Repetitive Transcranial Magnetic Stimulation changes absolute theta power during cognitive/motor tasks

Repetitive Transcranial Magnetic Stimulation (rTMS) studies are used to test motor imagery hypothesis. Motor Imagery (MI) represents conscious access to contents of movement intention, generally executed unconsciously during motor preparation. The main objective of this study was to investigate electrophysiological changes, which occurred before and after low-frequency rTMS application when we compared three different tasks: execution, action observation and motor imagery of finger movement. We hypothesize that absolute theta power over frontal regions would change between sensorimotor integration tasks and after 1 Hz of rTMS application. Eleven healthy, right-handed volunteers of both sexes (5 males, 6 females; mean age 28 ± 5 years), with no history of psychiatric or neurological disorders, participated in the experiment. After performing the tasks randomly, subjects were submitted to 15 min of low-frequency rTMS applied on Superior Parietal Cortex (SPC) and performed the tasks again. All tasks were executed simultaneously with Eletroencephalography (EEG) signals recording. Our results clarified the specificity of each sub-region during MI activity. Frontopolar cortex presented involvement with motor process and showed main effect for task and moment. Inferior frontal gyrus presented involvement with long-term memory retrieval and showed interaction between task and moment in the left hemisphere while the right hemisphere showed a main effect for task and moment. The lack of the main effect for conditions on the anterior frontal cortex collaborates with the hypothesis that in this region an integrated circuit of performance monitoring exists.