Schedule of Events | Symposia

Neural and Behavioral Rhythmicity for Retrieving Memories from More Than Four Items

Poster Session B - Sunday, March 30, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Takuya Ideriha¹ (ide3.ko@keio.jp), Junichi Ushiyama^2,3; ¹Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan, ²Faculty of Environment and Information Studies, Keio University, Fujisawa, Kanagawa, Japan, ³Department of Rehabilitation Medicine, Keio University School of Medicine, Keio University, Tokyo, Japan

Even under challenging conditions for memory recall, such as when we attempt to learn a large amount of information at the same time, we are still able to retrieve the target items. However, the neural processes that support such difficult memory retrieval are unclear. In this study, we report an intriguing phenomenon in which our nervous system recruits behavioral/neural rhythmicity in the theta-alpha band (4–13 Hz) to retrieve memory when the number of retained items is beyond four. Participants learned and retrieved 2–5 color/letter pairs in the experiments. Analyses of hundreds of reaction times revealed a significant tendency for memory recall to occur at discrete timings corresponding to theta–alpha cycles, but only when the number of memorized items was beyond four. Also, in data from Electroencephalography, we found significantly stronger stimulus/response-locked theta-alpha power when in the 5-pair condition compared with the 3-pair condition, supporting the consistent phase-locking of memory recall to theta-alpha neural rhythmicity. These findings suggest that neural rhythmicity supports memory retrieval under challenging situations when the number of retained items is beyond four, which is known as the "magical number," corresponding to the limit of our cognitive capacity.

Topic Area: LONG-TERM MEMORY: Other