Increased neural sensitivity to self-relevant stimuli in major depressive disorder

Abstract

The current research examined how individuals with depression process emotional, self-relevant stimuli. Across two studies, individuals with depression and healthy controls read stimuli that varied in self-relevance while EEG data were recorded. We examined the late positive potential (LPP), an ERP component that captures the dynamic allocation of attention to motivationally salient stimuli. In Study 1, participants read single words in a passive-viewing task. Participants viewed negative, positive, or neutral words that were either normative or self-generated. Exploratory analyses indicated that participants with depression exhibited affective modulation of the LPP for self-generated stimuli only (both positive and negative) and not for normative stimuli; healthy controls exhibited similar affective modulation of the LPP for both self-relevant and normative stimuli. In Study 2, using a separate sample and a different task, stimuli were provided within the context of sentence stems referring to the self or other people. Participants with depression were more likely to endorse negative self-referent sentences and reject positive ones compared to healthy controls. Depressed participants also exhibited an increased LPP to negative stimuli compared to positive or neutral stimuli. Together, these two studies suggest that depression is characterized by relatively increased sensitivity to affective self-relevant stimuli, perhaps in the context of a broader reduction in emotional reactivity to stimuli that are not self-relevant. Thus, depression may be characterized by a more nuanced pattern based on the degree of stimulus self-relevance than either a global decrease or increase in reactivity to affective stimuli.

Keywords: ERPs; LPP; depression; emotion; self-reference; sentence processing.

Fig. 1.

A. Grand average waveforms from CP1 and CP2 presenting the results of Study with the analyzed window of the LPP highlighted. Normative words are in the upper row while idiographic words are in the lower row; healthy controls are in the left column while depressed participants are in the right column. Note that negative polarity is up. Dashed gray lines are trials with neutral words, solid blue lines represent trials with pleasant words, while solid lines represent trials with positive words B. Topographic maps depicting the subtraction neutral from pleasant (left) and from unpleasant words (right) for healthy controls (two leftmost maps) and depressed individuals (two rightmost maps). Normative words are in the top row while idiographic words are in the lower row.

Fig. 2.

Line graphs depicting behavioral response for Study 2 with percent affirmations (left) and response time to each sentence type (right). Note that depressed individuals (dashed line), compared to healthy controls (solid line) were slower and more likely to affirm negative statements and reject positive statements; there was no significant difference between the groups’ behavior for neutral statements. Error bars represent 1 SEM.

Fig. 3.

A.Grand average waveforms depicting from electrode CPz from Study 2 with the analyzed window of the LPP highlighted. Healthy controls are in the left column while depressed participants are in the right column. Dashed gray lines indicate trials with neutral words, red solid lines represent trials with unpleasant stimuli, while solid blue represent trials with pleasant stimuli. Note that negativity is facing up. B. Topographical maps depicting the areas of activation for the analyzed window with red indicating positive polarity and blue represents negative.