Non-synaptic Mechanism of Ocular Dominance Plasticity
Classic experiments showing that monocular visual disruption alters synaptic connections to binocular neurons in the brain established the fundamental concept of synaptic plasticity through coincident spike time arrival. However, if the speed of impulse transmission from the eye is altered by visual deprivation, spike time arrival at binocular neurons would be affected, thereby inducing synaptic plasticity. This possibility is tested here in adult mice by monocular eyelid suture and action potential inhibition in retinal axons. The results show that spike time arrival in visual cortex is altered by monocular visual disruption in association with morphological changes in myelin (nodes of Ranvier) on axons in optic nerve and optic tract. This non-synaptic mechanism of ocular dominance plasticity, mediated by myelin-forming cells, supplements and may drive synaptic plasticity.