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.

Inclusion Criteria:

• amnestic and amnestic plus MCI-patients:

  1. Concern reflecting a change in cognition reported by patient or informant or clinician (i.e., historical or observed evidence of decline over time)
  2. Objective evidence of memory impairment; additional cognitive domains may be affected as well;
  3. Preservation of independence in functional abilities
  4. 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