Poster E73, Monday, March 26, 2:30-4:30 pm, Exhibit Hall C
Mental Chronometry of Episodic Memory Retrieval
Logan J. Fickling1, Michael J. Kahana1; 1University of Pennsylvania
The process of learning, maintaining and later accessing information can be modeled as an ongoing process that blends new information (content) into a gradually drifting context. Several theories of memory search assert that context reinstatement precedes content reinstatement during episodic memory retrieval. In order to test hypothesized neural predictions made by the Context Maintenance and Retrieval Model, we employed a free-recall task in 221 patients with medically resistant epilepsy. Using intracranially recorded high frequency activity (HFA, 95 Hz), thought to be a reflection of general neural activation, we examined the neural dynamics underlying episodic memory retrieval in frontal, temporal, parietal and hippocampal electrodes. In the time course prior to a correct retrieval, we found the relative order of neural HFA activation to start bilaterally hippocampi, followed by left frontal lobe, left parietal lobe, right parietal lobe, right frontal lobe, right temporal lobe, left temporal lobe. Next we examined these interactions on a more spatially restricted scale, using the talairach atlas to further subdivide the brain. We additionally examined how this temporal ordering changed for recalls with inappropriate context or content, intrusions (words recalled from a previous learning list, or never shown before), and exploited neural similarity (correlations of HFA) between encoding and retrieval as a function of lag (positional distance relative to the recalled item) to isolate context and content signals. Our findings contribute to the understanding of episodic memory by characterizing the mental chronometry of correct and incorrect retrievals, and providing further support for context based models of memory.
Topic Area: LONG-TERM MEMORY: Episodic