1. Introduction
CORTEX
These authors contributed equally to this work.Experiments show activation of the left dorsolateral prefrontal cortex (DLPFC) in motor imagery (MI) tasks, but its functional role requires further investigation. Here, we address this issue by applying repetitive transcranial magnetic stimulation (rTMS) to the left DLPFC and evaluating its effect on brain activity and the latency of MI response. This is a randomized, sham-controlled EEG study. Participants were randomly assigned to receive sham (15 subjects) or real high-frequency rTMS (15 subjects). We performed EEG sensor-level, source-level, and connectivity analyses to evaluate the rTMS effects. We revealed that excitatory stimulation of the left DLPFC increases theta-band power in the right precuneus (PrecuneusR) via the functional connectivity between them. The precuneus theta-band power negatively correlates with the latency of the MI response, so the rTMS speeds up the responses in 50% of participants. We suppose that posterior theta-band power reflects attention modulation of sensory processing; therefore, high power may indicate attentive processing and cause faster responses.Motor imagery (MI) is defined as the mental simulation of a given movement in working memory without any overt motor output [Neuroimaging studies reveal that MI consistently recruits a network of bilateral premotor (supplementary motor areas, the dorsal and ventral premotor cortices, the cingulate and putamen), rostral inferior and middle superior parietal (the inferior and superior parietal lobules), basal ganglia, and cerebellar regions [A recent meta-analysis identified the involvement of the left dorsolateral prefrontal cortex (DLPFC) in MI rather than in movement execution or motor observation [In line with these hypotheses, numerous studies have shown a greater involvement of DLPFC in MI than in motor execution [Transcranial magnetic stimulation (TMS) is a non-invasive technique that uses magnetic fields to stimulate specific regions of the brain. TMS allows for the direct modulation of neural activity in targeted brain regions, providing insights into their causal role in cognitive processes [The mentioned studies, among many others, highlight the utility of TMS in elucidating the causal role of specific brain areas during MI. However, it is worth noting that the interpretation of TMS results requires careful consideration, and additional research is often necessary to fully understand the complex interplay of brain networks involved in cognitive processes. Particularly, the functional role of the DLPFC in MI tasks requires further investigation.The present study aimed to investigate the functional contribution of the left DLPFC to the MI using transcranial magnetic stimulation (TMS). We applied a single session of high-frequency repetitive TMS (rTMS) to the left DLPFC before healthy subjects started MI tasks. We hypothesized that rTMS would alter neurophysiological correlates of MI (e.g., the characteristics of EEG event-related desynchronization (ERD) [