Relation of depression symptoms to sustained reward and loss sensitivity

Abstract

Depression is characterized by altered sensitivity to rewards, with recent evidence suggesting that the ability to sustain responses to rewards across long experimental tasks is diminished. Most work on sustained reward responsiveness has taken a categorical approach and focused on major depressive disorder. However, impairments in reward sensitivity are also found at lower levels of symptom severity and may be relevant for understanding basic mechanisms linking reward processing abnormalities to depression. The current study took a dimensional approach to examine the relation between depression symptoms and sustained reward responsiveness by examining how early neural responses to rewards and losses change over a short time course (i.e., during the experiment). In a sample of 45 unselected undergraduates, changes in the amplitude of the reward positivity (RewP) and feedback negativity (FN) were examined over the course of a simple gambling task using multilevel modeling. Amplitude of the RewP was sustained and amplitude of the FN increased during the task. Unlike prior work focused on clinical populations, depression symptoms in this unselected sample were associated with enhanced RewP and FN responding over the course of the task. Results echo prior work that underscores the importance of examining changes in response to reward across trials and further suggests that sustained responses to both rewards and losses vary in relation to symptom level.

Keywords: ERPs; depression; young adults.

Figure 1.

Overview of the simple guessing paradigm (doors task) used to elicit the FN. Two doors are presented and participants are instructed to select either the left or right door within four seconds, using the left and right buttons on a mouse. A fixation cross is then presented for 1000ms, following which participants receive feedback on whether they guessed incorrectly (red downward arrow) and lost 25 cents, or guessed correctly (green upward arrow) and won 50 cents. Feedback is presented for 2000ms, following which a fixation cross is presented for 1500ms. Participants are then instructed to begin the next trial.

Figure 2.

(A) Grand-averaged RewP and FN across all participants in response to rewards and losses at electrodes Cz, Fz, FCz, F1, F2, FC1, FC2, C1 and C2 (left). The onset of the stimulus is denoted by a solid line. Dotted lines indicate the interval in which the mean RewP/FN amplitude was quantified (250-350 ms). Positive amplitudes are plotted downward per ERP convention. (B) The scalp topography (right) representing the difference waveform (∆RewP; gain-loss difference) for the interval 250-350ms following onset of the stimulus.

Figure 3.

The slopes associated with mean change in RewP/FN amplitude over the course of the task, plotted separately for reward (RewP) vs. loss (FN) conditions and for participants with relatively elevated depression (≥1 SD above the mean, ≥62T) and those with relatively low depression scores (≤1 SD below the mean, ≤42T), calculated from Model 1. As the FN is a negative deflection, negative slopes indicate that the FN became larger over the course of the task. As the RewP is a positive deflection, more positive slopes indicate that RewP became larger over the course of the task. Shaded areas represent ±1 standard error in model predictions.