Abstract
Purpose :
Retinitis Pigmentosa (RP) is a visual disorder affecting tens of thousands of individuals every year. During the progression of RP, rod then cone photoreceptors are lost. As photoreceptors are lost, individuals with RP suffer a variety of visual impairments including night blindness, tunnel vision, loss of visual acuity, loss of depth perception, and in some cases total blindness. The most common cause of autosomal dominant RP is from P23H rhodopsin mutation. Longitudinal studies of patients with RP reveal that loss of visual acuity significantly lags loss of photoreceptors. A current gap in knowledge is how loss of visual acuity correlates with neuronal tuning properties in primary visual cortex. Our hypothesis is that as visual acuity is diminished, neuronal responses in V1 will be reduced at higher spatial frequencies.
Methods :
Animals with rho P23H/+ mutation display adult onset retinopathy characteristic of RP. Animals with the rho P23H/+ mutation and wild-type controls are tested on the visual water task (VWT), a validated behavioral assay to measure visual acuity. Animals are tested for acuity at both light-adapted and dark-adapted conditions. Then utilizing 2-photon calcium imaging in both mice with the rho P23H/+ mutant mice and wild-type controls, we examine differences in functional properties of discrete neurons in layer ii/iii of visual cortex under both light-adapted and dark-adapted conditions. We image neurons in awake, head-fixed mice freely running on a styrofoam ball while presenting a battery of gratings at varying spatial frequency and orientation to measure tuning properties of hundreds of neurons per mouse.
Results :
Neurons in V1 of rho P23H/+ mice have a significant reduction response to higher spatial frequencies at both light-adapted and dark-adapted conditions when compared to age-matched controls.
Conclusions :
Populations of neurons in V1 of mice with autosomal dominant rho P23H display a reduction of neuronal responses to high spatial frequencies at both light-adapted and dark-adapted conditions. Whether this reduction in response properties precede or accompany loss of visual acuity is unknown.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.