The Influence of Effort on Impairments of Attention Associated with Major Affective Disorders

Abstract

That neuropsychological performance is impaired in patients with affective disorders is now widely accepted, and there is growing evidence that attentional dysfunction (effortful attention in particular) is one of the major impairments normally observed. The present study aimed at defining the nature of attentional dysfunction in depression by means of tests designed to measure specific aspects of attention, such as sustained, selective, focused, divided attention, etc. We also tested the effect of increasing effortful attentional demands on subjects' performance. To that end, effort level was increased on the task variable that was considered to be the defining characteristic of each task. For example, the Stroop Color-Word is a test of perceptual interference, so that on the high effort condition we presented two types of interference - visual as well as auditory (recorded messages). Fourteen unipolar and thirteen bipolar patients were recruited from the inpatient psychiatry unit at the University of Massachusetts Medical Center, based on DSM-III criteria and score on the Inventory to Diagnose Depression (IDD). An age and education matched control group (N=20) was recruited from hospital workers. Subjects were administered a battery of twenty neuropsychological tests, including: Computerized Stroop Test, Continuous Performance Test, Trail Making, Symbol-Digit Modalities Test, Finger Tapping & Controlled Word Generation, Visual Letter Search, Digit Span, and a Levels of Processing Memory task. For each of these tasks, a low and high effort levels were employed. Subjects filled out two self-report scales, Fatigue Assessment Inventory and Profile of Mood States, before and after testing. Both unipolar and bipolar patients exhibited severe depression as measured by the IDD. ANOVA procedures indicated that on most measures patients performed significantly poorly when compared to normal controls (p<.0001), except for the Visual Letter Search. With respect to the dimension of effort, all subjects performed more poorly on high effort task demands (p<. 001). Interaction of effort by diagnosis was statistically significant for the following tasks: Stroop error rate, Trail Making, Symbol Coding, and Concurrent Response Production, indicating greater decrements in patients' performance relative to controls. While various attentional processes were affected, greatest impairments occurred on tasks requiring sustained and focused attention, under conditions of high effortful task demand. A discriminant function analysis showed that subjects were correctly classified to their respective groups with high accuracy level (85%).