[Electrophysiological experiment on neuronal pathway controlling horizontal eye-head coordination in the cat]

Tectal di-synaptic postsynaptic potentials (EPSPs) recorded in the abducens internuclear neurons (6 IN) were invariably facilitated by conditioning peduncular stimulation in the cat, which indicated that tectal and cortical excitation of 6 IN were mediated by a common set of interneurons. Using an extracellular recording technique, those common interneurons were identified as reticulospinal neurons by showing axonal projection to C2-3 spinal segment; they were also found to distribute mainly to the medial region of the nucleus reticularis pontis caudalis immediately rostral to the abducens nucleus, and not in the medullary reticular formation caudal to the abducens nucleus. The present experiment suggested that integration of tectal and cortical commands for horizontal eye-head coordination are taking place in the reticular formation rostral to the abducens nucleus which has been called the paramedian pontine reticular formation in the cat.