Remembering with high fidelity: Evidence implicating sleep and sleep spindles
Sarah Witkowski1, Jessica Creery1, Leonardo Dionisio1, Ken A. Paller1; 1Northwestern University
Current theories of sleep postulate that memories can be strengthened through replay. This replay is thought to be engaged spontaneously during sleep, and has tentatively been associated with fast sleep spindles in EEG recordings (brief increases in oscillatory activity at 13.5-15 Hz). In this study, we investigated EEG sleep physiology and memory using a difficult object-recognition test and a spatial-recall test. Participants first learned the locations of 64 objects on a grid. Each object was presented with a related sound. After a pre-nap test of this spatial knowledge, participants took a 90-minute nap, and 32 object sounds were presented softly during slow-wave sleep. Upon waking, participants were given a surprise recognition test with 96 objects, including 32 old (seen before), 32 similar (same category as one seen before), and 32 new objects. Participants attempted to identify each object as old, similar, or new, and then took a post-nap spatial recall test. A recognition specificity score was calculated as the sum of correctly recognized old and similar objects from the object-recognition task. Fast spindle density during sleep (spindles per minute) correlated with the specificity score, but not with spatial recall accuracy. Cues during sleep produced a relative improvement for top-half learners in spatial recall, as observed in previous studies of targeted memory reactivation (TMR). Recognition specificity wasn’t influenced by TMR. Overall, these results provide further evidence that fast spindles play a role in memory consolidation during sleep, particularly for memory precision with respect to remembering which specific objects were seen before.
Topic Area: LONG-TERM MEMORY: Episodic