Schedule of Events | Symposia

Rapid context changes at encoding disrupt hippocampal autocorrelation and reduce temporal clustering of free recall

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

Lindsay I. Rait¹, Guo Wanjia¹, Zhifang Ye¹, Sarah DuBrow, Brice A. Kuhl¹; ¹University of Oregon

The hippocampus is essential for linking memories of past experiences to rich contextual details—memory for ‘where’ or ‘when’ an event took place. In humans, context representations are thought to powerfully shape how memories are organized. This has been demonstrated by studies of free recall which show that individuals are more likely to successively recall items that were studied closer together in time (i.e., temporal clustering). At present, however, there is limited evidence linking context representations in the hippocampus and temporal clustering in free recall. In an fMRI experiment (n=38), we manipulated the rate of context change during memory encoding to test whether this influenced the stability of hippocampal representations (measured by autocorrelation) as well as the degree of temporal clustering during subsequent recall. Context was manipulated by alternating background scenes at different switch rates (low, medium, high) as a list of words was encoded. Afterwards, subjects freely recalled as many words as possible. While context switch rate had no effect on the total number of words recalled, it significantly influenced the degree of temporal clustering. Specifically, a higher context switch rate was associated with less temporal clustering. Strikingly, this pattern of data was mirrored by autocorrelation in the hippocampus: autocorrelation significantly decreased when switch rate increased. Most importantly, hippocampal autocorrelation during encoding was positively correlated with temporal clustering during free recall. Collectively, these findings establish a critical link between context representations in the hippocampus and temporal clustering in free recall.

Topic Area: LONG-TERM MEMORY: Episodic