Categorical perception of familiarity: Evidence for a hyper-familiarity in schizophrenia

Shared multisensory experience affects Others' boundary: The enfacement illusion in schizophrenia

Schizophrenia has been described as a psychiatric condition characterized by deficits in one's own and others' face recognition, as well as by a disturbed sense of body-ownership. To date, no study has integrated these two lines of research with the aim of investigating Enfacement Illusion (EI) proneness in schizophrenia. To accomplish this goal, the classic EI protocol was adapted to test the potential plasticity of both Self-Other and Other-Other boundaries. Results showed that EI induced the expected malleability of Self-Other boundary among both controls and patients. Interestingly, for the first time, the present study demonstrates that also the Other-Other boundary was influenced by EI. Furthermore, comparing the two groups, the malleability of the Other-Other boundary showed an opposite modulation. These results suggest that, instead of greater Self-Other boundary plasticity, a qualitative difference can be detected between schizophrenia patients and controls in the malleability of the Other-Other boundary. The present study points out a totally new aspect about body-illusions and schizophrenia disorder, demonstrating that EI is not only confined to self-sphere but it also affects the way we discriminate others, representing a potential crucial aspect in the social domain.

Mirror self-face perception in individuals with schizophrenia: Feelings of strangeness associated with one's own image

Self-face recognition is crucial for sense of identity and for maintaining a coherent sense of self. Most of our daily life experiences with the image of our own face happen when we look at ourselves in the mirror. However, to date, mirror self-perception in schizophrenia has received little attention despite evidence that face recognition deficits and self abnormalities have been described in schizophrenia. Thus, this study aims to investigate mirror self-face perception in schizophrenia patients and its correlation with clinical symptoms. Twenty-four schizophrenia patients and twenty-five healthy controls were explicitly requested to describe their image in detail during 2min whilst looking at themselves in a mirror. Then, they were asked to report whether they experienced any self-face recognition difficulties. Results showed that schizophrenia patients reported more feelings of strangeness towards their face compared to healthy controls (U=209.5, p=0.048, r=0.28), but no statistically significant differences were found regarding misidentification (p=0.111) and failures in recognition (p=0.081). Symptoms such as hallucinations, somatic concerns and depression were also associated with self-face perception abnormalities (all p-values>0.05). Feelings of strangeness toward one's own face in schizophrenia might be part of a familiar face perception deficit or a more global self-disturbance, which is characterized by a loss of self-other boundaries and has been associated with abnormal body experiences and first rank symptoms. Regarding this last hypothesis, multisensorial integration might have an impact on the way patients perceive themselves since it has an important role in mirror self-perception.

Impact du traitement global/local des visages sur le sentiment de familiarité dans la schizophrénie

Contexte

Des troubles de la familiarité ont été décrits dans la schizophrénie . En particulier, une étude récente a montré un seuil de familiarité pour des visages plus faible chez les patients schizophrènes que chez les témoins, suggérant une hyper-familiarité chez les patients . Or, le traitement global d’un visage semble altéré dans la schizophrénie, alors que le traitement des détails serait préservé . Il a alors été suggéré que le sentiment de familiarité chez les patients serait basé sur un traitement prédominant des détails ; les sujets témoins analyseraient les deux types d’information. Les paradigmes d’inversion des visages altèrent sélectivement le traitement global d’un visage . Dans l’hypothèse où les troubles de la familiarité des visages dans la schizophrénie seraient liés à un traitement déficitaire de l’information globale, l’objectif de cette étude était de montrer un plus faible effet d’inversion des visages sur le sentiment de familiarité chez les patients que chez les témoins.

Méthode

Quinze patients schizophrènes et 15 témoins ont été inclus. Les stimuli étaient des morphes de visages familiers et inconnus présentés à l’endroit ou inversés (inversion haut-bas). Deux conditions d’inversion ont été utilisées : une inversion totale du visage et une inversion dite de Thatcher, dans laquelle l’orientation originelle des yeux et de la bouche était préservée. Une procédure en go/no-go a permis de mesurer le seuil de familiarité de chaque patient.

Résultats

Les patients et les témoins n’ont pas montré de seuils de familiarité différents. Contrairement à ce qui était attendu, l’effet d’inversion était significativement plus élevé chez les patients que chez les témoins. Néanmoins, l’illusion de Thatcher permettait d’améliorer les performances des patients.

Conclusion

Les informations globales et de détails semblent nécessaires aux patients pour traiter la familiarité d’un visage. Néanmoins, la restauration de l’information des détails seule permet partiellement d’améliorer ce jugement.