Abstract
In the present study the perceptual discrimination threshold (DT) was estimated using a VEP method. At first, to examine the relationship between perceptual judgment and VEPs, 8 subjects of 18 to 22 years old were presented with single and double flashes (the luminosity of a flash was 40 cd/m2). The double-flash interval was varied from DT-20 to DT+20 ms by 10ms steps based on each subject's DT. The VEPs of single-and double-flash were recorded from the occipital area (Oz), and analyzed with “EDAS-software program.” The component of the double-flash VEP to the second stimulus was estimated from the latency of P2 component (about 100ms) or N2 component (about 150ms) of the single flash VEP. It was observed that the latency of P2 component or N2 component of the double-flash VEP to the second stimulus nearly coincided with the P2 or N2 latency of the single flash VEP only when the interstimulus interval (ISI) was longer than the DT. Next, the waves created from summation of the single-flash VEP and the same VEP by DT-20 to DT+20ms delays correlated highly with those of the corresponding actual double-flash VEP. Because of this high degree of similarity in the waveform, double-flash model VEPs were made through summation of the single-flash VEP and the same VEP by 30 to 100ms delays in 10ms steps. It was found that the waves of the double-flash model VEPs to the second flash correlated highly with those of single-flash VEPs only when the ISI used for making the model VEPs was equal to or longer than the DT. These results suggest that the perceptual discrimina-tion threshold of double flashes is estimated by the double-flash VEP models created from the single-flash VEPs.
