Title : The role of local spindles in memory consolidation
Abstract:
Background: Strong evidence shows that sleep beneficially impacts memory, but how this benefit is produced within the brain’s neuronal networks remains unclear. Recently, local spindles have been distinguished from global spindles. Local spindle interactions with global spindles, slow oscillations, and hippocampal activity in memory consolidation has yet to be explored.
Objective: The primary objective of this study is to examine the functional role of locally confined sleep spindles in memory consolidation. Sleep spindles are transient bursts of ~11-16 Hz oscillations in the electroencephalogram (EEG) that arise during non-rapid eye movement (NREM) sleep. More broadly, we hope to utilize our findings in this study to better understand the mechanism of memory consolidation during sleep and further determine more effective sleep interventions to improve memory in health and disease. Our hypothesis is that local spindles play a role in memory consolidation that is complementary to the role of global spindles. For example, they may occur selectively in the cortical areas most strongly involved with a particular memory.
Specific Aims: In Aim 1, we seek to determine the role of local sleep spindles in procedural memory consolidation using auditory cue-induced memory reactivation. In Aim 2, we will seek to determine the role of local sleep spindles in declarative memory consolidation using auditory cue-induced memory reactivation.
Methods: We will recruit 17 epileptic patients undergoing invasive monitoring with intracranial depth electrodes at Carilion Roanoke Memorial Hospital. We will make human intracranial recordings during two NREM sleep-dependent tasks, one a declarative memory task and the other a procedural memory task. Each task will be performed on separate nights and before sleeping. Half of the subjects will perform the declarative memory task first and the other half will perform the procedural memory task first. A subset of sounds will be played as auditory cues while the patient sleeps and sleep data will be recorded. Subjects will be retested after waking up. Performance improvement for each task on retest will be measured and neural dynamics of local spindles will be characterized.
Expected Outcomes: We expect the higher resolution of intracranial electrodes will capture an induction of local spindles during NREM sleep in response to auditory cues that improve memory task performance. Success in this study will provide a detailed understanding of how sleep spindles interact with other primary oscillatory dynamics (including global spindles). Additionally, this will inform the broader effort in developing effective memory consolidating sleep interventions.
