Adaptive changes in the visual cortex after photoreceptor degeneration in retinitis pigmentosa.

Abstract

Retinitis pigmentosa (RP) is a group of hereditary disorders that cause progressive retinal degeneration, affecting the rods and, subsequently, the cones, which results in progressive vision loss. RP is genetically heterogeneous and is inherited in an autosomal dominant, autosomal recessive, X-linked, or sporadic non-Mendelian manner. The recent advancements in repairing damaged retinas highlight the necessity of understanding the impact of photoreceptor degeneration on the visual cortex. This is because functional vision may not be adequately restored if this region is significantly impaired prior to treatment. In the present review, we have analyzed the rodent models of RP that have been most frequently used and the physiological and morphological changes occurring in both humans and rodents with this disorder. Following visually evoked stimulation, the processing of visual information in the primary visual cortex (V1) of individuals with RP is altered due to modifications in the transduction of the signal originating in the degenerated retina. Moreover, alterations in the intrinsic electrophysiological properties of cortical neurons and neural circuits have also been documented. Finally, several neurochemical and/or morphological changes are observed in synaptic structures associated with pyramidal neurons and in select inhibitory interneurons. Nevertheless, despite the physiological and morphological changes that have been described, the impact of RP on the visual cortex does not inevitably result in irreversible damage, as the alterations do not appear to be particularly severe. Brain plasticity is more restricted in adults; however, remodeling of the visual cortex in mice and humans is possible, which encourages further work on therapies capable of partially restoring the lost visual function.