REDUCTION OF ROSTRAL DORSAL ACCESSORY OLIVE RESPONSES DURING REACHING.
K. M. Horn, P. L. E. van Kan, A.R. Gibson.
Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona
APStracts 3:0170N, 1996.
SUMMARY AND CONCLUSIONS
1. Rostral dorsal accessory olive (rDAO) neurons are sensitive to light touch
but have little or no discharge during active movement. We hypothesize that
sensitivity of the rDAO is reduced during movement. To test this hypothesis,
sensitivity of rDAO neurons was evaluated as cats reached out and retrieved a
handle. On selected trials, mechanical or electrical perturbations to the
forelimb were presented, and responses of rDAO neurons to the disturbances
were recorded. 2. All rDAO units were highly sensitive to somatosensory
stimuli during periods of stance. The cells responded to stimuli such as touch
to hairs or light taps to the platform upon which the cat was standing. 3.
Discharges of rDAO neurons showed little or no synchronization to any aspect
of the reaching task. Rostral DAO neurons failed to fire to mechanical
perturbations of the food handle during retrieval or hold phases of the task,
even when their receptive fields included the surface of the paw in contact
with the handle. 4. Electrical stimulation of the skin produced the greatest
evoked response at all rDAO recording sites when the cats were at stance.
Stimulation at any time during the reaching task, including periods of holding
and licking, produced lower amplitude evoked responses. The reduction in
evoked response could be large and was restricted to the limb performing the
task. 5. The data support the hypothesis that the cutaneous sensitivity of the
rDAO is reduced during behavior. However, the inhibition does not appear to be
tailored to specific times during the task or to neurons with specific
receptive field locations on the actively moving limb. The reduction in
sensitivity is as likely to be dependent upon limb posture as on movement. We
conclude that the rDAO discharge provides the cerebellum with information
about vibration or contact during stance; it does not provide reliable
information about undisturbed or disturbed movement. Climbing fiber input from
rDAO might be useful in the preparation to make a movement, but it is probably
not useful for correction of movement errors.
Received 9 February 1996; accepted in final form 7 August 1996.
APS Manuscript Number J104-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996