Visual Stimulation and Electroencephalogram under Scotopic Vision

We tested the visual sensitivity of 15 healthy subjects under scotopic vision using flickering stimulus on the Liquid crystal display (LCD) with a light-emitting diode (LED) backlight (LED-LCD) panel. This test was made to know; 1) if LED-LCD panel might be used for the visual stimulation under scotopic vision, and 2) the minimum trials for ensemble average to get visually evoked potential (VEP). Green, Blue, and Red colors were tested in the darkroom. Electroencephalogram electrodes were used. The brightness of each color was degraded into 255 steps. All participants were asked to watch a circle with red, green, and blue color on the LED-LCD panel. As a result, VEP showed a well-known response pattern when the signals were ensemble averaged for 50 trials. The peak of VEP was not much changed after 25 trials. LED-LCD panel was simple and useful for the simple visual stimulation to test VEP.