Hassankarimi Homa, Jafarzadehpur Ebrahim, Mohammadi Alireza, Noori Seyed Mohammad Reza
Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
Department of Optometry, School of Rehabilitation Science, Iran University of Medical Sciences, Tehran, Iran.
J Ophthalmic Vis Res. 2020 Aug 6;15(3):362-371. doi: 10.18502/jovr.v15i3.7455. eCollection 2020 Jul-Sep.
To evaluate the pattern-reversal visual evoked potential (PRVEP) in low-contrast, spatial frequencies in time, frequency, and time-frequency domains.
PRVEP 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.
As 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.
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.
评估低对比度下，时间、频率和时频域中的空间频率的图形翻转视觉诱发电位（PRVEP）。
根据国际视觉电生理学会（ISCEV）协议，对31只正常眼睛进行PRVEP检查。测试刺激为对比度5%的棋盘格，空间频率分别为1、2和4周/度（cpd）。对于每个VEP波形，使用MATLAB软件进行时域（TD）分析、快速傅里叶变换（FFT）和离散小波变换（DWT）。比较时间、频率和时频维度中VEP成分随空间频率（SF）的变化。
随着SF增加，P100波幅显著衰减，P100潜伏期延长，而频率成分无显著差异。在小波域，对比度为5%时，SF增加会增强DWT系数。然而，这种增加对7P描述符没有显著影响。
在5%的低对比度水平下，与时域和DWT方法相比，傅里叶方法能更好地识别PRVEP参数中与SF相关的变化。然而，小波变换可能会呈现出特定的视觉处理情况。
