Abstract
BACKGROUND: Major depressive disorder has been associated with specific attentional biases in processing emotional facial expressions: heightened attention for negative and decreased attention for positive faces. However, using visual search paradigms, previous reaction-time-based research failed, in general, to find evidence for increased spatial attention toward negative facial expressions and reduced spatial attention toward positive facial expressions in depressed individuals. Eye-tracking analyses allow for a more detailed examination of visual search processes over time during the perception of multiple stimuli and can provide more specific insights into the attentional processing of multiple emotional stimuli. METHODS: Gaze behavior of 38 clinically depressed individuals and 38 gender matched healthy controls was compared in a face-in-the-crowd task. Pictures of happy, angry, and neutral facial expressions were utilized as target and distractor stimuli. Four distinct measures of eye gaze served as dependent variables: (a) latency to the target face, (b) number of distractor faces fixated prior to fixating the target, (c) mean fixation time per distractor face before fixating the target and (d) mean fixation time on the target. RESULTS: Depressed and healthy individuals did not differ in their manual response times. Our eye-tracking data revealed no differences between study groups in attention guidance to emotional target faces as well as in the duration of attention allocation to emotional distractor and target faces. However, depressed individuals fixated fewer distractor faces before fixating the target than controls, regardless of valence of expressions. CONCLUSIONS: Depressed individuals seem to process angry and happy expressions in crowds of faces mainly in the same way as healthy individuals. Our data indicate no biased attention guidance to emotional targets and no biased processing of angry and happy distractors and targets in depression during visual search. Under conditions of clear task demand depressed individuals seem to be able to allocate and guide their attention in crowds of angry and happy faces as efficiently as healthy individuals.