Nicolas Georgieff

Looking for the agent: an investigation into consciousness of action and self-consciousness in schizophrenic patients

The abilities to attribute an action to its proper agent and to understand its meaning when it is produced by someone else are basic aspects of human social communication. Several psychiatric syndromes, such as schizophrenia, seem to lead to a dysfunction of the awareness of ones own action as well as of recognition of actions performed by others. Such syndromes offer a framework for studying the determinants of agency, the ability to correctly attribute actions to their veridical source. Thirty normal subjects and 30 schizophrenic patients with and without hallucinations and/or delusional experiences were required to execute simple finger and wrist movements, without direct visual control of their hand. The image of either their own hand or an alien hand executing the same or a different movement was presented on a TV-screen in real time. The task for the subjects was to discriminate whether the hand presented on the screen was their own or not. Hallucinating and deluded schizophrenic patients were more impaired in discriminating their own hand from the alien one than the non-hallucinating ones, and tended to misattribute the alien hand to themselves. Results are discussed according to a model of action control. A tentative description of the mechanisms leading to action consciousness is proposed.

Confusion between silent and overt reading in schizophrenia

The present study was aimed at investigating whether schizophrenic patients are impaired in monitoring their own speech. In particular, we attempted to assess their ability to discriminate between overt and covert speech in a reading task, in order to verify whether they can correctly recollect the modality in which an internally generated action is produced. Subjects were asked to read either silently or aloud, items from a list of words. After a delay of 5 min, they were required to indicate in a new list which words had been read previously (either silently or overtly), or had never been presented during the reading task. With respect to normal controls, schizophrenic patients showed a significant bias to report that they had read aloud words which they had actually read silently, or which were absent during the reading task. The results are discussed in relation to recent neuroimaging studies on inner and overt speech in hallucinating schizophrenic patients. Our data favour the hypothesis that the inability to correctly discriminate between inner and overt speech may play a role in the onset of schizophrenic hallucinations.

Gaze direction determination in schizophrenia

It has been proposed that an impairment in gaze determination is responsible for the paranoid symptoms reported in schizophrenia. To address this, we examined the gaze discrimination system in schizophrenia. Thirty-two patients suffering from schizophrenia (20 patients with persecutory delusions and 12 patients without such delusions) were compared to 32 control subjects on two specific tasks. In the first task, the subjects had to determine whether 130 portraits were looking right or left. In the second task the subjects were asked to determine whether or not 130 portraits were looking at them. The absolute threshold of difference used to investigate the influence of instruction on gaze discrimination did not show any difference between patients with schizophrenia, whatever paranoid or not, and control subjects. Paranoid patients, as well as controls, displayed a significantly finer discrimination threshold in the right vs. left judgment than in the self vs. non-self judgment. Subjects with schizophrenia were able to discriminate gaze direction in the two tasks, but they took significantly more time in the task requiring to determine the presence or the absence of a mutual gaze contact than in the other one, whereas controls took the same duration to elicit both tasks. These data are consistent with those reporting that perceptual abilities are spared in schizophrenia while delusions are related to an impairment of a higher level of analysis.

Impairment of self-monitoring: part of the endophenotypic risk for psychosis

BACKGROUND A disorder of self-monitoring may underlie the positive symptoms of psychosis. The cognitive mechanisms associated with these symptoms may also be detectable in individuals at risk of psychosis. AIMS To investigate (a) whether patients with psychosis show impaired self-monitoring, (b) to what degree this is associated with positive symptoms, and (c) whether this is associated with liability to psychotic symptoms. METHOD The sample included: individuals with a lifetime history of non-affective psychosis (n=37), a genetically defined risk group (n=41), a psychometrically defined risk group (n=40), and control group (n=49). All participants carried out an action-recognition task. RESULTS Number of action-recognition errors was associated with psychosis risk (OR linear trend over 3 levels:1.12, 95% CI1.04-1.20) and differential error rate was associated with the degree of delusional ideation in a dose-response fashion (OR linear trend over 3 levels:1.13, 95% CI1.00-1.26). CONCLUSIONS Alterations in self-monitoring are associated with psychosis with evidence of specificity for delusional ideation. In the risk state, this is expressed more as failure to recognise self-generated actions, whereas in illness failure to recognise alien sources come to the fore.

