Differential Effects of tDCS on Working and Long-term Memory During Visual Search

Poster Session A - Saturday, March 29, 2025, 3:00 – 5:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Poopa Kaewbuapan^1,2 (poopa1111@gmail.com), Duanghathai Wiwatratana², Sirawaj Itthipuripat²; ¹School of Information Technology, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand, ²Neuroscience Center for Research and Innovation, Learning Institute, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand

Visual search efficiency improves with repetition as target templates shift from working to long-term memory. The anodal transcranial direct current stimulation (tDCS) over the right posterior parietal cortex was reported to enhance working memory. However, the tDCS-stimulating effect of different cortical sites on the interaction between memory systems and attention during visual search remains unexplored. This study examines how tDCS influences the interaction between working memory, long-term memory, and attention during visual search. Nineteen participants (aged 18–35) completed a visual search task requiring memory of colored cues (red or green) and Landolt-C shapes, repeated across trials. Participants received 20 minutes of 2.0 mA anodal tDCS over the left or right posterior parietal cortex (PPC), right dorsolateral prefrontal cortex (DLPFC), or sham stimulation, with sessions separated by at least 48 hours. Behavioral results showed no significant difference in hit rates between real and sham stimulation, though left PPC stimulation modestly reduced reaction times. EEG data revealed that the right DLPFC stimulation enhanced contralateral delay activity in early trial repetitions, supporting improved visual working memory capacity. Both right DLPFC and left PPC amplified the N2pc component in mid-sequence trials, indicating enhanced attention guided by memory templates. Uniquely, the right PPC stimulation increased late positive complex activity during early and mid-repetition phases, suggesting facilitation of working-to-long-term memory transfer and highlighting functional lateralization within PPC. These findings underscore anatomically specific roles of PPC and DLPFC in modulating memory and attention processes during visual search.

Topic Area: ATTENTION: Development & aging