Functional magnetic resonance image finding of cortical activation by neuromuscular electrical stimulation on wrist extensor muscles

Objective: To investigate the effects that neuromuscular electrical stimulation on the wrist extensor muscles have on the cerebral cortex. Design: A functional magnetic resonance imaging study was performed on eight normal volunteers. The activation task was the maximum wrist extension by neuromuscular electrical stimulation, applied through a two-channel electrical stimulator. Monophasic square-wave pulses were used. The activation maps were generated by the threshold t test maps. The level of primary motor cortex and primary sensory cortex activations was estimated. Results: Among the eight subjects, seven showed significant activation on contralateral primary sensorimotor cortex by neuromuscular electrical stimulation on the wrist extensor muscles. In these seven subjects, additional bilateral or contralateral supplementary motor area activations were also observed. The number of activated pixels on the primary sensory cortex was slightly greater than that on the primary motor cortex. Conclusion: Neuromuscular electrical stimulation, when applied to the peripheral muscles, seems to have a direct effect on the cerebral cortex.