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Response characteristics of cerebellar interpositus and intermediate cortex neurons to sinusoidal stimulation of neck and labyrinth receptors

Authors
Journal
Neuroscience
0306-4522
Publisher
Elsevier
Publication Date
Volume
5
Issue
2
Identifiers
DOI: 10.1016/0306-4522(80)90111-6
Keywords
  • Cf
  • Mf

Abstract

Abstract The response characteristics of neurons located in the interpositus nucleus and the intermediate cortex of the cerebellar anterior lobe to sinusoidal rotation of the cervical axis vertebra along the longitudinal axis of the animal, while the head of the animal remained stationary in the horizontal plane, have been examined in precollicular decerebrate cats. A large proportion of interpositus (58.3%) and corticocerebellar units (65.4%) showed a periodic modulation of the firing rate in response to sinusoidal stimulation of neck receptors. The majority of these neurons (78.6%) responded to the angular stimulation in phase with the peak displacement. Most of these positional sensitive units (63.6%) were excited during side-down rotation of the neck and inhibited during side-up rotation, while the remaining units (36.4%) showed the opposite behavior. Within the range of stimulation used the neck afferent system was relatively linear, i.e. the sensitivity of the response, expressed as a percentage change of the average discharge rate per degree of displacement, was only slightly affected by changing the amplitude of neck rotation. Moreover, neither the sensitivity nor the phase angle of the responses were greatly modified by changing frequency of neck rotation. A smaller proportion of interpositus (21.8%) and corticocerebellar units (34.8%) showed a periodic modulation of the discharge rate in response to sinusoidal rotation along the longitudinal axis of the whole animal, leading to stimulation of labyrinth receptors. Two-thirds of these units responded to changes in animal position, due to stimulation of macular receptors. In most of the positional sensitive units (70%), the firing rate decreased during side-down rotation of the animal and increased during side-up rotation, while the remaining units (30%) showed the opposite behavior. These findings indicate that the neck input of one side, elicited during side-down rotation of the neck, exerts a prominent excitatory influence on the ipsilateral intermediate zone of the cerebellum, whereas the macular input of one side, activated during side-down rotation of the animal, exerts a prominent excitatory influence on the contralateral intermediate zone. The macular input was, however, considerably weaker than the neck input. Neurons of the intermediate zone of the cerebellum also received bilateral convergent signals from the fore- and hindlimbs. It is concluded that changes in neck or head position may modify the background discharge of both the fore- and hindlimb regions of the interpositus nucleus and the intermediate cortex, thus affecting the activity of flexor motoneurons during the tonic neck and labyrinth reflexes. In addition, the neck input may modify the response of the intermediate corticonuclear zone of the cerebellum to cutaneous afferent volleys originating from the ipsilateral fore- and hindlimb, for instance during the placing reaction, thus affecting the magnitude of the flexor response underlying this long-loop reflex.

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