Intact modulation of response vigor in major depressive disorder

Abstract

Blunted motivation is a core symptom of Major Depressive Disorder (MDD). Although the empirical picture is mixed, cognitive processes that can be collectively referred to as reward processing have been found to be consistently muted in MDD; most notably, reward sensitivity and reinforcement learning. Works on the modulation of response vigor in individuals with MDD have examined various types of reward, but recent research has shown that in the general population, response vigor is not modulated by type of reward on tasks that are highly similar to those used in these experiments. The present study implemented a form of non-reward related reinforcement which has repeatedly been shown to modulate response vigor in the general population. It investigated whether modulation of response vigor by this type of reinforcement would be effective in individuals with MDD. Clinically depressed individuals (N = 121; 76 post-exclusion) engaged in a task in which their responses led to predictable and immediate sensorimotor effects, or no such effects. Response vigor increased when responses led to sensorimotor effects, which was comparable to the increase found in the general population. These findings support the utility of isolating the computations leading to different reinforcement types and suggest that motivational deficits in MDD may be specific to the type of reward (i.e., hedonically or otherwise explicitly desired stimuli). These results contribute to the literature by suggesting that the reinforcement from sensorimotor predictability stems from processes devolved to motor control, whereas reinforcement from rewards may depend on more general-purpose processes.