Firing behaviour of anticompensatory neurones in the prepositus hypoglossi nucleus of alert cat.

The present results demonstrate that anticompensatory neurones could be recorded within the prepositus hypoglossi nucleus of the alert cat. These neurones, like burster-driving neurones described in paralysed cats, were characterized by a tonic increase of firing for head turning in the contraversive direction (type II) associated to bursts for each vestibular quick phase in the same direction. They were also involved in the generation of visually triggered saccades since they displayed a burst preceding contraversive saccades and a pause in the opposite direction. Thus, these neurones code eye velocity for both vestibular quick phases and visually triggered saccades in addition to head velocity. Such a firing behaviour suggests that, in addition to the classical crossed tecto-reticulo-spinal network, an ipsilateral pathway could also be involved in the generation of visually triggered rapid eye movements.