Modulation of Memory Consolidation in Humans

University Medicine Greifswald

Status: Completed

Conditions: Sleep

Treatments: Other: Device: no stimulation; Other: Device: anodal tDCS

Study type: Interventional

Funder types: Other

Identifiers

NCT04714879

MemorySFB

Details and patient eligibility

About

The goal of the present study is to optimize effects of slow oscillatory transcranial direct current stimulation (so-tDCS) on sleep physiology and memory consolidation in humans by combining computational and experimental human models in an iterative process. The investigator therefore works in cooperation with Prof. Dr. Klaus Obermayer (TU Berlin), who contributes computation models with the aim to mechanistically understand the impact of different perturbations on sleep-related electrophysiological features, and to subsequently optimize so-tDCS parameters for inducing SO and spindle activity.

Full description

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.

Enrollment: 54 patients

Sex: All

Ages: 50 to 80 years old

Volunteers: Accepts Healthy Volunteers

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.

Trial design

Primary purpose: Other

Allocation: Randomized

Interventional model: Crossover Assignment

Masking: Double Blind

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54 participants in 2 patient groups

Slow oscillating transcranial direct current stimulation (so-tDCS)

Experimental group

Description:

7 experimental daytime naps with so-tDCS of different frequencies (fixed frequency of 0.75 Hz versus individually adapted frequency) and durations (5 min, 2 min, 30 sec) (Crossover assignment, applicable for each participant)

Treatment:

Other: Device: anodal tDCS

Sham stimulation

Sham Comparator group

Description:

sham so-tDCS during a daytime nap (Crossover assignment, applicable for each participant)

Treatment:

Other: Device: no stimulation