Dernière mise à jour de la page: 3 juillet 2009

Troubles de la personnalité et neuroimagerie cérébrale : exemple de la psychopathie

Dr Fabrice Jollant

Psychiatre

Praticien Hospitalier Universitaire

CHU Montpellier

 La psychopathie concerne 1% de la population générale (Kiehl, 2006) et 15 à 20% de la population carcérale. 80 à 90% des détenus répondent aux critères de personnalité antisociale.

On distingue la personnalité antisociale - caractérisée par la présence de comportements antisociaux - de la psychopathie, entité plus homogène. Ces deux troubles de la personnalité partagent cependant des facteurs génétiques communs. Selon l’étude de Dunedin qui s’intéresse à l’interaction entre maltraitance/génétique/comportements antisociaux, le poids de l’environnement précoce est moins important que les facteurs génétiques dans la survenue de comportements antisociaux dans l’émergence de la psychopathie.

Deux dimensions sont à distinguer dans la psychopathie :

- les comportements antisociaux : maltraitances, vols, vandalisme, agressions réactives et instrumentales ;

- le déficit émotionnel et interpersonnel : narcissisme et égocentrisme, faible empathie, peu d’attachement aux autres, absence de culpabilité.

Sur le plan neuropsychologique, la psychopathie n’est pas associée à une altération du quotient intellectuel, des capacités motrices et visuospatiales, ni à des troubles mnésiques ou attentionnels.

Au niveau neurophysiologique, les jeunes adultes présentant des comportements antisociaux présentent un défaut précoce de réponse autonome (conductances cutanées), signe d’une faible réactivité émotionnelle (Raine, 1995). D’autre part, les sujets souffrant de psychopathie présentent des troubles du langage abstrait et émotionnel : difficultés dans le traitement de l’information abstraite (Kiehl, 1999), défaut de reconnaissance de la peur d’après la prosodie (Blair, 2002), incapacité à exprimer différemment des mots affectifs et neutres (Louth, 1998) mais sans différence de temps de réaction selon la valence des mots (Williamson, 1991). Cela suggère donc que les sujets psychopathes n’ont pas le même système de communication et de réception de l’information. Une étude de Marsh et Blair a mis en évidence un défaut de reconnaissance faciale de la peur chez les psychopathes comparativement à des sujets sains. Or être capable de reconnaître les émotions d’autrui permet le développement de bonnes capacités sociales. D’autre part, les sujets psychopathes ont un déficit de conditionnement aversif : face à un stimulus aversif, leur réactivité, mesurée par conductance cutanée, reste inchangée (Veit, 2002). Enfin, l’évaluation de la prise de décision montre que ces sujets font des choix risqués, c'est-à-dire entraînant une récompense immédiate mais désavantageuse à long terme (Mitchell, 2002).

Deux régions cérébrales jouent un rôle dans la physiopathologie de la psychopathie : le cortex préfrontal ventromédian et l’amygdale. On observe un défaut d’activation du cortex temporal antérieur droit lors de la présentation de mots abstraits (Kiehl, 2004) et de l’amygdale ainsi que du cortex préfrontal ventromédian durant un conditionnement aversif (Birbaumer, 2005) chez les psychopathes comparativement à des sujets sains. Le test du « dilemne du prisonnier », reflet des performances de coopération est un outil d’évaluation pour la psychopathie (Rilling, 2007). La capacité à coopérer et l’activation du cortex orbitofrontal et de l’amygdale sont négativement corrélées.

On peut donc formuler l’hypothèse que le psychopathe n’évalue pas correctement la valeur des choses. Ses choix sont guidés par les récompenses immédiates quelques soient les risques, ce qui témoigne d’un défaut d’association entre choix et punition. De même, il est incapable de reconnaître la valeur des autres et leurs souffrances, et donc les conséquences de ses propres actes. La psychopathie peut être considérée comme une maladie développementale sévère, fortement héritable. Elle repose sur une série de déficits émotionnels sous-tendus par le cortex préfrontal ventromédian et l’amygdale, compromettant les comportements sociaux et la prise de décision.

