Repetitive Transcranial Magnetic Stimulation Increases Phase-Amplitude Coupling

Abstract

A prominent feature of brain activity with relevance to cognitive processes is Phase-Amplitude Coupling (PAC) between slow and fast oscillatory signals. A newly developed neural mass model of cross-frequency coupling [1] predicts, counter-intuitively, that PAC shows sustained increases after repetitive Transcranial Magnetic Stimulation (rTMS). This is because rTMS leads to simultaneous neuronal firing in distinct regions, thereby enhancing the connectivity that, according to the model, is needed for PAC to be increased. We tested this prediction in healthy human volunteers. Two seconds of 10Hz rTMS were applied to the intraparietal sulcus, temporal-parietal junction, and lateral occipital complex. PAC in the subsequent electro-encephalogram was analyzed for two band pairs, theta-gamma and alpha-gamma, and compared to a sham condition. For all stimulation loci, PAC was higher in both band pairs after rTMS than in the sham condition. These results were found to be conform the model prediction. The perspective for using rTMS to modulate cross-band coupling is discussed.