30. Age related differences in time-varying coupling of EEG oscillations predict connectivity and excitability fluctuations in the Primary Motor Cortex: A TMS-EEG study

Abstract

It has been demonstrated that in young volunteers the characteristics of the ongoing EEG activity immediately preceding a TMS of M1 influence the following MEP amplitude. In this study we explored whether there is an effect of ageing on this EEG-MEP interactions. Then by means of a TMS-EEG experiment, the pre-stimulus EEG characteristics (coherence and spectral profile) of the stimulated M1 were analysed for “high” and “low” MEPs, classified according to the 50th percentile of their amplitude distribution and thus compared in the two groups. On the stimulated hemisphere the EEG coupling was observed more often in the high compared to the low MEP trials in both groups. The coupling in the beta2 band of the stimulated M1 with the ipsilateral prefrontal cortex was able to led to significantly larger MEPs both in young and old subjects. In contrast, the coupling in the delta band of M1 with the ipsilateral parieto-occipital cortices had an effect on the MEP’s size only in young subjects. Moreover, this coupling was significantly higher in elderly brain than in young brain both for high and low MEPs. These data provide evidence for an age-related influence of time-varying synchronization of EEG rhythms in determining M1 excitability.