Residual cortical responses and network reorganization in inherited retinal degeneration: electrophysiological evidence
Retinitis pigmentosa (RP) progressively deprives the retina of input, but whether the responsiveness of the visual cortex declines in parallel, remains preserved, or increases through compensatory gain remains unclear. Indeed, a weaker visually evoked response cannot, on its own, distinguish these possibilities, since it is equally compatible with a passively degraded input and with an actively…
Retinitis pigmentosa (RP) gradually removes visual input from the retina, but the impact on cortical responsiveness is unclear. Researchers studied whether cortical sensitivity diminishes, stays the same, or increases in response to the retinal degeneration. They compared patients with RP to healthy controls using steady-state visual evoked potentials (SSVEPs) and transcranial magnetic stimulation combined with electroencephalography (TMS-EEG).
SSVEP amplitude followed the expected pattern, being strongest at the center and weakest in the periphery for both groups. However, stimulation of the occipital cortex revealed differences between the groups. Patients with RP showed a larger early negative deflection, stronger beta-band activity, and more efficient connectivity compared to controls.
The impact varied depending on the hemisphere and location of stimulation. These findings suggest that RP does not cause a uniform decline in cortical responsiveness. Instead, the cortex may maintain or even enhance its capacity to respond as retinal input diminishes, indicating a compensatory increase in cortical gain.
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