Disruption of efference copy signals in fronto-parietal networks with rTMS.

It has been hypothesized that the brain generates efference copy signals for the purpose of predicting the sensory consequences of movement. While research has provided theoretical framework for this process, how motor planning signals are used to determine the spatial configuration of the limbs is unclear. In particular, previous studies have not differentiated between potential contributions of efference copy vs. state estimation signals. In the current experiment, we examined this issue by applying repetitive transcranial magnetic stimulation (rTMS) to candidate sites in the fronto-parietal network to determine how they would influence decisions in a temporal order judgement (TOJ) task under conditions in which bimanual arm crossing movements were performed (moving) or not (stationary). Previous work has shown that under stationary conditions, error rates increase when participants have their arms crossed or are about to cross their arms. In the current study, when the hands were stationary and uncrossed, we observed an increase in TOJ error compared to baseline when rTMS was applied to the posterior parietal cortex (PPC), but not when applied to the dorsal premotor cortex (dPMC). However under moving conditions, error rates were decreased compared to baseline when rTMS was applied to either the dPMC or the PPC. Additionally, targeting a control site (area V4), resulted in no change in TOJ performance. Taken together, this suggests that predictions about the sensory consequences of the spatial configuration of the limbs uses efference copy signals generated in the dPMC and state estimation about the position of the limbs from PPC.  Acknowledgments: This research was supported by the Natural Sciences and Engineering Research Council of Canada.