Hippocampal ripple and its interaction with neocortex support successful visual short-term memory
Xianhui He1 (firstname.lastname@example.org), Jing Liu2, Ying Cai1; 1Zhejiang Univeristy, 2The Hong Kong Polytechnic University
Hippocampal ripple activity, a highly synchronized neural oscillations generated by local neuronal assemblies (70-180 Hz), has been indicated as playing a critical role in human episodic memory. Nonetheless, how the hippocampal ripple and its interaction with neocortex supports visual short-term memory (VSTM) remains far from clear. The current study investigated the intracranial electroencephalogram (iEEG) recordings of both the hippocampus (HPC) and lateral temporal lobe (LTL) from 14 epilepsy patients during a delayed matching to sample task with naturistic objects as stimuli. The results revealed that hippocampal ripple rates dynamically changed across different VSTM stages. Specifically, hippocampal ripple rates increased during early encoding, ramping up during maintenance, and persistently rising until VSTM responses were made. Importantly, greater ramping-up of hippocampal ripple rates during maintenance predicted successful VSTM memory while higher ripple rates during retrieval predicted faster response times. Moreover, these hippocampal ripples were coupled to the LTL ripples with higher probabilities of LTL ripples occurring around hippocampal ripples (i.e., HPC-LTL co-rippling), showing a similar ramping up during maintenance, especially among remembered trials. Similarly, greater HPC-LTL co-rippling during VSTM retrieval predicted faster response time. Further ripple-locked multivariate decoding analysis based on broadband spectral power revealed that both hippocampal ripples and LTL ripples were associated with memory representational reinstatement during all VSTM stages. All the above-mentioned results were corrected for multiple comparisons. Taken together, our preliminary findings suggested that dynamically changed hippocampal ripple activity, coupled with LTL ripples, coordinates the reinstatement of memory representations in supporting successful VSTM.
Topic Area: EXECUTIVE PROCESSES: Working memory
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April 13–16 | 2024