The action potentials of internal and external rectus muscles of a man were induced during a slow horizontal movement of the eye, and the behavior of a single motor unit were investigated by observing its discharge intervals.
1. During a horizontal movement of the eye, discharge intervals of a single unit in the agonist as a rule, decreased, and those in the antagonist increased, but the behavior of each unit varied so much.
2. A striking fact is that some units were often observed discharging with rather constant and high frequencies, regardless of the movement of the eye.
3. Each unit of the internal and of the external rectus muscle had its own range of action fixed to the movement of the eye.
4. The difference between the impulsive and the gliding movement did not always appear in the behavior of each single unit.
5) In the extremest movement of the eye out of the muscle field, the activity of the antagonistic muscle never fell off to zero.
6. Moreover, a few units in the antagonistic muscle were sometimes observed to increase its rate of discharge in the same movement.
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