Intracortical excitability after repetitive hand movements is differentially affected in cortical versus subcortical strokes.

Repetitive training of isolated movements induces reorganization of motor cortical representations. To elucidate the mechanisms of practice-dependent cortical plasticity within the lesioned central motor system at the time of the application of a therapeutic intervention, we examined the effect of repetitive movements on intracortical facilitation (ICF) and inhibition of agonist (extensor carpi radialis [ECR]) and antagonist (flexor carpi ulnaris) muscles of the hand shortly after the movements, by the paired-pulse technique in patients with cortical (n = 9) and subcortical strokes (n = 11). Short intracortical inhibition and ICF were studied by using interstimulus intervals of 2 and 8 milliseconds, respectively, and their interaction with active or passive movement.

Selective effect of repetitive hand movements on intracortical excitability.

Repetitive training of isolated movements induces local reorganization of the motor cortex. To investigate the effect of repetitive movements on intracortical inhibition and facilitation shortly after the movements, we performed paired-pulse transcranial magnetic stimulation in 12 healthy subjects by using interstimulus intervals of 2 and 8 ms, respectively. Motor evoked potentials (MEPs) were recorded simultaneously from the extensor carpi radialis (ECR) and the flexor carpi ulnaris muscle (FCU) following paired stimuli at rest or 1 s after repetitive (every 6 s) active or passive wrist extensions and compared with MEPs produced by single stimuli at rest.

Influence of repetitive hand movements on intracortical inhibition.

Repetitive movements have been reported to induce task-specific changes of intracortical inhibition and facilitation, but the mechanism operating shortly after hand movement is unclear. Transcranial magnetic single and paired stimuli (2 ms) were applied to 15 healthy subjects at rest and 1 s after repetitive (every 6 s) active and passive hand extensions. Motor evoked potentials (MEPs) were recorded from hand extensors (agonists) and flexors (antagonists).

Cortical neuromagnetic fields evoked by voluntary and passive hand movements in healthy adults.

Neuromagnetic fields were recorded from the left cerebral hemisphere of six healthy right-handed subjects under three different conditions: (1) externally triggered rapid voluntary extension and flexion of the right hand, (2) passive extension and flexion of the right hand, and (3) stimulation of the skin of the right index finger by means of air pressure. Location analysis using the current density analysis did not reveal any differences between motor evoked field I (MEF I) in active and passive movements, and met the maximum of cerebral activation in the contralateral precentral region. In contrast, the sensory evoked field was located clearly in the contralateral postcentral region.