Abstract
The brain at rest exhibits a spatio-temporally rich dynamics which adheres to systematic behaviours that persist in task paradigms but appear altered in disease. Despite this hypothesis, many rest state paradigms do not act directly upon the rest state and therefore cannot confirm hypotheses about its mechanisms. To address this challenge, we combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) to study brain’s relaxation toward rest following a transient perturbation. Specifically, TMS targeted either the medial prefrontal cortex (MPFC), i.e. part of the Default Mode Network (DMN) or the superior parietal lobule (SPL), involved in the Dorsal Attention Network. TMS was triggered by a given brain state, namely an increase in occipital alpha rhythm power. Following the initial TMS-Evoked Potential, TMS at MPFC enhances the induced occipital alpha rhythm, called Event Related Synchronisation, with a longer transient lifetime than TMS at SPL, and a higher amplitude. Our findings show a strong coupling between MPFC and the occipital alpha power. Although the rest state is organized around a core of resting state networks, the DMN functionally takes a special role among these resting state networks.
Highlights
The existence of Resting State Networks (RSNs) is clearly established[1,2,3,4]
We found that the occipital alpha power before transcranial magnetic stimulation (TMS) was not significantly different between both conditions (p > 0.05; mean ±standard deviation; medial prefrontal cortex (MPFC): 1.45e-10 ± 4.53e-11; superior parietal lobule (SPL): 1.52e-10 ± 5.27e-11)
The alpha power was averaged for each subject in this time window
Summary
The existence of Resting State Networks (RSNs) is clearly established[1,2,3,4]. When human beings stay motionless without falling asleep and let their thoughts run freely without engaging in any task, such as attention[5,6], perception[7,8] or action[9], a consistent network organization, i.e. well-organized spatiotemporal pattern, is observed in brain activation signals[10,11,12,13,14]. We compared the occipital alpha power (at the source level) for both stimulated sites (conditions) during the time period prior to the TMS (referred to as pre-TMS baseline; t =−0.4 to −0.1 s).
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have