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Accueil du site > Séminaires LNC > séminaires à venir (upcoming seminars)

Anne Giersch

Temporal simultaneity and order : what can we learn from patients with schizophrenia ?

Results observed in patients with schizophrenia question the mechanisms underlying temporal event-coding. At a clinical level these patients display a disturbed sense of continuity. Experimentally, they are impaired in temporal order judgments and in discriminating between simultaneous and asynchronous events, this possibly accounting for a disordered sense of time continuity. However, recent studies showed that ‘simultaneous’ responses are not associated with a fusion of events in time, as usually believed. This leads us to question the mechanisms underlying the sense of time continuity. During the tasks, subjects decided whether two squares were displayed simultaneously or asynchronously, and gave their response by hitting a left or right response key. We repeatedly showed that when stimuli are asynchronous and displayed on opposite sides, manual responses are biased to the side of either the first or second stimulus. Such a bias allowed us to explore the implicit processing of asynchronies when those are not explicitly detected by subjects. Results show that patients distinguish events in time at an implicit level even when explicitly judging such events to be synchronous. In addition, their implicit responses differ qualitatively from those observed in controls, for asynchronies as short as 8-17 ms. There is a clear dissociation between results at short and large asynchronies, that question the mechanisms underlying the implicit coding of events in time, not only in patients, but also in controls. It is as if controls would follow events in time at an implicit level, even when asynchronies are shorter than 20 ms, whereas patients cannot. We will show recent results confirming these hypotheses more directly in healthy volunteers. We used an original priming paradigm to explore to which extent temporal relationships are coded within temporal windows of subjective simultaneity. We will discuss the possible role of these mechanisms in the sense of time continuity.