Audio-Visual Stimulation to Enhance EEG Theta and Episodic-Memory Consolidation

Poster Session C - Sunday, March 30, 2025, 5:00 – 7:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Tashi Lhamo¹ (tashilhamo2026@u.northwestern.edu), Nathan W. Whitmore², Ken A. Paller¹; ¹Northwestern University, ²Massachusetts Institute of Technology

Theta EEG rhythms have been linked with memory encoding and retrieval in both animal and human studies. Is theta also associated with post-encoding consolidation? Multiple methods for altering theta have been used to address this question. For example, Shtoots and colleagues (2024) applied transcranial-alternating-current stimulation (tACS) after learning and found improved recall for frontal theta stimulation compared to parietal theta, frontal beta, and sham stimulation. During tACS, assessing the electroencephalogram (EEG) during and after stimulation is difficult. In our experiment, we attempted to replicate the recall improvement using a different method to increase theta. Custom-built goggles emitted light flashes and sounds at 6 Hz as a sensory-entrainment tool. In a learning phase, 30 objects were shown for 3 seconds each followed by a recall test. This sequence was repeated three times, improving recall to an average accuracy of 60-70% correct. Next, participants received 20 minutes of sensory entrainment or control stimulation. Recall was tested after three delays: 2 hr, 24 hr, and 7 days. Preliminary data showed a recall decline, as expected. We further predict that theta stimulation will enhance consolidation compared to the control condition, leading to reduced forgetting across the three delays. We will also analyze theta power in each participant to look for relationships with memory performance. This research seeks a better understanding of offline memory consolidation and the potential role of theta rhythms. Based on such progress, new strategies may be developed to help people who are experiencing memory difficulties.

Topic Area: LONG-TERM MEMORY: Episodic