Zurich, Zurich, Switzerland,To whom correspondence should be addressed; tel: +44-207-8337472, fax: +44-207-8131420, e-mail:
| | - Karl J. Friston
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, 12 Queen Square, London WC1N 3BG, UK
| | - Chris D. Frith
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, 12 Queen Square, London WC1N 3BG, UK,Centre of Functionally Integrative Neuroscience (CFIN), Aarhus University Hospital, 8000-Aarhus, Denmark
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155
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Holt DJ, Lebron-Milad K, Milad MR, Rauch SL, Pitman RK, Orr SP, Cassidy BS, Walsh JP, Goff DC. Extinction memory is impaired in schizophrenia. Biol Psychiatry 2009; 65:455-63. [PMID: 18986648 PMCID: PMC3740529 DOI: 10.1016/j.biopsych.2008.09.017] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Revised: 08/20/2008] [Accepted: 09/18/2008] [Indexed: 11/18/2022]
Abstract
BACKGROUND Schizophrenia is associated with abnormalities in emotional processing and social cognition, which might result from disruption of the underlying neural mechanism(s) governing emotional learning and memory. To investigate this possibility, we measured the acquisition and extinction of conditioned fear responses and delayed recall of extinction in schizophrenia and control subjects. METHODS Twenty-eight schizophrenia and 18 demographically matched control subjects underwent a 2-day fear conditioning, extinction learning, and extinction recall procedure, in which skin conductance response (SCR) magnitude was used as the index of conditioned responses. RESULTS During fear acquisition, 83% of the control subjects and 57% of the patients showed autonomic responsivity ("responders"), and the patients showed larger SCRs to the stimulus that was not paired with the unconditioned stimulus (CS-) than the control subjects. Within the responder group, there was no difference between the patients and control subjects in levels of extinction learning; however, the schizophrenia patients showed significant impairment, relative to the control subjects, in context-dependent recall of the extinction memory. In addition, delusion severity in the patients correlated with baseline skin conductance levels. CONCLUSIONS These data are consistent with prior evidence for a heightened neural response to innocuous stimuli in schizophrenia and elevated arousal levels in psychosis. The finding of deficient extinction recall in schizophrenia patients who showed intact extinction learning suggests that schizophrenia is associated with a disturbance in the neural processes supporting emotional memory.
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Affiliation(s)
- Daphne J Holt
- Psychiatric Neuroimaging Research Program, Psychiatry Department, Massachusetts General Hospital, Boston, Massachusetts 02129, USA.
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156
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Roiser JP, Stephan KE, den Ouden HEM, Barnes TRE, Friston KJ, Joyce EM. Do patients with schizophrenia exhibit aberrant salience? Psychol Med 2009; 39:199-209. [PMID: 18588739 PMCID: PMC2635536 DOI: 10.1017/s0033291708003863] [Citation(s) in RCA: 190] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 04/28/2008] [Accepted: 05/08/2008] [Indexed: 11/07/2022]
Abstract
BACKGROUND It has been suggested that some psychotic symptoms reflect 'aberrant salience', related to dysfunctional reward learning. To test this hypothesis we investigated whether patients with schizophrenia showed impaired learning of task-relevant stimulus-reinforcement associations in the presence of distracting task-irrelevant cues. METHOD We tested 20 medicated patients with schizophrenia and 17 controls on a reaction time game, the Salience Attribution Test. In this game, participants made a speeded response to earn money in the presence of conditioned stimuli (CSs). Each CS comprised two visual dimensions, colour and form. Probability of reinforcement varied over one of these dimensions (task-relevant), but not the other (task-irrelevant). Measures of adaptive and aberrant motivational salience were calculated on the basis of latency and subjective reinforcement probability rating differences over the task-relevant and task-irrelevant dimensions respectively. RESULTS Participants rated reinforcement significantly more likely and responded significantly faster on high-probability-reinforced relative to low-probability-reinforced trials, representing adaptive motivational salience. Patients exhibited reduced adaptive salience relative to controls, but the two groups did not differ in terms of aberrant salience. Patients with delusions exhibited significantly greater aberrant salience than those without delusions, and aberrant salience also correlated with negative symptoms. In the controls, aberrant salience correlated significantly with 'introvertive anhedonia' schizotypy. CONCLUSIONS These data support the hypothesis that aberrant salience is related to the presence of delusions in medicated patients with schizophrenia, but are also suggestive of a link with negative symptoms. The relationship between aberrant salience and psychotic symptoms warrants further investigation in unmedicated patients.
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Affiliation(s)
- J P Roiser
- Institute of Cognitive Neuroscience, University College London, London, UK.
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157
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Affiliation(s)
- J Jensen
- Department of Psychiatry, University of Oslo, Oslo, Norway.
