Influence of foveal afterimage on non-visually induced pursuit eye movements.

Smooth pursuit eye movements (SPEMs) were measured during trials with an acoustic target, a somatosensory target (finger tip), and an imaginary target. Under these non-visual conditions the induced SPEMs were investigated both with and without a foveal afterimage. Ten normal subjects were examined. Considerable inter-individual differences were observed in performance of the non-visual SPEMs. However, the presence of an afterimage did not influence SPEMs during acoustic or somatosensory pursuit. It is concluded that the capacity for visualization may not involve the ability for non-visual SPEMs. As in imaginary target condition the subjects could not elicit SPEM without the afterimage, clearly the memory of target motion alone cannot generate SPEMs. The afterimage may help the subject to convert the memory of target motion into the perception of virtual target motion.