Episodic memory processing studied using patient recordings
November 2021
University of Texas Southwestern, Dallas, USA
Episodic memory requires linking objects to a temporal context, a process for which the medial temporal lobe (MTL) is crucial. This study used records from 27 people who underwent surgery for intractable epilepsy. 103 memory-sensitive neurons in the hippocampus and entorhinal cortex were identified, whose firing rates predicted successful encoding of episodic memory while subjects performed a verbal free recall task. These neurons exhibit important properties. First, as predicted by the temporal context model, they show recovery of firing patterns observed during encoding at the time of retrieval. The extent of retrieval predicted the tendency of subjects to group the retrieved memory items according to the serial position of the input. In addition, it was found that the spiking activity of these neurons was tied to the phase of hippocampal theta oscillations, but that the middle phase of spiking activity shifted between encoding and retrieval of memories. This unique observation is consistent with the predictions of the Separate Phases at Encoding And Retrieval (SPEAR) model. Taken together, the properties of memory-sensitive neurons characterize direct electrophysiological mechanisms for the representation of contextual information in human MTL.
Neurons in the human medial temporal lobe track multiple temporal contexts during episodic memory processing
Bradley Lega
Added on: 02-01-2022
[1] https://www.sciencedirect.com/science/article/pii/S1053811921009629?via%3dihub=&emci=ba5115d1-af5e-ec11-94f6-0050f2e65e9b&emdi=67c90150-b661-ec11-94f6-0050f2e65e9b&ceid=2015591
