Reducing negative affect with anodal transcranial direct current stimulation increases memory performance in young —but not in elderly—individuals

This study explores whether anodal transcranial direct current stimulation (tDCS) to the left dlPFC improves memory retrieval through the reduction of negative affect and if this interacts with age. We randomly assigned 94 healthy individuals (n = 43 young,n = 51 elderly) to either sham or active tDCS during encoding of a verbal episodic memory task. Participants completed two questionnaires assessing affective states pre- and post-stimulation. They had to recall items unexpectedly 20 min after encoding and to name which feelings were associated w ith this free recall. We applied mediation models to explore the relation between tDCS, change in affect, and memory retrieval. In young participants, the reduction of negative affect via anodal tDCS fully mediated the increase in memory retrieval (R2 = 57%;p <  0.001); that is, a stronger reduction of negative affect via tDCS led to better memory performance. We did not observe these effects in the elderly. Our study provides a further link between affect and memory: as increased activity in the dlPFC is crucial for successfully coping with affective in terference, anodal tDCS seems to help preventing irrelevant negative thoughts, thus foster attention allocation. Studies applying anodal tDCS to the left dlPFC in healthy young participants should consider changes in affect when interpreting the effect of stimulation on memory performance.

Source: Anatomy and Embryology - September 2, 2019 Category: Anatomy Source Type: research