Klinische Neurophysiologie 2014; 45 - V26
DOI: 10.1055/s-0034-1371205

Differential behavioural and physiological effects of anodal transcranial direct current stimulation in healthy adults of younger and older age

KF Heise 1, M Niehoff 1, JF Feldheim 1, G Liuzzi 1, 2, C Gerloff 1, F Hummel 1
  • 1Universitätsklinikum Hamburg-Eppendorf, Labor für funktionelle Bildgebung und Neurostimulation, Hamburg, Deutschland
  • 2Universitätsspital Zürich, Klinik für Neurologie, Zürich, Schweiz

Purpose: γ-amino-butric acid (GABA)-mediated inhibition has been proposed to constitute a potential target of anodal transcranial direct current stimulation (atDCS). This could be an interesting option to potentially target conditions marked by deficient inhibitory activity as shown for healthy aging. Therefore, the aim of the present work was to analyse the effect of atDCS on resting-state and event-related inhibition and its association with stimulation-induced change in motor behaviour.

Methods: After-effects of a single session of atDCS on resting-state and event-related short-interval intracortical inhibition (SICI) measured with double-pulse TMS and dexterous manual behaviour were examined using a double-blind sham-controlled cross-over design in older (N = 16, age range 65 – 83) and younger (N = 16, age range 22 – 28) healthy participants. Measurement of electrophysiological and behavioural parameters was performed before, immediately after, 45, and 90 minutes after stimulation.

Results: The atDCS effect on resting-state inhibition diverged between age groups in direction, magnitude and timing, i.e. late relative release of inhibition in the younger and early relative increase in inhibition in the older. More pronounced release of event-related inhibition was exclusively seen in the older after atDCS. Baseline event-related modulation of inhibition predicted the magnitude of atDCS-induced effects on resting-state inhibition, i.e. older participants with high modulatory capacity showed a disinhibitory effect comparable to the younger. In accordance with previous data, beneficial effects on behaviour were seen in the older and in tasks requiring higher dexterity; no clear association with physiological changes was found.

Conclusion: Differential effects of atDCS on GABAA-ergic inhibition in older and younger might indicate the distinction of causal mechanisms depending on the functional integrity of the underlying neural network. A physiologically “young” motor network with high modulatory capacity is more likely to show a disinhibitory effect of atDCS. These results favour the individually tailored application of tDCS with respect to specific target groups.