Disturbances of multisensory processing in schizophrenia spectrum disorders : a behavioural and neurophysiological account

Self-disorders have long been considered as a central nucleus of the schizophrenic experience. It has been suggested that such self-disturbances might be associated with abnormal multisensory integration and abnormal bodily self-awareness. The primary goal of this thesis was to explore the behavioural and neurophysiological markers of self-disturbances in schizophrenia and in high schizotypy (i.e. a sub-clinical trait linked to schizophrenia). Specifically, we aimed at (i) investigating the temporal acuity in individuals with low and high schizotypy (ii) measuring aspects of the neural responses to multisensory integration in low and high schizotypes (iii) exploring how body representation abnormalities in both schizophrenic patients and high schizotypes affect basic processes of self-perception. In line with previous research showing a reduced multisensory acuity in schizophrenia, results from Chapter Three revealed a significant relationship between the temporal window within which two stimuli are integrated (i.e. TWI), and schizotypal personality traits; namely, higher schizotypal traits are associated with wider TWIs. In Chapter Four, we provided evidence of a selective relationship between the TWI for visuo-tactile stimuli and the individual beta frequency (IBF), i.e, slower IBFs accounts for larger TWIs, and between the TWI and schizotypy, i.e. wider TWIs are linked to higher schizotypal traits. In Chapter Five, we have demonstrated that patients with schizophrenia possess more malleable body representations and that these abnormalities are linked to early markers of vulnerability to the disorder (i.e. basic symptoms). Finally, findings from Chapter Six revealed that the abnormalities in bodily self-awareness observed in schizophrenia might extend to schizotypy, suggesting that such abnormalities could represent a trait marker for schizophrenia proneness. All in all, our results suggest that the abnormalities in multisensory integration and bodily awareness observed in schizophrenia spectrum disorders might produce a distortion in the structure of self-experience and contribute to the emergence of the disorder.