Bibliographie:

Kiehl KA, Hare RD, McDonald JJ, Brink J.

Department of Psychology, University of British Columbia, Vancouver, Canada. kiehl@cs.ubc.ca

We tested the hypothesis that psychopathy is associated with abnormal processing of semantic and affective verbal information. In Task 1, a lexical decision task, and in Task 2, a word identification task, participants responded faster to concrete than to abstract words. In Task 2, psychopaths made more errors identifying abstract words than concrete words. In Task 3, a word identification task, participants responded faster to positive than to negative words. In all three tasks, nonpsychopaths showed the expected event-related potential (ERP) differentiation between word stimuli, whereas psychopaths did not. In each task, the ERPs of the psychopaths included a large centrofrontal negative-going wave (N350); this wave was absent or very small in the nonpsychopaths. The interpretation and significance of these differences are discussed.

Blair RJ, Mitchell DG, Richell RA, Kelly S, Leonard A, Newman C, Scott SK.

Unit on Affective Cognitive Neuroscience, Mood and Anxiety Disorders Program, National Institute of Mental Health, Bethesda, Maryland; 20892-2670, USA. Cette adresse email est protégée contre les robots des spammeurs, vous devez activer Javascript pour la voir.

The processing of emotional expressions is fundamental for normal socialization and interaction. Reduced responsiveness to the expressions of sadness and fear has been implicated in the development of psychopathy (R. J. R. Blair, 1995). The current study investigates the ability of adult psychopathic individuals to process vocal affect. Psychopathic and nonpsychopathic adults, defined by the Hare Psychopathy Checklist-Revised (PCL-R; R. D. Hare, 1991), were presented with neutral words spoken with intonations conveying happiness, disgust, anger, sadness, and fear and were asked to identify the emotion of the speaker on the basis of prosody. The results indicated that psychopathic inmates were particularly impaired in the recognition of fearful vocal affect. These results are interpreted with reference to the low-fear and violence inhibition mechanism models of psychopathy.

Louth SM, Williamson S, Alpert M, Pouget ER, Hare RD.

Psychology Department, University of British Columbia, Vancouver, Canada.

A key feature of psychopathy is the ability to deceive, manipulate, and con the unwary, while seeming to be perfectly sincere. Is this impression of sincerity achieved solely through body gestures and facial expression, or is there also something different about the voice quality of psychopaths? We analyzed the acoustic characteristics of speech in 20 male offenders (10 psychopaths and 10 nonpsychopaths), assessed with the Psychopathy Checklist--Revised (Hare, 1991). We used a computer program developed by Alpert, Merewether, Homel, Martz, and Lomask (1986) to measure variations in amplitude and prosody. Results indicated that psychopaths spoke more quietly than controls and did not differentiate, in voice emphasis, between neutral and affective words. These findings are consistent with the developing view that psychopaths are insensitive to the emotional connotations of language. In addition, their vocal characteristics may be part of a self-presentation mode designed to manipulate and control interpersonal interactions.

Williamson S, Harpur TJ, Hare RD.

Department of Psychology, University of British Columbia, Vancouver, Canada.

We tested the hypothesis that psychopathy is associated with abnormal processing of affective verbal material. Criminal psychopaths and nonpsychopaths, defined by the Psychopathy Checklist, performed a lexical decision task ("Is it a word or not?") while we recorded reaction time and event-related potentials in response to letter-strings consisting of affective and neutral words and pronounceable nonwords. On the assumption that they do not make efficient use of affective information, our primary prediction was that psychopaths would show less behavioral and event-related potential differentiation between affective and neutral words than would nonpsychopaths. The results were in accordance with this prediction. The lexical decisions of nonpsychopaths were significantly faster, and relevant event-related potential components were significantly larger, to affective words than to neutral words. In sharp contrast, psychopaths failed to show reaction time facilitation or larger amplitude event-related potentials to affective words. We suggest that psychopaths extract less information from affective words than do other individuals. Possible implications of these and related findings for understanding the behavior of psychopaths are discussed.

