Schizophrenia Bulletin Advance Access published online on March 21, 2008
Schizophrenia Bulletin, doi:10.1093/schbul/sbn016
Extended Visual Simultaneity Thresholds in Patients With Schizophrenia
2 INSERM U666; Centre Hospitalier Régional de Strasbourg, Pôle de Psychiatrie, BP 406, 67091 Strasbourg Cedex, France
3 Department Psychologie, Ludwig-Maximilians Universität, 80802 München, Germany
4 Department of Psychiatry and Psychotherapy; RWTH Aachen University, Pauwelstrasse 30, 52074 Aachen, Germany
5 Department of Psychology National University of Ireland, Galway, Republic of Ireland
1 To whom correspondence should be addressed; tel: 0033-0-3-88-11-64-61, fax: 0033-0-3-88-11-64-46, e-mail: giersch{at}alsace.u-strasbg.fr.
Clinical observations suggest that the experience of time phenomenology is disturbed in schizophrenia, possibly originating disorders in dynamic cognitive functions such as language or motor planning. We examined the subjective evaluation of temporal structure using an experimental approach involving judgments of simultaneity of simple, visually presented stimuli. We included a priming procedure, ie, a subthreshold presentation of simultaneous or asynchronous stimuli. This allowed us to evaluate the effects of subthreshold synchrony and to check for bias effects, ie, changes in the criteria used by the subjects to rate the stimuli. Primes were adapted to the responses of the subjects. Bias effects were thus expected to yield a change in the efficiency of the prime and to induce a change in the amplitude of the priming effect. Nineteen outpatients with schizophrenia and their individually matched controls participated in the study. In all tests, patients required longer delays between stimuli to detect that they were asynchronous. In other words, they judged stimuli to be synchronous even when their onset was separated by delays of 100 milliseconds and even more in some cases. These results contrasted with preserved effects of subthreshold synchrony. Our findings argue against the hypothesis that the patients’ responses were influenced by biases. We conclude that the subjective evaluation of simultaneity/asynchrony is impaired in schizophrenia, thus leading to impairment in the phenomenology of event-structure coding. The method used in the present study provides a novel approach to the assessment of those disturbances related to time in patients with schizophrenia.
Keywords: time processing / visual perception / psychophysics / consciousness / synchrony