Examining the Neural Dynamics of Semantic Memory Integration Using Noninvasive Brain Stimulation with Concurrent EEG

Poster Session C - Sunday, April 14, 2024, 5:00 – 7:00 pm EDT, Sheraton Hall ABC

Evangelia G. Chrysikou¹, Alexa Gorman¹, Alexandra E. Kelly¹, Yoed N. Kenett²; ¹Drexel University, ²Technion-Israel Institute of Technology

Our experience shapes the structure of our knowledge in short- and long-term contexts (e.g., problem-solving, learning). Despite its importance, how knowledge is organized across individuals and how this structure may change over time is far from understood. Here, we investigated how the brain supports these dynamic processes using EEG concurrently with transcranial direct current stimulation (tDCS) to assess how facilitating or inhibiting activity in the angular gyrus (AG), a region important for integrating semantic information, affects the dynamic restructuring of relationships between concepts in long term memory. Participants first rated relatedness between all pairwise combinations of 20 concepts (N = 190 ratings). During tDCS of 2mA over the left AG, they performed a conceptual combination task requiring them to integrate new information about the same concepts they previously evaluated. Following stimulation, they performed the same relatedness judgments again. Participants received cathodal, anodal, and sham stimulation to AG across 3 counterbalanced sessions. The relatedness judgments before and after stimulation were analyzed using graph theoretical methods to construct semantic memory networks that were compared to test for changes in the structure of conceptual knowledge as a result of the semantic integration task performed under stimulation. The EEG data were analyzed using event-related potential (ERP) methods and showed how these restructuring effects are related to the N400 component, a well-established marker of semantic processing. We discuss the implications of these findings for our understanding of the restructuring of knowledge through the course of experience and its consequences for successful learning and problem solving.

Topic Area: LONG-TERM MEMORY: Semantic