Theta Burst Stimulation alters some but not all critical phenomena in the brain

The brain has been proposed to operate near criticality during wakefulness. The proximity of the system to this critical point, however, can fluctuate during cognitive task and in different neurological disorders (e.g., schizophrenia, depression), reflecting a possible tuning of the system to emphasize certain phenomena (e.g., stability). To more directly explore how criticality affects cognitive processes, neurostimulatory methods are ideal for manipulating cortical dynamics both locally and globally. In this study, we use theta burst stimulation (TBS) to induce changes in phenomena associated with criticality and see if the resting brain can be effectively “pushed” away from the critical state using just neurostimulation. To test resting state dynamics before and after TBS, we record both eyes-open resting state and TMS-evoked responses before and at three time-points post stimulation. We find evidence that TBS affects only one of five measures of criticality. Specifically, cTBS induces an increase in long range temporal correlations in the alpha and delta bands while iTBS induces a slight decrease in the alpha band. Our findings suggest that, like task, TBS modulates some critical phenomena but not others, and underscores the potential of TBS as a tool to directly manipulate criticality in the brain.