Marsh AA, Blair RJ.

National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA. Cette adresse email est protégée contre les robots des spammeurs, vous devez activer Javascript pour la voir.

Individuals with disorders marked by antisocial behavior frequently show deficits in recognizing displays of facial affect. Antisociality may be associated with specific deficits in identifying fearful expressions, which would implicate dysfunction in neural structures that subserve fearful expression processing. A meta-analysis of 20 studies was conducted to assess: (a) if antisocial populations show any consistent deficits in recognizing six emotional expressions; (b) beyond any generalized impairment, whether specific fear recognition deficits are apparent; and (c) if deficits in fear recognition are a function of task difficulty. Results show a robust link between antisocial behavior and specific deficits in recognizing fearful expressions. This impairment cannot be attributed solely to task difficulty. These results suggest dysfunction among antisocial individuals in specified neural substrates, namely the amygdala, involved in processing fearful facial affect.

Veit R, Flor H, Erb M, Hermann C, Lotze M, Grodd W, Birbaumer N.

Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Gartenstrasse 29, 72074, Tübingen, Germany.

While psychopaths (PP) lack anticipatory fear, social phobics (SP) are characterized by excessive fear. Criminal PP, SP and healthy controls (HC) participated in differential aversive delay conditioning with neutral faces as conditioned (CS) and painful pressure as unconditioned stimuli. Functional magnetic resonance imaging revealed differential activation in the limbic-prefrontal circuit (orbitofrontal cortex, insula, anterior cingulate, amygdala) in the HC. By contrast, the PP displayed brief amygdala, but no further brain activation. The SP showed increased activity to the faces in the amygdala and orbitofrontal cortex already during habituation. Thus, a hypoactive frontolimbic circuit may represent the neural correlate of psychopathic behavior, whereas an overactive frontolimbic system may underly social fear.

Mitchell DG, Colledge E, Leonard A, Blair RJ.

Institute of Cognitive Neuroscience, University College London, UK.

This study investigates the performance of psychopathic individuals on tasks believed to be sensitive to dorsolateral prefrontal and orbitofrontal cortex (OFC) functioning. Psychopathic and non-psychopathic individuals, as defined by the Hare psychopathy checklist revised (PCL-R) [Hare, The Hare psychopathy checklist revised, Toronto, Ontario: Multi-Health Systems, 1991] completed a gambling task [Cognition 50 (1994) 7] and the intradimensional/extradimensional (ID/ED) shift task [Nature 380 (1996) 69]. On the gambling task, psychopathic participants showed a global tendency to choose disadvantageously. Specifically, they showed an impaired ability to show learning over the course of the task. On the ID/ED task, the performance of psychopathic individuals was not significantly different from incarcerated controls on attentional set-shifting, but significant impairments were found on response reversal. These results are interpreted with reference to an OFC and amygdala dysfunction explanation of psychopathy.

PMID: 12207998 [PubMed - indexed for MEDLINE]

Kiehl KA, Smith AM, Mendrek A, Forster BB, Hare RD, Liddle PF.

Institute of Living, Hartford, CT 06106, USA. kent.kiehl@yale.edu

We tested the hypothesis that psychopathy is associated with abnormalities in semantic processing of linguistic information. Functional magnetic resonance imaging (fMRI) was used to elucidate and characterize the neural architecture underlying lexico-semantic processes in criminal psychopathic individuals and in a group of matched control participants. Participants performed a lexical decision task in which blocks of linguistic stimuli alternated with a resting baseline condition. In each lexical decision block, the stimuli were either concrete words and pseudowords or abstract words and pseudowords. Consistent with our hypothesis, psychopathic individuals, relative to controls, showed poorer behavioral performance for processing abstract words. Analysis of the fMRI data for both groups indicated that processing of word stimuli, compared with the resting baseline condition, was associated with neural activation in bilateral fusiform gyrus, anterior cingulate, left middle temporal gyrus, right posterior superior temporal gyrus, and left and right inferior frontal gyrus. Analyses confirmed our prediction that psychopathic individuals would fail to show the appropriate neural differentiation between abstract and concrete stimuli in the right anterior temporal gyrus and surrounding cortex. The results are consistent with other studies of semantic processing in psychopathy and support the theory that psychopathy is associated with right hemisphere abnormalities for processing conceptually abstract material.

