Antisaccade Deficits in Schizophrenia Can Be Driven by Attentional Relevance of the Stimuli

Abstract

The antisaccade task is considered a test of cognitive control because it creates a conflict between the strong bottom-up signal produced by the cue and the top-down goal of shifting gaze to the opposite side of the display. Antisaccade deficits in schizophrenia are thought to reflect impaired top-down inhibition of the prepotent bottom-up response to the cue. However, the cue is also a highly task-relevant stimulus that must be covertly attended to determine where to shift gaze. We tested the hypothesis that difficulty in overcoming the attentional relevance of the cue, rather than its bottom-up salience, is key in producing impaired performance in people with schizophrenia (PSZ). We implemented 3 versions of the antisaccade task in which we varied the bottom-up salience of the cue while holding its attentional relevance constant. We found that difficulty in performing a given antisaccade task-relative to a prosaccade version using the same stimuli-was largely independent of the cue's bottom-up salience. The magnitude of impairment in PSZ relative to control subjects was also independent of bottom-up salience. The greatest impairment was observed in a version where the cue lacked bottom-up salience advantage over other locations. These results indicate that the antisaccade deficit in PSZ does not reflect an impairment in overcoming bottom-up salience of the cue, but PSZ are instead impaired at overcoming its attentional relevance. This deficit may still indicate an underlying inhibitory control impairment but could also reflect a hyperfocusing of attentional resources on the cue.

Keywords: antisaccade; attention/hyperfocusing; inhibitory control; schizophrenia.

Fig. 1.

Task conditions and procedure. (A) In one condition, a single cue stimulus was presented at one of the 4 locations indicated. In another “pop-out” condition, colored disks appeared in each of the 4 locations, with 3 disks of one color and 1 disk of another color (either red or green and vice-versa)—in this example, red is the cue. In the “search” condition, all 4 locations had an equiluminant colored disk, but only one color was relevant—here, the red disk is the cue. For half of the participants within each group, the cue disk was red, and for the other half, it was green. The cue location was selected randomly on each trial. (B) At the beginning of each block, participants viewed an instruction screen indicating the condition (classic, pop-out, or search) and whether they should look toward the cue (pro-saccade) or to the mirror-image location (anti-saccade). (C) Each trial began with the appearance of the fixation point. Once the participant maintained gaze on the fixation point for 450 ms, it disappeared and a gap display consisting of location markers at each of the 4 locations appeared. After 200 ms, the gap display was replaced by the cue display (consisting of one cue and 0 or 3 distractors depending on the condition: in this example, the search condition is displayed). This was presented for 1000 ms, during which participants were required to shift their gaze toward or away from the cue location, followed by a blank post-trial interval of 1000–1800 ms.

Fig. 2.

Error rates for each condition. The mean percent of errors for prosaccade trials are displayed on the left side and those for antisaccade trials are presented on the right side. Error bars indicate the standard error of the mean.

Fig. 3.

(A) Latency distributions. Histograms represent relative frequency distributions of saccade latencies prosaccades (top panel) and antisaccades (bottom panel). Correct latencies are represented by darker colored histograms in the upper half of each plot, while erroneous latencies are plotted as vertically flipped histograms in lighter shading. Blue histograms represent data for HCS and red for PSZ. (B) Mean latencies for the 6 task combinations. The mean latencies for correct prosaccade trials are displayed on the left side and those for correct and incorrect antisaccade trials are presented on the right side of the figure. Bars displayed in lighter shading are mean latencies for erroneous saccades made to the cue instead of the mirror location.