Min-Fang Kuo

Abstract Slow oscillatory activity during non-rapid-eye-movement (NREM) sleep plays a crucial role in both physical health and cognitive functions. Enhancing slow oscillatory activity during sleep has the potential to benefit these domains, yet an optimal stimulation protocol has not been established.

Highlights • Anodal tDCS with three intensities and durations was applied over the primary motor cortex of healthy older adults. • All active stimulation conditions resulted in a significant enhancement of motor cortical excitability in two age groups. • We observed prolonged plasticity for two protocols with the highest stimulation intensity (i.e., 3 mA-20 min, 3 mA-30 min). • The facilitatory aftereffects of anodal tDCS did not significantly differ between the age groups.

Highlights • With single session stimulation, both, standard and intensified protocols induced E-LTP-like plasticity. • Short-interval repetition resulted in L-LTP-like plasticity for the standard, but not the intensified tDCS protocol. • A repetition interval of 3 h did not induce L-LTP-like plasticity for standard and intensified protocols.