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158
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Fletcher PC, Frith CD. Perceiving is believing: a Bayesian approach to explaining the positive symptoms of schizophrenia. Nat Rev Neurosci 2008; 10:48-58. [PMID: 19050712 DOI: 10.1038/nrn2536] [Citation(s) in RCA: 806] [Impact Index Per Article: 50.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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159
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van Os J, Rutten BPF, Poulton R. Gene-environment interactions in schizophrenia: review of epidemiological findings and future directions. Schizophr Bull 2008; 34:1066-82. [PMID: 18791076 PMCID: PMC2632485 DOI: 10.1093/schbul/sbn117] [Citation(s) in RCA: 408] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Concern is building about high rates of schizophrenia in large cities, and among immigrants, cannabis users, and traumatized individuals, some of which likely reflects the causal influence of environmental exposures. This, in combination with very slow progress in the area of molecular genetics, has generated interest in more complicated models of schizophrenia etiology that explicitly posit gene-environment interactions (EU-GEI. European Network of Schizophrenia Networks for the Study of Gene Environment Interactions. Schizophrenia aetiology: do gene-environment interactions hold the key? [published online ahead of print April 25, 2008] Schizophr Res; S0920-9964(08) 00170-9). Although findings of epidemiological gene-environment interaction (G x E) studies are suggestive of widespread gene-environment interactions in the etiology of schizophrenia, numerous challenges remain. For example, attempts to identify gene-environment interactions cannot be equated with molecular genetic studies with a few putative environmental variables "thrown in": G x E is a multidisciplinary exercise involving epidemiology, psychology, psychiatry, neuroscience, neuroimaging, pharmacology, biostatistics, and genetics. Epidemiological G x E studies using indirect measures of genetic risk in genetically sensitive designs have the advantage that they are able to model the net, albeit nonspecific, genetic load. In studies using direct molecular measures of genetic variation, a hypothesis-driven approach postulating synergistic effects between genes and environment impacting on a final common pathway, such as "sensitization" of mesolimbic dopamine neurotransmission, while simplistic, may provide initial focus and protection against the numerous false-positive and false-negative results that these investigations engender. Experimental ecogenetic approaches with randomized assignment may help to overcome some of the limitations of observational studies and allow for the additional elucidation of underlying mechanisms using a combination of functional enviromics and functional genomics.
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Affiliation(s)
- Jim van Os
- Department of Psychiatry and Neuropsychology, School of Mental Health and Neuroscience, Maastricht University Medical Centre, EURON, SEARCH, Maastricht, The Netherlands.
| | - Bart PF Rutten
- Department of Psychiatry and Neuropsychology, School of Mental Health and Neuroscience, Maastricht University Medical Centre, EURON, SEARCH, PO Box 616 (location DOT 10), Maastricht, 6200 MD, The Netherlands
| | - Richie Poulton
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin, New Zealand
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160
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Mesolimbic dopamine in desire and dread: enabling motivation to be generated by localized glutamate disruptions in nucleus accumbens. J Neurosci 2008; 28:7184-92. [PMID: 18614688 DOI: 10.1523/jneurosci.4961-07.2008] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
An important issue in affective neuroscience concerns the role of mesocorticolimbic dopamine systems in positive-valenced motivation (e.g., reward) versus negative-valenced motivation (e.g., fear). Here, we assessed whether endogenous dopamine receptor stimulation in nucleus accumbens contributes to both appetitive behavior and fearful behavior that is generated in keyboard manner by local glutamate disruptions at different sites in medial shell. 6,7-Dinitroquinoxaline-2,3(1H,4H)-dione (DNQX) microinjections (450 ng) locally disrupt glutamate signals in <4 mm(3) of nucleus accumbens, and generate either desire or fear (or both) depending on precise rostrocaudal location in medial shell. At rostral shell sites, local AMPA/kainate blockade generates positive ingestive behavior, but the elicited motivated behavior becomes incrementally more fearful as the same microinjection is moved caudally. A dopamine-blocking mixture of D(1) and D(2) antagonists (raclopride and SCH-23390 [R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5,-tetrahydro-1H-3-benzazepine hydrochloride]) was combined here in the same microinjection with DNQX to assess the role of endogenous local dopamine in mediating the DNQX-motivated behaviors. We report that local dopamine blockade prevented DNQX microinjections from generating appetitive behavior (eating) in rostral shell, and equally prevented DNQX from generating fearful behavior (defensive treading) in caudal shell. We conclude that local dopamine is needed to enable disruptions of corticolimbic glutamate signals in shell to generate either positive incentive salience or negative fearful salience (valence depending on site and other conditions). Thus, dopamine interacts with localization of valence-biased glutamate circuits in medial shell to facilitate keyboard stimulation of both appetitive and fearful motivations.
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161
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Increased neural response related to neutral faces in individuals at risk for psychosis. Neuroimage 2008; 40:289-97. [DOI: 10.1016/j.neuroimage.2007.11.020] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 11/12/2007] [Accepted: 11/13/2007] [Indexed: 11/21/2022] Open
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