NSF-BSF: Linking theta with offline memory consolidation: A bridge from wake to sleep

The project will transform the way consolidation can be studied, focusing on spatial memory, a type of memory of great ecological importance and a prime example of memory that depends on storage- evolution involving cortex and hippocampus. Participants learn the specific locations of a set of visual objects displayed on a screen. The ability to recall these locations is precisely quantified immediately after learning and after various delays as forgetting ensues. Memory storage is manipulated during intermediate periods prior to a final memory test. An innovative combination of manipulations is used in a manner that allows for both the repeated replication of findings and the convergence of results from different neuroscientific methods for altering brain function. One manipulation involves partial information to cue retrieval--keys jingling. Whereas the critical to-be-remembered information is spatial-- where the keys are located--spatial memory retrieval can be evoked by presenting just the sound. Memory reactivation produced in this way improves spatial recall. Memory reactivation may also be provoked using electromagnetic stimulation or sensory entrainment at the frequency of theta EEG oscillations. New knowledge will be gained about brain activity at the time of this memory reactivation using EEG and fMRI measurements. To avoid over-reliance on correlational findings (inadequate for establishing causal connections), the experimental manipulations will directly upregulate theta and/or directly promote memory reactivation. The experiments will thus provide new knowledge linking consolidation with brain activity, particularly brain oscillations in the theta band and hippocampal connectivity, thus helping to identify the brain mechanisms required to recall accurate spatial information after a delay. By extension, this research sheds light on the mechanisms that are generally needed for securing new factual and event information so that it can be available when needed.