Acute and chronic effects of repeated 1 Hz rTMS on the temporal cortex

Electroencephalography amplitude, phase synchronization, and directionality of phase coupling within and between hemispheres were compared for different frequency components in 27 healthy individuals before and after 5 days of daily 1 Hz repetitive transcranial magnetic stimulation (rTMS), and at 2 weeks after the last session. Instantaneous amplitudes of α (8-13 Hz) and β (13-30 Hz) frequency components were increased after daily rTMS, the effects of which were declining over time, suggesting an adapting response with repeated rTMS sessions. The phase synchronization of electroencephalography increased significantly in the α frequency, especially the upper-α band (11-13 Hz), in both the frontal and the temporal areas, predominantly in the ipsilateral hemisphere. Asymmetric directional interactions of the upper-α band were stronger from the stimulated area to the contralateral hemisphere. No significant differences were found at 2 weeks after rTMS in any of these values. Focal 1 Hz rTMS induces an enhancement in the ipsilateral dominant corticocortical interaction drastically by interhemispheric asymmetric coupling from the stimulated cortical area with an adapting response with repeated sessions. This kind of method can be valuable for possible clinical applications in various neuropsychiatric conditions to study the therapeutic mechanisms of 1 Hz rTMS.