TY - JOUR T1 - The effects of a TMS double perturbation to a cortical network JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0188-19.2019 SP - ENEURO.0188-19.2019 AU - Ian G.M. Cameron AU - Andreea L. Cretu AU - Femke Struik AU - Ivan Toni Y1 - 2020/01/10 UR - http://www.eneuro.org/content/early/2020/01/10/ENEURO.0188-19.2019.abstract N2 - Transcranial magnetic stimulation (TMS) is often used to understand the function of individual brain regions, but this ignores the fact that TMS may affect network-level rather than nodal-level processes. We examine the effects of a double perturbation to two frontoparietal network nodes, as compared to the effects of single lesions to either node. We hypothesized that Bayesian evidence for the absence of effects that build upon one another indicates that a single perturbation is consequential to network-level processes. Twenty-three humans performed pro- (look towards) and anti- (look away) saccades after receiving continuous theta-burst stimulation (cTBS) to right frontal eye fields (FEF), dorsolateral prefrontal cortex (DLPFC) or somatosensory cortex (S1) (the control region). On a subset of trials, a TMS pulse was applied to right posterior parietal cortex (PPC). FEF, DLPFC and PPC are important frontoparietal network nodes for generating anti-saccades. Bayesian T-tests were used to test hypotheses for enhanced double perturbation effects (cTBS plus TMS pulse) on saccade behaviors, against the alternative hypothesis that double perturbation effects to a network are not greater than single perturbation effects. In one case, we observed strong evidence (BF10 = 325) that PPC TMS following DLPFC cTBS enhanced impairments in ipsilateral anti-saccade amplitudes over DLPFC cTBS alone, and not over the effect of the PPC pulse alone (BF10 = 0.75), suggesting double perturbation effects do not augment one another. Rather, this suggests that computations are distributed across the network, and in some cases there can be compensation for cTBS perturbations.Significance Statement We explore whether a frontoparietal network important to executive control, attentional processing, and saccadic gaze behaviors operates in a distributed fashion, as compared to what would be predicted from combining contributions from individual brain regions. This is important as lesions or perturbations to these regions individually can produce behavioral deficits. We apply inhibitory Transcranial Magnetic Stimulation (TMS) to a frontal cortical region, followed by a second TMS perturbation to a parietal region. The point is that this second perturbation could, in principle, build upon the effects of the first perturbation. We tested different hypotheses regarding the effects of such double perturbations, and conclude that the effects do not build upon one another, suggesting a single perturbation affects a network-level process. ER -