Premotor and motor components of reaction time.

Abstract

Reaction time (RT) was fractionated into premotor and motor components based upon the difference between EMG and finger-lift responses. EMGs were recorded from the extensor muscle of the responding forearm during measurement of simple auditory RTs of 54 Ss. The premotor time was that period from the presentation of the stimulus to the appearance of increased muscle firing, while the motor time was that period from this change in action potential to the fingerlift response. 4 preparatory intervals (PI), 0.5, 3.0, 6.0, and 15.0 sec., were used in both a regular and irregular series. Premotor time and RT were highly correlated and showed comparable variations as a function of PI and type of series. Motor time was poorly correlated with RT and was independent of PI and type of series. It was concluded that set, as inferred from the relations between RT and PI and type of series, is a premotoric process.