Neck and macular labyrinthine influences on the purkinje cells of the cerebellar vermis

1. The present experiments have shown that P-cells located in the vermal cortex of the cerebellar anterior lobe, particularly in the longitudinal parasagittal zone which projects to the ipsilateral LVN, can monitor both the signals which originate from the macular receptors, as well as those which originate from the cervical receptors as a result of the displacement of the neck. MF- and/or CF-responses of the same or of different P-cells to the two inputs were observed. 2. The sensitivity of the MF-response of the P-cells to the neck input elicited by sinusoidal rotation of the neck was higher than that of the MF-response of the P-cells to the macular input elicited by sinusoidal tilt along the longitudinal axis of the whole animal. 3. Most of the MF-response of the P-cells to the neck input were characterized by an excitation during side-down rotation of the neck and by an inhibition during side-up rotation, whereas most of the MF-response of the P-cells to the macular input showed just the opposite behaviour. 4. Units which received a convergence from both neck and macular receptors and showed an antagonistic pattern of response to the two inputs were tested during rotation of the head alone, in order to simultaneously excite the two kinds of receptors. Due to the higher sensitivity of the neck over the macular response, the magnitude of the combined response tended to be similar to the difference between the individual ones. Moreover, the phase of the resulting response became in some instances more related to the velocity of neck rotation than to the neck position. 5. These findings indicate that the conflict between the neck input and the macular input is only partially resolved at wrticocerebellar level and that the suppression of the conflicting response may occur either at medullary (LVN) or at spinal cord level.