[A dual process model for on and off visual evoked potentials].

Abstract

A model of consisting of excitatory and inhibitory processes was proposed for visual evoked potentials (VEPs) from the midline occiput (Oz). On and off stimulation of circular lights subtending 2 degrees and 5 degrees in visual angle were presented with luminance contrast of 1.0, 2.2, and 3.4. The typical triphasic data from a well trained male subject were analysed and decomposed into the two monophasic processes by using the optimal model parameters (amplitude, delay, and peak latency). Then those parameters were predicted by the multiple regression method with the variables for the present experimental conditions. The shapes of the model VEPs were fairly well fitted for ones of the raw data. The model was discussed with its relation to other perceptional phenomena, especially, flickering, forward and backward masking, and spatio-temporal properties, as well as with the physiological aspects. Finally, it was suggested that the dual process model for VEPs would be useful to investigate as well as to explain the spatio-temporal characteristics of the human visual system.