Oculomotor inhibition and location priming in schizophrenia

Abstract

Schizophrenia is widely thought to involve elevated distractibility, which may reflect a general impairment in top-down inhibitory processes. Schizophrenia also appears to involve increased priming of previously performed actions. Here, we used a highly refined eye-tracking paradigm that makes it possible to concurrently assess distractibility, inhibition, and priming. In both healthy control subjects (HCS, N = 41) and people with schizophrenia (PSZ, N = 46), we found that initial saccades were actually less likely to be directed toward a salient "singleton" distractor than toward less salient distractors, reflecting top-down suppression of the singleton. Remarkably, this oculomotor suppression effect was as strong or stronger in PSZ than in HCS, indicating intact inhibitory control. In addition, saccades were frequently directed to the location of the previous-trial target in both groups, but this priming effect was much stronger in PSZ than in HCS. Indeed, PSZ directed gaze toward the location of the previous-trial target as often as they directed gaze to the location of the current-trial target. These results demonstrate that-at least in the context of visual search-PSZ are no more distractable than HCS and are fully capable of inhibiting salient-but-irrelevant stimuli. However, PSZ do exhibit exaggerated priming, focusing on recently attended locations even when this is not beneficial for goal attainment. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Figure 1.

A. Each participant was assigned to a target group (diamond or circle), which remained constant throughout the experiment for that participant. Participants were instructed to report the orientation of the line inside the target. Distractors were heterogeneous shapes to prevent the target from popping out. The singleton was pink among green for half the participants in each diagnostic group and green among pink for the other half. B. Trials began with the presentation of a blank intertrial interval screen for 500 ms, followed by a screen containing the fixation cross; this screen remained visible until the participant maintained fixation within a 1.5° radius of the central fixation point for 500 ms. The search array then appeared and remained visible until the button-press response. C. The two types of trials with regards to location priming. The location of the target was randomly selected. On repeat-location trials, the target location from the previous trial (trial n−1) was also the target location on the current trial (trial n). On change-locations trials, the target location on the current trial was not the same as on the previous trial, so a distractor appeared at the primed location.

Figure 2.

A. Percentage of first saccades that landed on a given stimulus type (target, nonsingleton distractor, or singleton distractor). B. The individual data points indicate each’s subject’s mean difference score, which was used to quantify the extent to which gaze was directed toward the singleton when it was not directed toward the target. For trials on which the first fixation was not directed toward the target, we computed the percentage of trials on which the first fixation was directed to the singleton (rather than to one of the nonsingleton distractors).

Figure 3.

A. Percent of accurate responses (in reporting the tilt of the line within the target) and B. manual response times when the current-trial target was at the same location as the previous-trial target (repeat-location trials, left side of each panel) versus when the current-trial target was at a different location from the previous-trial target (change-location trials, right side of each panel).

Figure 4.

A. Heat maps of first saccade destinations for each angular distance between the target and primed location (Left panel for HCS, Right for PSZ). The heat maps have been rotated so the target appears at the top (12 o’clock) position. The white arrow points to location primed by the target from the previous trial. On repeat-location trials, the target on the current trial appears at the primed location. B. Percentage of first saccades to each search item (Target, Primed location, unprimed location) on change-location trials. C. The location priming effect was calculated as the difference score between percentage of first saccades directed to the primed location versus the average unprimed location. D.

Figure 5.

A. Latency for initial saccades to the target location on repeat-location trials verses change-location trials in each group and B. Percentage of saccades directed to the target location on repeat-location trials versus change-location trials in each group