Normalization of visual evoked potentials using underlying electroencephalogram levels improves amplitude reproducibility in rats.
OBJECTIVE
The visual evoked potential (VEP) is a frequently used noninvasive measurement of visual function. However, high-amplitude variability has limited its potential for evaluating axonal damage in both laboratory and clinical research. This study was conducted to improve the reliability of VEP amplitude measurement in rats by using electroencephalogram (EEG)-based signal correction.


METHODS
VEPs of Sprague-Dawley rats were recorded on three separate days within 2 weeks. The original VEP traces were normalized by EEG power spectrum, which was evaluated by Fourier transform. A comparison of intersession reproducibility and intersubject variability was made between the original and corrected signals.


RESULTS
Corrected VEPs showed lower amplitude intersession within-subject SD (Sw), coefficient of variation (CoV), and repeatability (R(95)) than the original signals (P < 0.001). The intraclass correlation coefficient (ICC) of the corrected traces (0.90) was also better than the original potentials (0.82). For intersubject variability, the EEG-based normalization improved the CoV from 44.64% to 30.26%. A linear correlation was observed between the EEG level and the VEP amplitude (r = 0.71, P < 0.0001).


CONCLUSIONS
Underlying EEG signals should be considered in measuring the VEP amplitude. In this study, a useful technique was developed for VEP data processing that could also be used for other cortical evoked potential recordings and for clinical VEP interpretation in humans.
Department of Ophthalmology, Australian School of Advanced Medicine, Macquarie University, Sydney, New South Wales, Australia. yuyi.you@gmail.com
Yuyi
Y
You
Johnson
J
Thie
Alexander
A
Klistorner
Vivek K
VK
Gupta
Stuart L
SL
Graham
D000818:Animals; D004569:Electroencephalography / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D014786:Vision Disorders / Q000175:diagnosis / Q000503:physiopathology