[Input pattern from the superior colliculus to vertical eye movement-motoneurons in the cat].

The superior colliculus (SC) plays an important role in the transformation from visual and auditory signals to motor commands to generate saccadic eye movements toward targets. This study investigated the synaptic input patterns into vertical eye movement-related superior and inferior rectus motoneurons from the SC, using intracellular recording and SC stimulating techniques in anesthetized adult cats. I found that the responses obtained from these motoneurons consisted of complex components: a sequence of monosynaptic excitatory postsynaptic potentials (EPSPs), di- or trisynaptic EPSPs or inhibitory postsynaptic potentials (IPSPs) and polysynaptic EPSPs. The amplitudes of the latter two components nearly coincided with the motor map of the SC, which represented the correlation between the sites of SC stimulation and the directions and amplitudes of evoked saccades. I concluded that the SC elicits vertical eye movements through these di- or trisynaptic and polysynaptic pathways in the cat.