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Sketchpad Series

State-dependent effects of multifocal transcranial magnetic stimulation on paired associative plasticity in the motor network.

Poster Session F - Tuesday, April 1, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Taylor A. Finkelstein¹, Joseph A. Deluisi¹, Taraz G. Lee², James A. Brissenden², Stephen F. Taylor³, Thad A. Polk², Michael Vesia¹; ¹University of Michigan

Transcranial magnetic stimulation (TMS) can modulate cortical excitability and functional connectivity, but its effects depend on the activation state of the targeted brain network. Our previous work has demonstrated that functional interactions between brain regions derived from dual-site TMS are context-dependent. For example, connectivity between the posterior parietal cortex (PPC) and primary motor cortex (M1) shows increases in excitability during action planning but not during rest. Despite this, the influence of behavioral context on TMS-induced plasticity in action control circuits is still unclear. We propose that specific behavioral states during TMS can engage neurons involved in action control and affect TMS-induced plasticity and motor function. This study will deliver precisely timed dual-coil pulses to the PPC and M1 (cortico-cortical paired associative stimulation, cPAS). In this within-subject, counterbalanced design, 20 healthy participants will undergo three cPAS conditions: (1) cPAS during a grasping task, (2) cPAS during rest, and (3) cPAS targeting a parietal region outside the grasping network while performing the grasping task. Electrophysiological (TMS) and manual dexterity measures will be collected to assess changes in plasticity and associated hand function within one hour of each intervention. We expect that behavioral context will modulate the aftereffects of cPAS on motor cortical excitability and motor performance, with state-dependent stimulation leading to selective or enhanced effects on motor function. Constraining the brain state with a behavioral task during TMS could optimize plasticity induction in motor circuits underlying action control, offering a strategy to enhance targeted brain stimulation therapies in neurological disorders like stroke.

Topic Area: PERCEPTION & ACTION: Motor control