Depression symptom dimensions and asymmetrical frontal cortical activity while anticipating reward

Abstract

Unipolar depression has been characterized as involving diminished approach motivation and reward sensitivity. A psychophysiological indicator of approach motivation involves an asymmetry in frontal EEG activity, such that greater left relative to right frontal cortical activity indicates increased approach motivation. Consistent with the perspective of reduced approach motivation tendencies, depression has been associated with decreased relative left frontal cortical activity. To date, supporting research has primarily relied on categorical diagnoses or composite symptom counts. However, given the heterogeneity in depression, it is unclear what specific symptom dimensions relate to decreased relative left frontal cortical activity. The present study examined the association between multiple depression symptom dimensions and asymmetrical frontal cortical activity while anticipating reward in separate undergraduate (n = 75) and clinical samples (current major depressive disorder [n = 68] and never depressed controls [n = 67]). All participants completed the Inventory of Depression and Anxiety Symptoms, a self-report measure of factor-analytically derived symptom dimensions. Frontal cortical activity was assessed during a computerized slot machine task while participants anticipated potential monetary reward or no incentive. In undergraduates with low depression symptoms and never depressed controls, reward trials relative to no-incentive trials elicited greater relative left frontal cortical activity. Furthermore, in both samples across all participants, increased dysphoria and lassitude symptoms were associated with decreased relative left frontal cortical activity while anticipating reward. The present study suggests that depression symptoms consistent with motivational disengagement are associated with decreased relative left frontal cortical activity.

Keywords: EEG; asymmetry; depression; dysphoria; lassitude; reward.

Figure 1

Frontal cortical activity while anticipating reward during the slot machine task for participants in Study 1 (top) and Study 2 (bottom). Participants with low versus high IDAS general depression scores in Study 1 were determined via a median split (median = 40). The y-axis represents increased frontal cortical activity during the reward relative to no incentive condition (i.e., reward – no incentive), and separate bars are presented for the left and right hemispheres. IDAS = Inventory of Depression and Anxiety Symptoms. * p < .05, ** p < .01

Figure 2

Scatterplots (top) and three-dimensional correlation coefficient head maps (bottom) depicting the association between IDAS dysphoria (left) and lassitude (right) symptom dimensions and relative left frontal cortical activity while anticipating reward relative to no incentive (i.e., reward – no incentive) in the undergraduate sample (N = 75). In the scatterplots, the y-axis represents increased relative left frontal cortical activity while anticipating reward. In the correlation coefficient head maps, brighter colors represent a stronger negative correlation between the symptom dimension and relative left frontal cortical activity while anticipating reward. IDAS = Inventory of Depression and Anxiety Symptoms.

Figure 3

Scatterplots (top) and three-dimensional correlation coefficient head maps (bottom) depicting the association between IDAS dysphoria (left) and lassitude (right) symptom dimensions and relative left frontal cortical activity while anticipating reward relative to no incentive (i.e., reward – no incentive) in the clinical sample (N = 135). In the scatterplots, the y-axis represents increased relative left frontal cortical activity while anticipating reward. In the correlation coefficient head maps, brighter colors represent a stronger negative correlation between the symptom dimension and relative left frontal cortical activity while anticipating reward. IDAS = Inventory of Depression and Anxiety Symptoms.