Visual 'cortical-recipient' and 'tectal-recipient' pontine zones play distinct roles in cat visuomotor performance

In order to test the hypothesis that visual information reaching the cerebellum through the pontine nuclei is involved in the control of visually guided movements, the effects of bilateral kainic acid pontine lesions have been analysed in cats performing a reaching movement towards a spot of light that was either stationary or moving. In 4 cats, the lesion was restricted either to the ventromedian region (cortical-recipient zone) or to the dorsolateral nucleus (tectal-recipient zone) of the pons. A major and persistent impairment was seen when the cerebellum was deprived of the pontine information influenced by the colliculus. While cats displayed no impairment when reaching towards a stationary target, they exhibited a strong accuracy deficit associated with an increased reaction time when reaching towards a moving target. In contrast, lesioning the pontine zone influenced by the visual cortex induced a transient accuracy deficit with moving targets and a transient delay in movement onset whatever the mode of target presentation. These results emphasise the involvement of visual pontine regions in the guidance of movements; they also confirm previous results showing that tectal visual information plays a more important role than that originating in the visual cortex when movements are directed towards moving targets.