Modulation of decision-making in a gambling task in older adults with transcranial direct current stimulation

Cognitive performance usually declines in older adults as a result of neurodegenerative processes. One of the cognitive domains usually affected is decision-making. Based on our recent findings suggesting that non-invasive brain stimulation can improve decision-making in young participants, we studied whether bifrontal transcranial direct current stimulation (tDCS) applied over the right and left prefrontal cortex of older adult subjects can change balance of risky and safe responses as it can in younger individuals. Twenty-eight subjects (age range from 50 to 85 years) performed a gambling risk task while receiving either anodal tDCS over the right and cathodal tDCS over the left dorsolateral prefrontal cortex (DLPFC), anodal tDCS over the left with cathodal tDCS over the right DLPFC, or sham stimulation. Our main finding was a significant group effect showing that participants receiving left anodal/right cathodal stimulation chose more often high-risk prospects as compared with participants receiving sham or those receiving right anodal/left cathodal stimulation. This result is contrary to previous findings in young subjects, suggesting that modulation of cortical activity in young and elderly results in opposite behavioral effects; thus supporting fundamental changes in cognitive processing in the elderly.