Perceptual inference, accuracy, and precision in temporal reproduction in schizophrenia

Abstract

Accumulating evidence suggests that deficits in perceptual inference account for symptoms of schizophrenia. One manifestation of perceptual inference is the central bias, i.e., the tendency to put emphasis on prior experiences over actual events in perceiving incoming sensory stimuli. Using an interval reproduction task, this study aimed to determine whether patients with schizophrenia show a stronger central bias than participants without schizophrenia. In the interval reproduction task, participants were shown a cross on a screen. The cross was replaced with a Gaussian patch for a predetermined time interval, and participants were required to reproduce the interval duration by pressing and releasing the space key. We manipulated the uncertainty of prior information using different interval distributions. We found no difference in the influence of prior information on interval reproduction between patients and controls. However, patients with SZ showed a stronger central bias than healthy participants in the intermediate interval range (approximately 450 ms to 900 ms). It is possible that the patients in SZ have non-uniform deficits associated with interval range or uncertainty of prior information in perceptual inference. Further, the severity of avolition and alogia was correlated with the strength of central bias in SZ. This study provides some insights into the mechanisms underlying the association between schizophrenic symptoms and perceptual inference.

Keywords: Central bias; Perceptual inference; Schizophrenia; Time perception; Uncertainty adjustment.

Fig. 1

Experimental interval reproduction task. (A) Sequence of events during a trial. First, participants' attentions were fixated on a cross, and they were instructed to maintain fixation throughout the trial. After a random delay (0.5–1.2 s), a Gaussian patch (visual disk) was displayed for a specific interval (sample interval). Participants were instructed to reproduce the interval by pressing and holding the space key when the word ‘reproduction’ appeared. (B) Distribution of sample intervals. The wide distribution width was designed to produce high levels of uncertainty; the narrow distribution width was designed to produce low levels of uncertainty. The narrow distribution width comprised three interval ranges with different medians as follows: short interval range, 0.32 s; intermediate interval range, 0.64 s; and long interval range, 1.2 s. The wide distribution width comprised a single interval range with seven intervals having a median interval time of 0.64 s and a step size of log 0.15.

Fig. 2

Mean coefficient of variance (CV) for trial N and N-1. Error bars show bootstrapped 95% confidence intervals. HC, healthy controls group; SZ, patients with schizophrenia group.

Fig. 3

Mean reproduction durations of sample intervals in the narrow and wide distribution widths wherein the slope of the line provides an index for the strength of central bias. Error bars show bootstrapped 95% confidence intervals. Solid lines show best-fitting linear regressions for each range, whereas the dotted diagonal lines denote veridical (unbiased) performance. The filled circles show the values for the short interval range, the triangles show values for the intermediate interval range, the squares show values for the long interval range, and the open circles show values in the wide distribution width. HC, healthy controls group; SZ, patients with schizophrenia group. HC, healthy controls group; SZ, patients with schizophrenia group.

Fig. 4

CV versus VE for the reproduced durations of intervals from the narrow and wide distribution widths. VE (vertical error) refers to the degree of similarity between perceived and actual timing, and CV (coefficients of variation) indicates the precision of perceived timing. Error bars show bootstrapped 95% confidence intervals. The filled circles show the values for the short interval range, the triangles show values for the intermediate interval range, the squares show values for the long interval range, and the open circles show values in the wide distribution width. HC, healthy controls group; SZ, patients with schizophrenia group; CV, coefficients of variance; VE, vertical error.