Investigating the effects of cortico-cortico paired associative stimulation on motor control

Transcallosal projections extend through the corpus callosum and facilitate communication between right and left hemispheres, a critical function for many coordinated unimanual and bimanual movements. Transcallosal circuits are linked to impaired movement in clinical populations, making the circuit a valuable target for neuromodulation. Cortico-cortico paired associative stimulation (cc-PAS) is an emerging dual-site transcranial magnetic stimulation (TMS) technique in which pairs of pulses are delivered to two connected cortical areas to modulate brain function. In previous research, cc-PAS has been shown to influence corticospinal excitability, and reaction time of the first dorsal interosseous (FDI) muscle (Rizzo et al., 2009), demonstrating the ability to elicit behavioural changes. This study aimed to examine the effect of cc-PAS on movement kinematics using the KINARM end point lab. Thirty healthy young adults attended two sessions, separated by a minimum of one week apart. During one session, cc-PAS was administered over the FDI muscle representation of both motor cortices. Cc-PAS consisted of 180 pairs of pulses delivered 10ms apart, with the first pulse of the pair delivered over the right M1. During the other visit, participants contracted their left FDI during the delivery of cc-PAS to determine if the addition of a physiological stimulus would modulate motor control. Participants completed a visually guided and reverse visually guided reaching task before and after the intervention. Results suggest whole limb movement kinematics may be altered by cc-PAS during the addition of a physiological stimulus.