Modulation of Memory Consolidation in Humans

Sleep plays an active role in long-term consolidation of memories. Specifically, slow oscillations (SO, large amplitude waves <1 Hz) and sleep spindles (8-15 Hz), that can be measured by electroencephalography (EEG), appear to be critical for declarative memories. According to the "active system consolidation" account, newly encoded memories are reactivated during sleep, accompanied by sharp-wave ripple events (80-100 Hz) in the hippocampus, and redistributed to cortical long-term storage networks through a coordinated dialog between the hippocampus and neocortex. This dialog is supposedly mediated by a particular coupling between cortical SO and thalamo-cortical fast spindles (12-15 Hz), with spindles preferably occurring during SO up-phases, and hippocampal ripples grouped at the troughs of fast spindles. Slow spindles (8-12 Hz) are a separate kind of sleep spindle activity whose function in memory consolidation is less well understood.

Interventions targeting sleep parameters may not only make it possible to beneficially modulate a vital aspect of memory consolidation, i. e., sleep-dependent memory consolidation, but may also help to delineate which specific elements of the neural dynamics during sleep are crucial for successful consolidation.

Inclusion criteria

• Adults aged between 50-80 years
• screened as healthy in a structured telephone interview

Exclusion criteria

• Mini Mental Status Examination scores below 24
• history of severe untreated medical, neurological, and psychiatric diseases
• sleep disorders
• alcohol or substance abuse
• brain pathologies identified on MRI scan
• intake of medication acting primarily on the central nervous system (e.g., antipsychotics, antidepressants, benzodiazepines, or any type of over-the-counter sleep-inducing drugs such as valerian),
• nonfluent German language abilities.