Ophélie Favrod

Rethinking Body Ownership in Schizophrenia: Experimental and Meta-analytical Approaches Show no Evidence for Deficits

Schizophrenia is a severe psychiatric disorder, in which patients experience an abnormal sense of self. While deficits in sensorimotor self-representation (agency) are well documented in schizophrenia, less is known about other aspects of bodily self-representation (body ownership). Here, we tested a large cohort (N = 59) of chronic schizophrenia patients and matched controls (N = 30) on a well-established body illusion paradigm, the Full Body Illusion (FBI). In this paradigm, changes in body ownership are induced through prolonged multisensory stimulation, in which participants are stroked on their back while seeing the stroking on the back of a virtual body. When the felt and seen stroking are synchronous, participants typically feel higher identification with the seen body as well as a drift in self-location towards it. However, when the stroking is asynchronous, no such changes occur. Our results show no evidence for abnormal body ownership in schizophrenia patients. A meta-analysis of previous work corroborates this result. Thus, while schizophrenia patients may be impaired in the sense of agency, their multisensory bodily self-representation, as tested here, seems to be unaffected by the illness.

Electrophysiological correlates of visual backward masking in high schizotypic personality traits participants

Visual backward masking is strongly deteriorated in patients with schizophrenia. Masking deficits are associated with strongly reduced amplitudes of the global field power in the EEG. Healthy participants who scored high in cognitive disorganization (a schizotypic trait) were impaired in backward masking compared to participants who scored low. Here, we show that the global field power is also reduced in healthy participants scoring high (n=25) as compared to low (n=20) in cognitive disorganization, though quantitatively less pronounced than in patients (n=10). These results point to similar mechanisms underlying visual backward masking deficits along the schizophrenia spectrum.

Pathological completion in the intact visual field of hemianopia patients

ABSTRACT We investigated figure segregation in the intact visual field (VF) of hemianopia patients. Three patients and matched controls performed a Yes–No figure detection task, where square or square fragments were embedded in a background of randomly oriented Gabor elements. We varied orientation and number of the fragment elements, stimulus eccentricity and background density (BD). Figure detection was impaired in all three patients in the entire intact VF, but potentially more pronounced in patients with cortical lesions. “Pathological completion” was most frequently observed for high BDs and for square fragments oriented towards the blind hemifield. Our findings confirm contour integration deficits in the intact VF of hemianopia patients. Further, our results indicate that (1) contour integration deficits are exacerbated by contextual interaction and (2) “pathological completion” appears to be more likely associated with lesions of cortical rather than geniculo-striate origin. The deficits point to increased lateral suppressive inputs from background elements.