Bilateral transcranial direct current stimulation over the posterior parietal cortex enhances recognition memory in healthy individuals

There is emerging evidence from imaging studies that the parietal cortex plays an active role in recognition memory, however, its functional contribution is still under debate. To evaluate the potential role of the PPC (posterior parietal cortex) for episodic memory retrieval, 14 healthy participants received tDCS (transcranial direct current stimulation) over PPC by using a sham-controlled, counterbalanced, single-blinded study design. Participants were randomly assigned into two separate groups, where 7 participants received real tDCS (1.5 mA for 15 min) and 7 participants (matched on age, gender and years of education) received sham stimulation (1.5 mA for 30 s) during the recognition part of the word-list learning paradigm. In both groups, the anodal electrode was placed over the P3 and the cathodal electrode over the P4 (35 cm2 each) by using the international 10/20 system. Accuracy and reaction times of recognition memory were measured immediately and 24 h after the initial episodic memory encoding. We found that recognition performance for episodic memory was better during verum than during sham tDCS. This difference was marginally significant 24 h later. No differences were found for RTs. Our results show that bilateral tDCS over the PPC significantly enhanced recognition memory performance during immediate recognition and possibly have an effect on post-learning processing.