Pupillary Responses as a Biomarker of Diminished Effort Associated With Defeatist Attitudes and Negative Symptoms in Schizophrenia

Abstract

Background: The hypothesis that defeatist performance attitudes are associated with decreased goal-directed task effort and negative symptoms in consumers with schizophrenia was investigated by using pupillary responses as a biomarker of task effort. Pupillary dilation during cognitive tasks provides a biomarker of effort devoted to the task, with greater dilation indicating greater effort.

Methods: Defeatist attitudes were assessed in 149 consumers with schizophrenia or schizoaffective disorder and 50 healthy control subjects, and consumers were divided into three groups (tertile split) with respect to severity of defeatist attitudes. Pupillary dilation responses were recorded during a digit-span task with three-, six-, and nine-digit spans.

Results: Effort allocation (pupillary responses) to the task increased as the processing load increased from low (three-digit) to moderate (six-digit) demands in healthy control subjects and consumers with schizophrenia with mild and moderate severity of defeatist attitudes. In contrast, consumers with severe defeatist attitudes did not increase their effort when processing demands increased from low to moderate loads. These consumers showed significantly less effort in the six-digit condition relative to consumers with mild defeatist attitudes. Moreover, consumers with severe defeatist attitudes showed significantly greater severity of negative symptoms relative to consumers with mild defeatist attitudes and negative symptoms were significantly correlated with defeatist attitudes.

Conclusions: These results suggest a relationship between defeatist performance attitudes, goal-directed task effort indexed by pupillary responses, and negative symptoms in schizophrenia. The findings have implications for using cognitive therapy to reduce defeatist attitudes that may contribute to diminished effort and negative symptoms in schizophrenia.

Keywords: Dysfunctional attitudes; Effort; Motivation; Negative symptoms; Pupillometry; Schizophrenia.

Published by Elsevier Inc.

Figures

Figure 1

Pupillary responses (change in diameter in mm relative to baseline) are shown for consumers with schizophrenia (SZ) with low, moderate and severe defeatist performance attitudes (DPAS) and healthy controls in the 3-, 6-, and 9-digit span conditions. At trial onset, participants heard the word “ready” when the background luminance changed from dark to light, which triggered an initial light constriction reflex, and digits were presented at the rate of one per second (first digit was presented at 1 second, second digit at 2 seconds, etc.), until the word “repeat” prompted digit recall.

Figure 2

Pupillary responses (change in diameter in mm relative to baseline) are shown for consumers with schizophrenia (SZ) with low, moderate and severe defeatist performance attitudes (DPAS) and healthy controls at the time the last digit was presented in the 3- (4 sec), 6- (7 sec), and 9-digit (10 sec) span conditions. Error bars are 95% CI of mean.

Figure 3

Percent of digits recalled in correct order is shown for consumers with schizophrenia (SZ) with low, moderate and severe defeatist performance attitudes (DPAS) and healthy controls in the 3-, 6-, and 9-digit span conditions. Error bars are 95% CI of mean.

Figure 4

Negative symptom factor scores for Diminished Motivation and Diminished Expression are shown for consumers with schizophrenia (SZ) with low, moderate and severe defeatist performance attitudes (DPAS). Error bars are 95% CI of mean.