Effects of Brain Stimulation During a Daytime Nap on Memory Consolidation in Patients With Mild Cognitive Impairment

Effects of Brain Stimulation During a Daytime Nap on Memory Consolidation in Patients With Mild Cognitive Impairment

Impact of Transcranial Slow Oscillating Stimulation on Memory Consolidation During Slow Wave Sleep of a Daytime Nap in Patients With Mild Cognitive Impairment(MCI)

The beneficial effect of nocturnal as well as daytime sleep on memory consolidation is well-documented in young, healthy subjects. Slow wave sleep (SWS), in particular, with its slow oscillating activity have shown to enhance declarative, hippocampus-dependent memory representations. This impact of sleep on memory performance can be additionally enhanced by exogeneous induction of transcranial slow oscillating stimulation (tSOS) within the frequency range of SWS in humans (0,7- 0,8 Hz) during sleep, as has been demonstrated in young, healthy subjects. If patients with amnestic mild cognitive impairment (MCI)- usually characterized by initial difficulties in hippocampus dependent memory functions - benefit from transcranial slow oscillatory stimulation (tSOS) during sleep as well has not been studied so far. The primary goal of the study is therefore to investigate the impact of oscillating current stimulation (tSOS) during a daytime nap on declarative memory consolidation in MCI patients.

mild cognitive impairment, dementia, MCI, brain stimulation, tSOS, tDCS, sleep, nap, daytime sleep, memory, memory consolidation

Retention of declarative memories after 0.75 Hz stimulation during SWS, vs after sham stimulation during SWS

Retention between stimulation conditions (0.75 Hz during SWS, vs sham stimulation during SWS) in the declarative memory task.

Amount of slow wave sleep assessed by standard polysomnographic criteria in 0,75 Hz vs SHAM stimulation during SWS. Spindel activity during sleep indicated via several spindel parameters like number, duration, frequency of spindles; compared between 0,75 Hz and SHAM stimulation during SWS. Neuronal correlates (EEG-power in slow oscillation frequency bands induced by 0,75 Hz vs SHAM stimulation during SWS; EEG-correlates of encoding and retrieval of a declarative memory task). Performance in further memory systems (procedural), compared between 0,75 Hz and SHAM stimulation during SWS.

Inclusion Criteria: amnestic and amnestic plus MCI-patients: Concern reflecting a change in cognition reported by patient or informant or clinician (i.e., historical or observed evidence of decline over time) Objective evidence of memory impairment; additional cognitive domains may be affected as well; Preservation of independence in functional abilities no dementia age: 50-90 years Exclusion Criteria: untreated severe internal or psychiatric diseases epilepsy other severe neurological diseases eg., previous major stroke, brain tumour dementia contraindications to MRI

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