Poster C69, Sunday, March 25, 1:00-3:00 pm, Exhibit Hall C
Hippocampal theta-gamma coupling predicts associative memory performance as measured by chronic ambulatory electrocorticography
Anita Shankar1, Simon Henin1, Daniel Friedman1, Patricia Dugan1, Lucia Melloni1,2, Werner Doyle1, Lila Davachi3, Anli Liu1; 1New York University School of Medicine, 2Max Planck Institute for Brain Research, 3Columbia University
Previously, increased hippocampal gamma power and theta-gamma coupling have predicted successful encoding of single items and word pairs, termed the subsequent memory effect. To investigate the mechanisms supportive of cross-modal learning, we examined physiological changes in the hippocampus in one epilepsy patient with chronic ambulatory electrocorticography (Responsive NeuroStimulator, Neuropace) and two patients undergoing invasive EEG for surgical evaluation as they participated in a novel associative memory task. During the task, face-profession pairs were presented simultaneously for an encoding period of five seconds, followed by a cued recall session in which patients were shown the face and asked to freely recall the paired profession. In our RNS patient, we observed a significant increase in gamma band (70-90 Hz) power during encoding in the 1500 – 2500 ms interval after stimulus presentation for subsequently recalled versus forgotten pairs. Furthermore, we observed a significant increase in theta-gamma phase amplitude coupling during successful encoding. We found similar increases in two surgical epilepsy patients predictive of successful encoding. We conclude that increased hippocampal theta-gamma coupling and an increase in gamma activity can predict successful encoding of cross-modal associations. Furthermore, that our patient with the RNS device demonstrated similar changes in hippocampal physiology compared to our surgical epilepsy patients suggests that chronic ambulatory electocorticography may serve as a useful platform for cognitive experiments, allowing for sensitive measurements of hippocampal physiology under controlled experimental conditions.
Topic Area: LONG-TERM MEMORY: Episodic