Although functional neuroimaging studies of recognition memory consistently report activations in the left posterior parietal cortex (LPPC), very few neuropsychological or brain-stimulation studies provide evidence for a causal relationship between LPPC and memory retrieval. This study employed transcranial direct current stimulation (tDCS) to examine whether LPPC is required for memory retrieval. Anodal and cathodal tDCS are known to increase and decrease neuronal excitability respectively and it was predicted that, if LPPC is required for successful memory retrieval, such stimulation over this region with anodal or cathodal currents should lead to a concomitant increase or decrease in memory performance. Participants in the present experiment visited the laboratory twice for two source memory tests. In one visit, all participants received sham stimulation over the LPPC scalp region for a 10-minute interval between study and test phases. For the other visit, half of the participants received anodal stimulation and the other half received cathodal stimulation. The old/new recognition performance was found to increase after anodal stimulation and decrease after cathodal stimulation. No such effects were found in a control experiment where left primary motor cortex was stimulated. These findings provide evidence for the causal relationship between LPPC and retrieval processes in recognition memory.
- Posterior parietal cortex
- Recognition memory