Birbaumer N, Veit R, Lotze M, Erb M, Hermann C, Grodd W, Flor H.

Institute of Medical Psychology and Behavioral Neurobiology and Section of Experimental Resonance Imaging of the CNS, Department of Neuroradiology, University of Tübingen, Tübingen, Germany.

CONTEXT: Psychopaths belong to a larger group of persons with antisocial personality disorder and are characterized by an inability to have emotional involvement and by the repeated violation of the rights of others. It was hypothesized that this behavior might be the consequence of deficient fear conditioning. OBJECTIVE: To study the cerebral, peripheral, and subjective correlates of fear conditioning in criminal psychopaths and healthy control subjects. DESIGN: An aversive differential pavlovian delay conditioning paradigm with slides of neutral faces serving as conditioned and painful pressure as unconditioned stimuli. SETTING: The Department of Medical Psychology at the University of Tübingen, Tübingen, Germany. PARTICIPANTS: Ten male psychopaths as defined by the Hare Psychopathy Checklist-Revised and 10 age- and education-matched healthy male controls. The psychopaths were criminal offenders on bail and waiting for their trial or were on parole. The healthy controls were recruited from the community. MAIN OUTCOME MEASURES: Brain activation based on functional magnetic resonance imaging, electrodermal responses, emotional valence, arousal, and contingency ratings. RESULTS: The healthy controls showed enhanced differential activation in the limbic-prefrontal circuit (amygdala, orbitofrontal cortex, insula, and anterior cingulate) during the acquisition of fear and successful verbal and autonomic conditioning. The psychopaths displayed no significant activity in this circuit and failed to show conditioned skin conductance and emotional valence ratings, although contingency and arousal ratings were normal. CONCLUSION: This dissociation of emotional and cognitive processing may be the neural basis of the lack of anticipation of aversive events in criminal psychopaths.

Rilling JK, Glenn AL, Jairam MR, Pagnoni G, Goldsmith DR, Elfenbein HA, Lilienfeld SO.

Department of Anthropology, Emory University, Atlanta, Georgia 30322, USA. Cette adresse email est protégée contre les robots des spammeurs, vous devez activer Javascript pour la voir.

BACKGROUND: Psychopathy is a disorder involving a failure to experience many emotions that are necessary for appropriate social behavior. In this study, we probed the behavioral, emotional, and neural correlates of psychopathic traits within the context of a dyadic social interaction. METHODS: Thirty subjects were imaged with functional magnetic resonance imaging while playing an iterated Prisoner's Dilemma game with human confederates who were outside the scanner. Subjects also completed two self-report psychopathy questionnaires. RESULTS: Subjects scoring higher on psychopathy, particularly males, defected more often and were less likely to continue cooperating after establishing mutual cooperation with a partner. Further, they experienced more outcomes in which their cooperation was not reciprocated (cooperate-defect outcome). After such outcomes, subjects scoring high in psychopathy showed less amygdala activation, suggesting weaker aversive conditioning to those outcomes. Compared with low-psychopathy subjects, subjects higher in psychopathy also showed weaker activation within orbitofrontal cortex when choosing to cooperate and showed weaker activation within dorsolateral prefrontal and rostral anterior cingulate cortex when choosing to defect. CONCLUSIONS: These findings suggest that whereas subjects scoring low on psychopathy have emotional biases toward cooperation that can only be overcome with effortful cognitive control, subjects scoring high on psychopathy have an opposing bias toward defection that likewise can only be overcome with cognitive effort.