Time perception of simultaneous and sequential events in early-onset schizophrenia

Insights into the perceptual moment theory: Experimental evidence from simultaneity judgment

The perception appears to flow in a continuous pattern but evidence suggest that perception may involve discrete temporal sampling of peripheral cues. Stroud's perceptual moment theory proposes that perception occurs in discrete moments; however, more experimental evidence is required to support this theory. The present study characterized the decision function for asynchrony detection using variable stimulus-onset asynchronies (SOAs). Fourteen healthy volunteers (twelve males and two females), ages 21.5 ± 3.8 years (mean ± SD) participated in the study. A microcontroller was used to randomly present 280 events of paired stimuli (two red LEDs) with varying SOAs from -65 to 65 ms in steps of 5 ms. Participants were asked to press the "L" or "R" response key based on whether the left or right LED lit up first and to press the "S" key if they could not perceive the order. Asynchrony detection does not exhibit a fixed threshold value; instead, its decision function shows a monotonic increase with increasing SOAs. The asynchrony detection was 50% at an SOA of 27.8 ± 1.7 ms (mean ± SE). The curve plateaued off near 100% at SOA of 57.2 ms, which may correspond to the duration of one perceptual moment for visual perception. Data from a separate group of ten volunteers was used to validate the results. Results indicate that perception is temporally discretized rather than continuous, and the estimated duration of one perceptual moment is around 57.2 ms. This simple experiment gives objective evidence for Stroud's perceptual moment theory.

Positive symptoms and time perception in schizophrenia: A meta-analysis

Positive symptoms of schizophrenia may be related to distortions in time perception. To examine this issue, we conducted a meta-analysis to determine whether positive symptoms are associated with deficits in time processing performance. MEDLINE and Web of Science were searched from January 1980 through March 2017, and all related articles and their references were scrutinized to find relevant studies. Studies were selected if they included participants with a diagnosis of schizophrenia, and reported data from behavioral measures of interval timing (e.g. duration discrimination and temporal order judgement). The results indicated that positive symptoms of schizophrenia are related with overestimation of interval timing (i.e., acceleration of the “internal clock”), and suggest that time perception may be associated with psychosis.

Minimal Self and Timing Disorders in Schizophrenia: A Case Report

For years, phenomenological psychiatry has proposed that distortions of the temporal structure of consciousness contribute to the abnormal experiences described before schizophrenia emerges, and may relate to basic disturbances in consciousness of the self. However, considering that temporality refers mainly to an implicit aspect of our relationship with the world, disturbances in the temporal structure of consciousness remain difficult to access. Nonetheless, previous studies have shown a correlation between self disorders and the automatic ability to expect an event in time, suggesting timing is a key issue for the psychopathology of schizophrenia. Timing disorders may represent a target for cognitive remediation, but this requires that disorders can be demonstrated at an individual level. Since cognitive impairments in patients with schizophrenia are discrete, and there is no standardized timing exploration, we focused on timing impairments suggested to be related to self disorders. We present the case report of AF, a 22 year old man suffering from schizophrenia, with no antipsychotic intake. Although AF shows few positive and negative symptoms and has a normal neurocognitive assessment, he shows a high level of disturbance of Minimal Self Disorders (SDs) (assessed with the EASE scale). Moreover, AF has a rare ability to describe his self and time difficulties. An objective assessment of timing ability (variable foreperiod task) confirmed that AF had temporal impairments similar to those previously described in patients, i.e., a preserved ability to distinguish time intervals, but a difficulty to benefit from the passage of time to expect a visual stimulus. He presents additional difficulties in benefitting from temporal cues and adapting to changes in time delays. The impairments were ample enough to yield significant effects with analyses at the individual level. Although causal relationships between subjective and objective impairments cannot be established, the results show that exploring timing deficits at the individual level is possible in patients with schizophrenia. Besides, the results are consistent with hypotheses relating minimal self disorders (SDs) to timing difficulties. They suggest that both subjective and objective timing investigations should be developed further so that their use at an individual level can be generalized in clinical practice.