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Lorella Battelli, Ela Plow, Emily Grossman; Local Immediate Versus Long-Range Delayed Impact Of rTMS On The Visual Attention Network. Journal of Vision 2016;16(12):607. doi: https://doi.org/10.1167/16.12.607.
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Long-lasting, maladaptive interhemispheric imbalance is hypothesized to be the basis of sustained attention deficits in chronic phase of stroke, which are readily identified during bilateral visual tracking (Battelli et al., 2009). In a test of the causal role of interhemispheric imbalance in chronic stroke, Agosta et al. (2014) improved visual tracking in chronic right parietal patients with 1Hz offline inhibitory rTMS to the healthy left parietal cortex, re-establishing the interhemispheric balance. In that study, behavioral improvements peaked 30 minutes following stimulation. In this study, we measure the timecourse of cortical reorganization following rTMS over left parietal cortex in healthy individuals engaged in visual tracking. Method. Subjects engaged in a visual tracking task following offline, inhibitory rTMS or sham (conducted on 2 separate days in a counter-balanced order). fMRI data collection was initiated within four minutes from completion of rTMS/sham, with subjects engaged in tracking during four 12 minute scans. We computed functional connectivity (FC) between three nodes of the attention network engaged by visual tracking: the intraparietal sulcus (IPS), frontal eye fields (FEF) and human MT+ (hMT+). Results. rTMS immediately and significantly decreased FC between the stimulation site (left IPS) and all other regions, and FC recovered to normal levels within 30 minutes. rTMS caused increases in FC between left and right FEF at approximately 36 min following stimulation, and between sites in the unstimulated hemisphere approximately 48 min after stimulation. Conclusion. rTMS has immediate impact on functional connectivity directly under the stimulation site, and substantially delayed effects remotely. These findings are consistent with rTMS over left IPS inducing interhemispheric imbalances throughout the healthy brain during visual tracking (Plow et al., 2014) and delayed changes in the FEF following theta burst stimulation during a saccade task (Hubl, 2006).
Meeting abstract presented at VSS 2016
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