Effects of electrical stimulation of low-threshold muscle afferents on visual reaction time

Human subjects performed plantar flexions of the foot in visual reaction time (RT) situations. In the simple RT task, the same foot had to be moved during the whole session, in the choice RT task, the right or left foot was moved in a random sequence. Low-threshold muscle afferents which evoked a monosynaptic H reflex were electrically activated on both sides at various intervals after the onset of the light stimulus. In both RT situations. RT was shortened equally by the electrical stimulation. The intersensory facilitation in the choice RT task provided support for the preparation enhancement model, since the subjects could not react to the electrical stimulus alone.