Purchase this article with an account.
Yossi Mandel, Adi Gross, Nairouz Farah; Characterization of Focal Electroretinogram and Visual Evoked Potential in Normal Pigmented Rats. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5342.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Measurements of focal retinal function are highly important in assessing intervention efficiency in various research models where a localized area of the retina is treated (e.g. retinal prostheses, genetic therapy). This work characterized the focal Electroretinogram (fERG) and Visual Evoked Potential (fVEP) in response to a photopic localized visual stimulus projected on the rat retina.
fERGs and fVEPs signals were recorded in Long-Evans anesthetized rats in response to LED flashes relayed through circular apertures which are incorporated into a fundus camera (Micron IV, Phoenix Research Lab) optical path. Stimuli with varying irradiances, repetition rates, and spot diameters were investigated at various background illumination. VEP signals were recorded using intracranially implanted screws over the primary visual cortex (V1) and ERG signals were recorded using a corneal contact electrode. Raw data were analyzed by a customized software.
The fERG bwave amplitude increased with light intensity reaching a plateau at 4*103 cds/m2, and decreased with increasing stimuli repetition rate and increasing background illumination. The fVEP amplitude (N1P2) demonstrated a similar trend, however, a plateau was observed at a lower stimuli luminance (1*103cds/m2) suggesting a smaller cortical dynamic range as compared to the retina. fERG and fVEP b-wave amplitude increased with stimuli spot size reaching a plateau at smaller spot size for high intensity illumination levels, suggesting a contribution of the scatter effect. The b-wave latency decreased with increasing stimuli luminance, reaching a minimum at luminance levels above 10cds/m2. The photopic stimuli elicited a robust photopic negative response (PhNR) with increasing amplitude and latency for increasing stimuli irradiance and spot size.
We present a thorough characterization of the effect of various stimuli parameters on fERG and fVEP signals in normal pigmented rats. The obtained signals reveal a robust PhNR component and suggest a scatter effect at high irradiance stimuli. Furthermore, our results demonstrate the larger retinal dynamic range as compared to the cortical dynamic range under photopic conditions. This study can serve as a basis for evaluating localized retinal function as an important research tool for investigating retinal diseases in rodents.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only