EFFECTS OF AMBLYOPIA ON INTRINSIC ELECTROPHYSIOLOGY OF BINOCULARLY INNERVATED NEURONS IN THE MOUSE SUPERIOR COLLICULUS

In amblyopia, an imbalance of acuity between the eyes leads to altered binocular vision. Years of work have demonstrated the impact of amblyopia on the primary visual cortex, but persistent deficits in visuomotor control suggest subcortical areas may also be affected. Recent work suggests that the superior colliculus (SC) is negatively impacted in human amblyopes, and monocular deprivation (MD) studies in mice suggest that SC neurons exhibit ocular dominance plasticity. However, the mechanisms underlying this plasticity and the extent to which different SC neuron populations express it remains unclear. To interrogate these open areas, we assessed the impact of MD on the intrinsic properties of SC neurons directly innervated by both eyes. We labeled binocularly innervated SC neurons using an intersectional, trans-synaptic tracing strategy and used fluorescent microscopy to target them for current clamp recordings. Ongoing experiments indicate that binocular neurons in the ipsilateral SC to the deprived eye exhibit faster action potentials and higher frequency in response to current injections when compared to binocular neurons in the contralateral SC or in sham conditions. In contrast, contralateral neurons display lower firing frequency than both ipsilateral and sham neurons. This suggests that amblyopia leads to hemisphere-dependent synaptic rewiring in the SC. Monocular deprivation caused reduced excitability and firing capacity of contralateral neurons, while increasing excitability and firing frequency in ipsilateral cells. Current work is focused in determining the changes in synaptic activity in binocular neurons in both hemispheres.