Memory Reactivation with Neurostimulation during Sleep Elicits Electrophysiological Responses that Predict Behavioral Changes
Ryan J. Hubbard1, Nicholas A. Ketz1, Aaron P. Jones2, Bradley Robert2, Natalie B. Bryant2, Steven W. Skorheim1, Shane Roach1, Vincent P. Clark2, Praveen K. Pilly1; 1Information and Systems Sciences Laboratory, HRL Laboratories, LLC, Malibu, CA, 2The University of New Mexico, Albuquerque, NM
Slow-wave sleep (SWS) plays an important role in memory consolidation, as neural patterns of memory related activity are reactivated during UP states of the ongoing slow oscillations. Previous work has demonstrated that reactivations can be induced by presenting encoding-related cues, such as sounds or odors, during sleep. Here, we utilized transcranial current stimulation (tCS) to reactivate memories, and assessed neurophysiological changes during sleep associated with later performance in a virtual reality-based declarative memory task. During encoding of events, subjects received unique Spatio-Temporal Amplitude Modulated Patterns (STAMPs) of tCS currents, which were later re-applied specifically during UP states of SWS to cue memory reactivation. We analyzed significant changes in spectral power in specific frequency bands across 32 channels of the scalp EEG following stimulation events, and compared to separate sham data in which no stimulation was applied within subjects. We then employed cluster-based permutation statistics to quantitatively examine the significant differences between stim and sham power changes that were correlated with overnight behavioral performance changes on two consecutive nights. STAMPs led to modulations in power across several frequency bands, but only certain clusters were predictive of episodic recall changes. Namely, we identified spatiotemporal clusters in the theta (4-8 Hz), alpha (8-12 Hz), and beta (16-30 Hz) frequency bands in which EEG power significantly correlated with behavior. These results provide further insight into the neural processes related to successful memory consolidation during sleep.
Topic Area: LONG-TERM MEMORY: Episodic