حالت پایدار بصری پتانسیلهای برانگیخته برای سوسو زدن مانیتور کامپیوتر

In the present study, steady-state visual evoked potentials (S-VEP) in response to amplitude-modulated light from a computer monitor (colour sVGA, 15-inch tube) have been examined. S-VEPs to computer monitors with different refresh rates (60 Hz or 72 Hz) and screen brightness (65 cd/m2 or 6 cd/m2) were recorded in 13 subjects with normal or corrected-to-normal vision. EEG samples were amplified, averaged and stored using Cadwell Excel EMG-EP recorder and a regression model was applied for the amplitude analysis. The mean values of S-VEP amplitude at 60 Hz were found to be significantly higher at 60 Hz refresh rate vs. 72 Hz (F1,12=14.1; P=0.003). Effect of screen brightness (F2,24=6.5; e=0.62; P=0.00075) as well as the interaction effect of refresh rate and screen brightness (F2,24=11.6; P=0.0003) were also found to be significant. Data obtained show that the characteristics of amplitude-modulated light from a computer monitor (frequency, brightness, waveform) are sufficient to elicit S-VEP, and the influence is not only restricted to the peripheral divisions of the visual system as it was shown earlier, but also extends to the central brain structures.

Interrelations between the dynamics of subjective perception of flickering light and brain cortical responses, steady-state visual evoked potentials (S-VEP), have been widely investigated using different kinds of visual stimulation. Van der Tweel and Lunel (1965)found S-VEPs to sinusoidally (100%) modulated light with luminance of approx. 6000 trolands and at temporal frequencies of approx. 60 Hz. Regan (1968)recorded distinctive evoked responses to sinusoidally modulated light at a depth of 33%, with frequencies of 45–60 Hz. Furthermore, S-VEP amplitude increased as stimulus frequency was increased near and beyond the CFF. Some other studies indicated that S-VEPs amplitude declined for frequencies above 50 Hz, but lower brightness and modulation depth were used in those cases (Sokol and Riggs, 1971 and Sternheim and Cavonius, 1972).