Abstract
PurposeTo evaluate the pattern-reversal visual evoked potential (PRVEP) in low-contrast, spatial frequencies in time, frequency, and time-frequency domains.MethodsPRVEP was performed in 31 normal eyes, according to the International Society of Electrophysiology of Vision (ISCEV) protocol. Test stimuli had checkerboard of 5% contrast with spatial frequencies of 1, 2, and 4 cycles per degree (cpd). For each VEP waveform, the time domain (TD) analysis, Fast Fourier Transform(FFT), and discrete wavelet transform (DWT) were performed using MATLAB software. The VEP component changes as a function of spatial frequency (SF) were compared among time, frequency, and time–frequency dimensions.ResultsAs a consequence of increased SF, a significant attenuation of the P100 amplitude and prolongation of P100 latency were seen, while there was no significant difference in frequency components. In the wavelet domain, an increase in SF at a contrast level of 5% enhanced DWT coefficients. However, this increase had no meaningful effect on the 7P descriptor.Conclusion At a low contrast level of 5%, SF-dependent changes in PRVEP parameters can be better identified with the TD and DWT approaches compared to the Fourier approach. However, specific visual processing may be seen with the wavelet transform.
Highlights
We focused on the relationship between spatial frequency (SF) and extracted parameters for the pattern-reversal visual evoked potential (PRVEP) analysis in time, frequency, and time–frequency domains, and compared the efficiency of these dimensions in revealing changes
The 5% contrast was considered as the contrast threshold, given the decrease in Visual evoked potential (VEP) amplitude due to reduction in contrast and the low signal to noise ratio and negligible VEP responses at the contrast levels < 5%.[41]
It has been supposed that differences in the speed of information processing and conduction along the visual pathways, which are preferentially activated by specific spatial frequencies, lead to the sequential visual processing from low to high range of SFs.[11]
Summary
How to cite this article: Hassankarimi H, Jafarzadehpur E, Mohammadi A, Noori SMR. Low-contrast Pattern-reversal Visual Evoked Potential in Different Spatial Frequencies. Low-contrast Pattern-reversal VEP; Hassankarimi et al discrimination and perception may be affected by the contrast level of objects.[3, 4] High-contrast objects and symbols are used in the visual examination room as E or similar acuity charts.[5]
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