Responses of Purkinje cells of cerebellar vermis to sinusoidal rotation of neck

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Abstract
The response of Purkinje (P) cells located in the vermal cortex of the cerebellar anterior lobe to sinusoidal rotation of the neck was investigated in precollicular decerebrate cats. A selective neck input was elicited by rotating the neck and the body simultaneously along the longitudinal axis of the animal while maintaining the head in horizontal position. Among the 95 P-cells tested for neck stimulation, 35 units showed a mossy fiber (MF) or a climbing fiber (CF) response to sinusoidal rotation of the axis vertebra at the frequency of 0.026 Hz and at the peak amplitude of displacement of 5-10.degree.. The response comprised a periodic modulation of the discharge frequency during sinusoidal rotation of the neck. Most of these units were excited during side-down rotation of the neck, but were inhibited during side-up rotation. The threshold amplitude of neck rotation responsible for the MF-induced responses varied in different units from 1-3.degree. at the frequency of 0.026 Hz. The sensitivity of the units, either did not change or very slightly decreased as a result of increasing amplitude of stimulation from 1-3.degree. to 10-15.degree. at the frequency of 0.026 Hz or by increasing frequency of neck rotation from 0.015 to 0.15 Hz at the amplitude of neck displacement of 5-10.degree.. Changes in amplitude of frequency of stimulation at the parameters reported above did not greatly modify the phase of the unit responses relative to the side-down position of the neck. The MF and CF responses of P-cells to sinusoidal rotation of the neck depended on changes in neck position and not on changes in velocity of neck rotation. The observation that the majority of responding P-cells located in the vermal cortex of the cerebellar anterior lobe increased their firing rate during side-down rotation of the neck is discussed in relation to the results of stimulation and lesion experiments, indicating that postural changes can be elicited either during asymmetric stimulation of neck receptors or by unilateral interruption of the neck afferents.