P193 Effect of transcranial direct current stimulation (tDCS) on sleep-dependent memory consolidation in healthy young subjects

Transcranial direct current stimulation (tDCS) is a method to stimulate the brain in a noninvasive manner leading either to an increased (anodal stimulation) or a decreased (cathodal stimulation) excitability of cortical neurons. Slow oscillations with a frequency below 1 Hz are assumed to be associated with sleep-dependent consolidation of declarative memories by exerting a temporal synchronizing influence on hippocampal reactivations and thalamic spindle activity. Many studies have revealed that offline consolidation during sleep varies with age showing better performances in the young compared to the elderly. A study in young subjects provided evidence of a beneficial impact of an anodal slow oscillation tDCS (0.75 Hz) during early SWS-rich on declarative memory but not on procedural memory. These results could not be confirmed in a study on elderly subjects (Eggert et al., 2013). The present study aims to replicate the results, which have been observed in younger subjects (Marshal et al., 2006). To be able to test an effect of 0.65 with a power of 0.8 and a double-sided alpha 2 ) is triggered after the first 8 consecutive epochs of NREM sleep 2 immediately before the first occurrence of slow wave sleep. The total 25 ′ 8 ″ stimulation period is divided into five 5 ′ 16 ″ intervals, each of them followed by 1 min break without stimulation. To test for a stimulation-dependent effect on offline consolidation during sleep a declarative memory task (word pair test) and a procedural memory task (finger-tapping) have to be completed before sleep and after awakening. Furthermore, sleep stages were scored and EEG power and spindle densities were computed. Statistical analysis was based upon comparisons between the tDCS and the sham stimulation condition. Currently 18 subjects (10 males and 8 females) are already enrolled. First results will be presented at the meeting.