Reduced Affective Biasing of Instrumental Action With tDCS Over the Prefrontal Cortex

BACKGROUND Instrumental action is well known to be vulnerable to affective value. Excessive transfer of affective value to instrumental action is thought to contribute to psychiatric disorders. The brain region most commonly implicated in overriding such affective biasing of instrumental action is the prefrontal cortex. OBJECTIVE The aim of the present study was to reduce affective biasing of instrumental action using transcranial direct current stimulation (tDCS) in young healthy human volunteers. METHODS In a double-blind, randomized between-group design, 120 participants received anodal, cathodal and sham tDCS while at the same time (online) performing a task that assessed affective biasing of instrumental action. We placed tDCS electrodes over the anterior part of the prefrontal cortex based on evidence from brain stimulation work demonstrating the role of this brain region in controlling affective biasing of instrumental action. RESULTS We showed that prefrontal tDCS reduced affective biasing of instrumental action. Specifically, prefrontal tDCS reduced the degree to which aversive (versus appetitive) cues potentiated instrumental avoidance and suppressed instrumental approach. Contrary to our hypothesis, this effect was seen for cathodal tDCS rather than anodal tDCS. CONCLUSION The results demonstrate the potential utility of prefrontal tDCS as a tool for reducing affective biasing of instrumental behavior, thus opening avenues for interventional research on psychiatric disorders that implicate excessive transfer of affective value.