Slow eye movements serve to stabilize the retinal image. Despite their importance, the neurons controlling slow movements have received relatively little attention. These important areas for slow eye movements will be studied: paramedian pontine reticular formation (PPRF), prepositus hypoglossi nucleus (PH) and vestibular nuclei (VN). A large sample of such PPRF, PH and VN neurons will be recorded so that the distribution of properties can be described. Firing patterns during the vestibulo-ocular reflex (VOR), the optokinetic reflex (OKR), pursuit and saccades will be recorded and related to eye movements, head rotation, and visual stimuli via computer. Data will be compared with a computer model describing the eye, orbit, muscles, motoneurons, signal summation points and the neuronal integrator (which converts head velocity to eye position). The connectivity of PPRF eye-position neurons is unknown because they can only be identified physiologically. To clarify this, one microelectrode will be placed into the 6th nucleus; a second microelectrode will record from a single PPRF eye-position neuron. This unit's spikes will trigger a computer of average transients to average the 6th-nucleus field position. A monosynaptic excitatory connection to abducens neurons will be revealed by a wave of negativity about 1 msec after the spikes. These studies will elucidate cognitive mechanisms by which monkeys and men investigate their visual surrounds and will help elucidate the pathophysiology of eye-movement deficits and nystagmus of central origin.
