Electrophysiological and anatomical estimation of the number of motor units in the monkey extensor digitorum brevis muscle.

The electrophysiological technique used to estimate the number of motor units in man (McComas et al., 1971b) was tested in six monkeys. The number of motor units was estimated electrophysiologically in the extensor digitorum brevis (EDB) after deafferentation by excision of the lumbo-sacral dorsal root ganglia. In five animals, the mean number of motor units obtained by the technique was in good agreement with the number of alpha motor fibres counted in the nerve to EDB. However, the results obtained in one animal with partial denervation of the EDB indicate that the technique might be unreliable, at least at certain stages, after a peripheral nerve lesion.