The beneficial effect of nocturnal sleep on memory consolidation is well-documented in young, healthy subjects. Especially, periods rich in slow-wave sleep (SWS) have shown a memory enhancing effect on hippocampus-dependent declarative memory. Slow oscillatory activity typically occuring during SWS has been implicated in the consolidation effect. Recent evidence in young healthy subjects suggest that the sleep-associated consolidation effect can be amplified by the application of a weak transcranial oscillatory electric current within the frequency range of SWS in humans (0,7-0,8 Hz) during SWS. If elderly, healthy subjects benefit from transcranial slow oscillatory stimulation (tSOS) during nocturnal sleep as well has not been studied so far. The primary aim of the present study is to investigate the influence of a weak slow oscillating brain stimulation (tSOS) on declarative memory consolidation applied during periods of nocturnal SWS in elderly healthy subjects.

Inclusion Criteria:

• elederly, healthy Subjects
• unobtrusive, neuropsychological screening
• age: 50-90 years
• right handed

Exclusion Criteria:

• untreated severe internal or psychiatric diseases
• epilepsy
• other severe neurological diseases eg., previous major stroke, brain tumour, dementia
• contraindications to MRI