Electromyographic activity in a distant muscle during simple voluntary movements: an unexpected hand-eye linkage

Supraspinal sensorimotor maps contain adjacent representations of the hand and face. These experiments were designed to determine whether interactions between the representations could be detected at the periphery.

Simultaneous EMG recordings were made from orbicularis oculi and wrist flexor during three conditions, with 50 repetitions each: during exposure to an auditory cue; responding to the auditory cue by wrist flexion; and performing a self-paced wrist flexion in the absence of an auditory cue.

In 8 of 10 healthy volunteers, the rectified, averaged EMGs showed small but consistent increases in orbicularis oculi activity during wrist flexion in the two tasks involving that movement, but not in the auditory task alone.

In one or more of the central sensorimotor maps, voluntary activation of the wrist flexor representation is accompanied by liminal activation of a nearby facial representation which projects to the motoneurons of orbicularis oculi.