Perceiving Goals and Actions in Individuals with Autism Spectrum Disorders

In the present study, we investigated the ability to parse familiar sequences of action into meaningful events in young individuals with autism spectrum disorders (ASDs), as compared to young individuals with typical development (TD) and young individuals with moderate mental retardation or learning disabilities (MLDs). While viewing two videotaped movies, participants were requested to detect the boundary transitions between component events at both fine and coarse levels of the action hierarchical structure. Overall, reduced accuracy for event detection was found in participants with ASDs, relative to participants with TD, at both levels of action segmentation. The performance was, however, equally diminished in participants with ASDs and MLDs under the course-grained segmentation suggesting that difficulties to detect fine-grained events in ASDs cannot be explained by a general intellectual dysfunction. Reduced accuracy for event detection was related to diminished event recall, memory for event sequence and Theory of Mind abilities. We hypothesized that difficulties with event detection result from a deficit disrupting the on-line processing of kinematic features and physical changes of dynamic human actions. An impairment at the earlier stages of the event encoding process might contribute to deficits in episodic memory and social functioning in individuals with ASDs.

Processus émotionnel dans la schizophrénie : étude de la composante d’évaluation

Resume Le premier objectif de cette etude etait de tester l’hypothese de polarite, c’est-a-dire l’hypothese selon laquelle l’evaluation des evenements positifs vs negatifs implique des mecanismes emotionnels differents. Le second objectif etait d’eclaircir un paradoxe apparent dans la litterature sur la schizophrenie : la tendance des patients schizophrenes a sous-evaluer le niveau de desagrement des stimuli negatifs suggere un trouble dans l’evaluation des evenements negatifs, alors que le fait que l’anhedonie constitue un trait clinique essentiel de la schizophrenie suggere au contraire la presence d’un trouble touchant principalement l’evaluation des evenements positifs. Les stimuli utilises dans notre etude etaient des photographies emotionnellement positives ou negatives, a caractere social ou non. Sur chaque photographie, deux bordures, pouvant etre soit identiques soit differentes, ont ete ajoutees. Dans une premiere experience, dite « implicite », il etait demande a des patients schizophrenes et a leurs temoins de decider si les bordures superieure et inferieure des photographies etaient identiques ou differentes. Dans une seconde experience, dite « explicite », il leur etait demande de juger si les photographies etaient agreables ou desagreables. Deux resultats obtenus sont en faveur de l’hypothese de polarite : 1) dans la condition d’evaluation implicite, l’effet du facteur polarite differait entre les patients et leurs temoins ; 2) dans la condition d’evaluation explicite, les patterns de reponse des patients et de leurs temoins differaient selon la polarite des stimuli non sociaux. De plus, les resultats ont mis en evidence un deficit dans le jugement hedonique de photographies negatives sociales et de photographies positives non sociales chez les patients schizophrenes, suggerant ainsi que le paradoxe apparent decrit ci-dessus s’eclaircit des lors que la composante sociale des stimuli est consideree. Les resultats obtenus suggerent que la polarite et la composante sociale des evenements evalues par les patients schizophrenes sont des parametres a considerer dans les prochaines etudes concernant les troubles affectifs dans la schizophrenie.

Event-related potentials during rule processing in schizophrenia

Several studies have shown that schizophrenia is characterized by impaired frontal lobe functions, functions that are responsible, for example, for the management of rules, strategic reasoning, and selective attention. Using event-related potentials (ERP), we assessed the brains electrical activity in a group of patients with schizophrenia (n=11) and a healthy control group (n=14) during a reaction time task requiring the use of a rule. ERP waves were compared with those elicited in a similar task based on a direct sensory association. In the control group, ERP analyses showed a negative wave moving from the posterior to the anterior regions of the scalp in a latency range of 250-400 ms. Then, the negativity remained at the frontal scalp region in a latency range of 400-800 ms. In this group, the amplitude was higher during the rule operation than during the sensory association task. In schizophrenic patients, the anteroposterior component of the negative wave was totally absent in both tasks, and we did not find a modulation of the ERP by the task. Frontal scalp negativity was observed, but its latency was longer and its amplitude lower than in the control group. We discuss these findings in terms of the frontoposterior disconnection hypothesis.