Pupillary and reaction time measures of sustained processing of negative information in depression

Background: Disruptions of emotional information processing (i.e., attention to, memory for, and interpretation of emotional information) have been implicated in the onset and maintenance of depression. The research presented here investigated cognitive and psychophysiological features of a particularly promising correlate of depression: sustained processing of negative information 4–5 sec after an emotional stimulus. Methods: Pupil dilation data and reaction times were collected from 24 unmedicated depressed and 25 nondepressed adults in response to emotional processing tasks (lexical decision and valence identification) that employed idiosyncratically generated personally relevant and normed stimuli. Pupil dilation was used to index sustained cognitive processing devoted to stimuli. Results: Consistent with predictions, depressed individuals were especially slow to name the emotionality of positive information, and displayed greater sustained processing (pupil dilation) than nondepressed individuals when their attention was directed toward emotional aspects of information. Contrary to predictions, depressed participants did not dilate more to negative than positive stimuli, compared to nondepressed participants. Conclusions: These data suggest depressed individuals may not initially attend to emotional aspects of information but may continue to process them seconds after they have reacted to the information.