Visual evoked potentials and reaction times: dependence on alpha activity

A reaction task consists of three sequential subtasks, perception, decision, and reaction, which can be modeled by a processing chain. Knowledge of the reaction time, which comprises the processing times of all stages, but normally does not impart knowledge about the single elements of the chain is discussed. An approach to separating processing times of single stages for the visual system by measuring the visual evoked potentials (VEP) is reported. The approach uses ongoing alpha activity and alpha blocking. Correlations between the time course of alpha blocking, the reaction time, and the parameters of the stimuli are shown and compared to the latencies of simultaneously recorded VEPs