Poster D85, Monday, March 27, 8:00 – 10:00 am, Pacific Concourse
Modulation of oscillatory power and connectivity in the human posterior cingulate cortex supports the encoding and retrieval of episodic memories
Bradley Lega1, Michael Rugg2, James Germi1; 1University of Texas-Southwestern Medical Center, 2Universwity of Texas at Dallas
The role of the posterior cingulate cortex in episodic memory has not been described using intracranial EEG. Existing evidence has led researchers to posit that the PCC supports mnemonic processes: it exhibits degeneration in memory disorders, and fMRI investigations have demonstrated memory–related activation during both encoding and retrieval of memory items. Using data gathered from 21 human participants who underwent stereo electroencephalography for seizure localization, we characterized oscillatory patterns in the posterior cingulate cortex during the encoding and retrieval of episodic memories. We describe for the first time a subsequent memory effect during item encoding characterized by increased gamma band oscillatory power and a low frequency power decrease. 14 participants had stereotactic electrodes located simultaneously in the hippocampus and PCC, and with these unique data we describe connectivity changes between these structures that predict successful item encoding and that precede item retrieval. Oscillatory power during retrieval matched the pattern we observed during encoding, with low frequency desynchronization and a gamma band power increase. We discuss our findings in light of existing theories of episodic memory processing, including the information via de–synchronization hypothesis and retrieved context theory, and examine how our data fit with existing theories for the functional role of the PCC. These include a postulated role for the PCC in modulating internally directed attention and for representing or integrating contextual information for memory items.
Topic Area: LONG-TERM MEMORY: Episodic