Naoto Hara

Ocular convergence-related neuronal responses in the lateral suprasylvian area of alert cats

Neuronal spike discharges were recorded from the lateral suprasylvian (LS) area while ocular convergence was elicited in five alert cats. Ocular convergence was elicited by presenting a visual target moving in depth. Cats were rewarded for convergence eye movement. In 9 out of 426 cells sampled in the caudal postero-medial LS area, the number of spikes was positively correlated with the peak eye velocities during ocular convergence. Significant correlation was found mostly within 400 ms preceding the moment at which the maximum velocity of ocular convergence was obtained. The result favors the hypothesis that the LS area plays an important role in the integrative control of ocular convergence.

Localization of post-traumatic trochlear nerve palsy associated with hemorrhage at the subarachnoid space by magnetic resonance imaging

PURPOSE To report evaluation of traumatic trochlear nerve palsy using head magnetic resonance imaging. DESIGN Observational case reports. METHODS We examined two cases involving trochlear nerve palsy after closed head injury. RESULTS Using a fluid attenuated inversion recovery pulse sequence, MRI showed a high-intensity lesion consistent with subarachnoid hemorrhage at the trochlear nerve area in the ambient cisterns. CONCLUSION An impact force directed toward the tentorium can be a mechanism of injury in some post-traumatic trochlear nerve palsies. Fluid attenuated inversion recovery pulse sequence is a sensitive method for detection of abnormalities in cases associated with head injury.

Effects of localized lesions in the lateral suprasylvian cortex on convergence eye movement in cats

We evaluated the effects of electrolytic lesions in the extrastriate cortical area on the amplitudes and velocities of vergence eye movements in six alert cats that were trained to track a target moving in depth. Bilateral or unilateral lesions in the lateral suprasylvian (LS) cortex reduced the amplitudes and velocities of vergence eye movements, but the positive correlation between them was maintained. Furthermore, unilateral lesions changed the symmetry of eye movements. Movements of the left eye were decreased by lesions in the right LS cortex, resulting in asymmetric vergence eye movement with right eye predominance, and vice versa. These results support the hypothesis that the LS cortex plays an essential role in controlling vergence eye movement.

1541 Effects of extrastriate cortical lesions on ocular convergence

M. TAKAGI’, H. ABE’, R.J. TARMARGO”, D.S. ZEE3 To reveal the role of the dorsal cerebellar vermis in the control of eye movements, we made lesions by surgical aspiration for three rhesus monkeys. Post-lesion, (1) Saccades became hypometric with larger variability. (2) Acceleration and deceleration during saccades were affected to various degrees sometimes producing a lower peak velocity. (3) Saccadic adaptation to a double step paradigm was affected. (4) The later part (40-looms) of initial acceleration of pursuit was decreased. (5) Pursuit adaptation to a double step of velocity paradigm was affected. (6) Eye position became esophoric (around 2 deg.) with abnormal phoria adaptation. However, binocular yoking, disconjugate saccadic adaptation and vergence eye movement were not affected. The dorsal cerebellar vermis participates in the on-line control and long-term adaptation of a variety of aspects of saccades and pursuit but primarily those related to conjugate (cyclopean) eye movement control.