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1.  Cells in the supraoculomotor area in monkeys with strabismus show activity related to the strabismus angle 
We have earlier shown that monkeys reared with daily alternating monocular occlusion for the first few months of life develop large horizontal strabismus, A/V patterns, dissociated vertical deviation (DVD), and dissociated horizontal deviation (DHD). Here, we present results from neurophysiological experiments that show that neuronal activity of cells within the supraoculomotor area (SOA) of juvenile strabismic monkeys is correlated with the angle of strabismus. There was no modulation of SOA cell activity with conjugate eye position as tested during horizontal smooth pursuit. Comparison of SOA population activity in these strabismic animals and normal monkeys (described in the literature) suggests that both vergence (misalignment in the case of the strabismic animals) thresholds and vergence position sensitivities are different in the strabismic animals compared to the normals. Our data suggest that activity within the SOA cells is important in determining the state of horizontal strabismus possibly by altering vergence tone in extraocular muscle.
PMCID: PMC3285100  PMID: 21950980
strabismus; oculomotor; neurophysiology; near response area; vergence
2.  Signal Processing and Distribution in Cortical-Brainstem Pathways for Smooth Pursuit Eye Movements 
Smooth pursuit (SP) eye movements are used to maintain the image of a moving object relatively stable on the fovea. Even when tracking a single target over a dark background, multiple areas including frontal eye fields (FEF), middle temporal (MT) and medial superior temporal (MST) cortex contribute to converting visual signals into initial commands for SP. Signals in the cortical pursuit system reach the oculomotor cerebellum through brainstem centers including the dorsolateral pontine nucleus (DLPN), nucleus reticularis tegmenti pontis (NRTP) and pretectal nucleus of the optic tract (NOT). The relative information carried in these parallel pathways remains to be fully defined. We used multiple linear-regression modeling to estimate the relative sensitivities of cortical (MST, FEF), pontine (NRTP, DLPN) and NOT neurons to eye- and retinal-error parameters (position, velocity and acceleration) during step-ramp SP of macaques (Macaca mulatta). We found that a large proportion of pursuit-related MST and DLPN neurons were most sensitive to eye-velocity or retinal error velocity. In contrast, a large proportion of FEF and rostral NRTP neurons were most sensitive to eye-acceleration. Visual neurons in MST, DLPN and NOT neurons were most sensitive to retinal image velocity.
PMCID: PMC3057571  PMID: 19645893
cerebral cortex; eye movements; macaque; pontine; pretectum

Results 1-2 (2)