Neural mechanisms for smooth pursuit in strabismus

The visual and oculomotor systems of primates are immature at birth and sensitive to injury. If synergistic interactions between visual and oculomotor systems are compromised during the first months of life, disorders in eye alignment, gaze holding, and smooth pursuit (SP) follow. Here we consider some potential neural mechanisms supporting SP and associated vestibular ocular reflex (VOR) behavior in normal and strabismic monkeys. Experimental strabismus was created by prism goggle wearing or eye muscle surgery in rhesus monkeys (Macaca mulatta). SP and cancellation of the VOR were highly asymmetric in strabismic monkeys during monocular viewing conditions. Similar asymmetric SP and VOR cancellation could be produced in normal monkeys by delivering unilateral muscimol injections to the dorsolateral pontine nucleus (DLPN). We suggest that failure to develop balanced cortical-brainstem circuits in strabismus accounts for many of the components of infantile strabismus syndrome.