[P3] Poster: Day 3

[P3-02] Implicit, but not explicit, timing is perturbed in schizophrenia

*Jennifer T Coull¹, Laurie Ladame¹, Mounira Taghdouini Kaddour¹, Tiffanie Zemour¹, Hélène Wilquin¹ (1. Centre for Research in Psychology & Neuroscience, CNRS & Aix-Marseille University (France))

Keywords:

temporal prediction,interval duration,duration estimation,foreperiod,statistical learning

Individuals with schizophrenia (SZ) have difficulty estimating periods of time in the peri-second range. However, it remains unclear whether these difficulties index a specific problem in representing time or are a secondary consequence of their more general cognitive disturbance. To address this question, we compared explicit (temporal generalisation) and implicit (temporal expectation) measures of timing in 13 individuals with SZ to that of 29 age-matched controls. In both tasks, the reference interval was 600ms and test intervals varied from 240 to 960ms. In the explicit task, the reference interval was presented on every trial and participants judged whether the variable test interval was the same or different to the reference. In the implicit timing task, participants had to simply respond as quickly as possible to the second of the two stimuli delineating the variable interval. Importantly, the 600ms test interval was four times more probable than the six shorter or longer intervals, which were themselves equally probable. Task order was counterbalanced across participants. Results showed that in the explicit timing task, as expected, the proportion of “same” responses was maximal for the 600ms interval and gradually decreased for increasingly shorter or longer test intervals in an inverted U-shape profile. Correspondingly, in the implicit timing task, mean RT was fastest for the 600ms interval and became gradually slower for shorter or longer intervals in a U-shaped profile. Moreover, analyses revealed that individuals with SZ were as accurate and precise as healthy controls on our explicit timing task in which the reference interval was presented on every trial. By contrast, in the implicit task individuals with SZ significantly overestimated the reference interval compared with healthy controls. This task dissociation suggests that explicit timing in SZ could, in fact, be intact. However, the temporal priors that are formed from temporally predictable information, and used to guide performance in the implicit task, appear to be distorted in individuals with SZ.