M80. ALTERATIONS IN TEMPORAL PROCESSING AFFECT SCHIZOPHRENIA AND BIPOLAR PATIENTS AT DIFFERENT TEMPORAL SCALES
Authors: Polgari Patrik , Weiner Luisa , Bertschy Gilles , Giersch Anne 
Published: May 2020

Abstract

Background
Previous work suggested that patients with Schizophrenia (SZ) and Bipolar disorder (BP) both show anomalies in temporal cognition, although at different temporal scales. Recent results suggest disruptions in the processing of sensory information in time in SZ at the sub-second scale, including temporal order processing (100s ms). On the other hand, BP patients often report tachypsychia or racing thoughts, a subjective acceleration in the production of thoughts, which points towards temporal anomalies at the (supra-)second scale.

Methods
To further investigate the proposed temporal abnormalities which differentially affect the two groups, 11 SZ patients, 14 BP patients and 21 healthy controls (HC) performed two tasks. First, subjects’ ability at ordering events in time was evaluated in a Temporal Order Judgment task. Participants were presented two squares separated by either a sub-threshold 17ms or a supra-threshold 100 ms asynchrony, or two squares appearing simultaneously on a computer screen. They were instructed to respond, by clicking on one of two response-buttons, to the side of the first stimulus and their accuracy was recorded. In a second task, subjects were presented the ambiguous Necker cube figure and were instructed to report, via button presses, each time their perception of the figure changed between the two possible interpretations. Two attentional conditions were used: a “Spontaneous” condition where subjects reported perceptual changes that occurred spontaneously (without any attentional control), and a “Focus” condition where subjects were asked to focus on and mentally maintain one of the two interpretations of the figure for as long as possible and switch back to it in case of perceptual reversal. Eye movements and manual responses were recorded during this task and were used to compute two measures: “manual windows” based on subject’s explicit responses and reflecting time intervals of stable percepts of the figure, and “ocular windows” based on ocular fixations and reflecting implicit and automatic alternations between the two interpretations of the figure. The rates and durations of the two “windows” were compared in the two attentional conditions.

Results
We present preliminary results. In the Temporal Order Judgment task SZ patients’ accuracy was significantly lower than that of HC for visible 100 ms asynchronies. BP patients’ performance had intermediate values and did not differ from the other groups. For sub-threshold 17 ms asynchronies no significant difference was found between groups.
In the Necker cube task, similar rates of “manual windows” were found in all three groups, however there was a tendency towards an increased window duration in the Focus condition in BP patients. The rate of “ocular windows” was significantly higher in BP patients compared to HC and SZ patients, with decreased “ocular window” duration in BP patients compared to HC. BP patients’ rate of “ocular windows” increased mainly in the “Focus” condition.

Discussion
The findings in the Temporal Order Judgment task replicate results in the literature showing an impaired temporal order processing in SZ patients for supra-threshold asynchronies at the scale of 100s ms. The results of the Necker cube task suggest that BP patients cannot help oscillating between the two interpretations of the Necker cube. Complementary results obtained in a larger group of BP patients suggest a link with tachypsychia. Our present results support the idea that temporal cognition is altered in both SZ and BP patients but at different temporal scales.