Modulation of Memory Consolidation in Humans

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.

Study Overview

• Status: Completed
• Conditions: Sleep
• Intervention / Treatment: Other: Device: anodal tDCS; Other: Device: no stimulation

Detailed 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.

• Study Type: Interventional
• Enrollment (Actual): 54
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Germany
  • Greifswald, Germany, 17475
    • University Medicine Greifswald

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 50 years to 80 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Slow oscillating transcranial direct current stimulation (so-tDCS); 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)	Other: Device: anodal tDCS; anodal current modulated by an oscillatory component including a fixed (0,75 Hz) versus individually adapted so-tDCS frequency with three different stimulation durations (5 min, 2 min, 30 sec)
Sham Comparator: Sham stimulation; sham so-tDCS during a daytime nap (Crossover assignment, applicable for each participant)	Other: Device: no stimulation; sham stimulation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in EEG power (μV²) of the slow oscillation frequency band (0.5-1 Hz) following so-tDCS during sleep	Investigation whether 7 different protocols of anodal tDCS (including SHAM) lead to distinct changes in slow oscillation power	up to 20 weeks
Changes in EEG power (μV²) of the sleep spindles frequency band (12-15 Hz) following so-tDCS during sleep	Investigation whether 7 different protocols of anodal tDCS (including SHAM) lead to distinct changes in sleep spindle power	up to 20 weeks
Changes in cross-frequency coupling (resultant vector length) between slow oscillations and sleep spindles following so-tDCS during sleep	Investigation whether 7 different protocols of anodal tDCS (including SHAM) lead to distinct changes in coupling between slow oscillations and sleep spindles	up to 20 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sleep architecture	Proportion of time spent in different sleep stages (in %) during the entire nap and following so-tDCS	up to 20 weeks
Changes in EEG power (μV²) of the delta frequency band (1-4 Hz) following so-tDCS during sleep	Investigation whether 7 different protocols of anodal tDCS (including SHAM) lead to distinct changes in delta power	up to 20 weeks

Collaborators and Investigators

• Sponsor: University Medicine Greifswald
• Collaborators: Technische Universität Berlin
• Investigators: Study Director: Agnes Floeel, Prof., University Medicine Greifswald

Publications and helpful links

General Publications

• Ladenbauer J, Khakimova L, Malinowski R, Obst D, Tonnies E, Antonenko D, Obermayer K, Hanna J, Floel A. Towards Optimization of Oscillatory Stimulation During Sleep. Neuromodulation. 2023 Dec;26(8):1592-1601. doi: 10.1016/j.neurom.2022.05.006. Epub 2022 Aug 16.

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2018
• Primary Completion (Actual): January 5, 2021
• Study Completion (Actual): January 31, 2021

Study Registration Dates

• First Submitted: December 14, 2018
• First Submitted That Met QC Criteria: January 15, 2021
• First Posted (Actual): January 19, 2021

Study Record Updates

• Last Update Posted (Actual): June 11, 2024
• Last Update Submitted That Met QC Criteria: June 10, 2024
• Last Verified: June 1, 2024

More Information

Terms related to this study

• Keywords: memory consolidation
• Other Study ID Numbers: MemorySFB

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No