Poster A83, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Self-referential memory and rest activity within the posteromedial cortex originate from different neuronal populations
Amy Daitch1, Josef Parvizi1; 1Stanford University
Brain regions within the default mode network (DMN) are engaged during periods of rest, as well as during goal-directed self-referential processes such as remembering a past event. Given the spatial smoothing inherent to neuroimaging methods, and their limited temporal resolution, it has been difficult to discern if the self-referential memory and resting activity in the DMN originate from the same neuronal populations. We recorded intracranial signals from the posteromedial cortex (PMC), a hub of the DMN, in 14 human subjects, and measured activity from discrete neuronal populations during experimental memory and rest conditions. We replicated our previous findings that PMC sites activated during autobiographical memory retrieval were almost always distinct from those activated during cued rest (Dastjerdi 2011 PNAS; Foster 2012 PNAS; Foster 2015 Neuron), though these two types of neuronal populations were anatomically close (less than 1 cm apart). More importantly, we discovered two distinct patterns of activity during cured rest: Some PMC neuronal populations exhibited fast and transient responses that were time-locked to the rest cue (possibly signaling a switch from non-rest to rest) while others showed delayed and sustained responses during rest condition (possibly reflecting the maintenance of resting state with spontaneous thought). Our findings shed new light on the functional heterogeneity within the PMC at the level of neuronal populations and offer new information about resting activity within the DMN.
Topic Area: LONG-TERM MEMORY: Episodic