FUNCTIONS OF HUMAN MUSCLE-SPINDLES IN HAND MUSCLES AS ANALYZED WITH MICRONEUROGRAPHY

While human subjects performed voluntary movements with varying precis ion demands, the normal traffic of impulses originating in spindle aff erents from finger muscles was recorded. Movements that demanded highe r precision resulted in higher impulse rates, indicating stronger fusi motor activity, However, this was regularly associated with stronger c ontractions of the parent muscle, indicating joint increase of skeleto motor and fusimotor activities. This contrasts with recordings from be having cats where gamma independence has been emphasized. The discrepa ncy may be related to the different functional roles ascribed to cat h ind limb muscles and human hand muscles, and related differences in ne ural control circuits design in the two.