Participation of medial pontine reticular formation in eye movement generation in monkey.

THE DEEP CORE Of the brain particular the med ial pontine stem, reticu and in lar formation (PRF), has long been considered to be directlv involved in the immediate supranuclear control of eye movements. This belief is based on the demonstration of direct anatomic connections from this area to all the oculomotor nuclei (ZZ), on the severe and permanent disruption of eye movement that results from focal lesions placed in this area (3), and on the shortlatency eye movements that are evoked by electrical stimulation in this area (6). Single-neuron recordings in this or closely adjacent brain stem areas (5, 7, 8, 15, 24) have revealed several categories of neural activity that is closely and differentially correlated with various types of eye movemen ts. These previous studies have either been conducted on animals without the primate’s repertory of eye movements (7, S), have been brief, qualitative reports concerned only with segregating the units by type (5, 24), or have not considered unit behavior during smooth pursuit or vestibularly driven movements (15). It has been previously shown that each oculomotor neuron participates in all the types of primate eye movement (21). Therefore, in working out the details of the supranuclear organization of the oculomotor system the question that remains to be clarified is how and at what level signals from the various separate eye-movement-generating subsystems are brought together. In this respect it is important to have .more precise and detailed recordings on each type of reticular formation whose activity is correlated with