Specific increase of human entorhinal population synaptic and neuronal activity during retrieval

Population transmembrane currents and neuronal firing in different layers of the human entorhinal cortex (ER) were recorded during semantic and episodic memory processes using a linear array of 24 laminar microelectrodes. Both measures, as well as local broadband spectral power, increased during retrieval of newly-learned characteristics, especially in superficial layers. No differences were observed in the activity evoked by remembering people as compared to places. Semantic retrieval evoked similar activity. In contrast, intentional encoding of declarative memory evoked relatively little activity. A double-dissociation of these responses with simultaneously recorded lateral inferotemporal recordings suggests that entorhinal cortex may be specifically engaged during retrieval, across multiple memory types and materials.