(HealthDay News) – A system of paired, noninvasive stimulation of the brain motor cortex and the wrist can temporarily improve voluntary hand movement in patients with spinal cord injury, according to a study published online Nov. 29 in Current Biology.

Karen L. Bunday, PhD, and Monica A. Perez, PhD, from the University of Pittsburgh, tested tailored noninvasive brain and peripheral nerve stimulation protocols on 19 patients with cervical spinal cord injury and 14 age-matched healthy controls. Corticospinal neurons were activated via transcranial magnetic stimulation over the hand representation of the motor cortex, and spinal motoneurons were activated by peripheral nerve stimulation of the ulnar nerve at the level of the wrist.

The researchers found that the paired pulse-stimulation improved voluntary hand movement only if the presynaptic volleys arrived one to two milliseconds before motoneuron discharge. When 100 paired pulses were delivered every 10 seconds for about 20 minutes, corticospinal transmission, index finger force, and electromyographic responses increased for up to 80 minutes. The effect was observed in both injured and healthy individuals, and manual dexterity improved among the participants with spinal cord injury.

“These findings are the first demonstration that spike timing-dependent plasticity of residual corticospinal-motoneuronal synapses provides a mechanism to improve motor function after spinal cord injury,” Bunday and Perez conclude.

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