The guarantee of perceptual coherence for events through everyday life situations depends upon the capacity to correctly integrate series of multi-sensory experiences. Patients with schizophrenia have been shown to reveal a deficit in integrating, i.e., "binding", perceptual information together. However, results in the literature have also suggested the reverse effect. Indeed, in certain paradigms patients have revealed more binding phenomenon than healthy controls and reported experiencing two distinct events as occurring "together". This finding suggests that patients may require longer time intervals between two distinct events before being able to perceive them as "one-after-the-other". The question here was to test whether this perceptual binding abnormality in schizophrenia is confined to events within the same modality or whether it is also present across sensory modalities. Thirty patients with schizophrenia were compared with 33 normal controls using a simultaneity judgement paradigm. There were two uni-modal conditions in which stimuli were presented in the same modality (visual or auditory) and one bimodal condition (audio-visual). Participants were presented with stimuli varying across a range of inter-stimulus intervals (ISI). They were required to judge whether they experienced two stimuli as occurring "together" or "one-after-the-other". Compared to controls and in all conditions, patients needed larger ISI to experience two stimuli as "one-after-the-other" (all ISI × Group interactions p < 5 · 10- 5). These abnormalities correlated with the disorganization dimension but not with the dosage of chlorpromazine equivalent. The increase of the time interval needed to perceive two stimuli as "one-after-the-other", reflect an abnormally low time resolution in patients with schizophrenia. We discuss the possible involvement of anatomical disconnectivity in schizophrenia which would specifically affect the time integration properties of neural assemblies. © 2007 Elsevier B.V. All rights reserved.
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