Temporal aspects of passive movement-related corticomotor inhibition

We have previously shown that during rhythmic passive movement of the index finger, the amplitude of the motor evoke potential (MEP) of the first dorsal interosseous muscle (FDI) as the index finger moved through mid-range adduction, is significantly reduced compared to rest [Edwards, D. J., Thickbroom, G. W., Byrnes, M. L., Ghosh, S., & Mastaglia, F. L. (2002). Reduced corticomotor excitability with passive movement: A study using Transcranial Magnetic Stimulation. Human Movement Science 21, 533-540]. In the present study we have investigated the time-course of this phenomenon. We found that MEP amplitude was significantly reduced at the mid-range position in the first cycle of movement (50+/-6% of resting baseline values), and did not vary across subsequent cycles (10 cycles in 50 s), but that MEP amplitude returned to baseline values within 1s of cessation of movement. The results suggest that the pattern of afferent discharge set up by the kinematics of the movement acting at spinal or supraspinal levels underlies the inhibition observed, rather than an effect of central origin or a cumulative effect of ongoing cyclic movement.     

Reduced corticomotor excitability with cyclic passive movement: a study using transcranial magnetic stimulation

Human voluntary movement involves the integration of kinaesthetic information with efferent motor activity during the planning and execution stages of movement. While much is known of the inhibitory and excitatory effects resulting from activation of specific kinaesthetic sensory receptors, in the present study we employed cyclic passive movement of the index finger in order to activate a range of kinaesthetic receptors in a manner that was intended to correspond to how these receptors might be active during a comparable voluntary movement. We intended to identify how this passive movement protocol might affect the excitability of the corticomotor pathway. During 1 Hz cyclic passive movement of the index finger there was an approximately 60% reduction in the amplitude of the motor evoked response from the first dorsal interosseous muscle. The results of the present study demonstrate that passive movement can have a profound effect on the excitability of the corticomotor pathway.