Abstract
Several previous studies have reported smooth pursuit to non-visual stimuli. We reexamined these claims using visual, auditory, proprioceptive, and touch stimuli. Subjects' eye movements were recorded using scleral search coils as they watched, heard, felt or moved a pendulum. Visual stimuli were pursued with high gain values and few small amplitude catch-up saccades. Auditory stimuli produced very low gains and rare instances of smooth pursuit. The proprioceptive condition, in which the subject held the pendulum and tracked its motion in the dark, produced short periods of smooth pursuit in some people. A tactile condition, in which the pendulum rolled along the subjects' arm, also produced limited segments of smooth pursuit. These two conditions were frequently interrupted by a significantly greater number of larger amplitude catch up saccades and reflected significantly lower gain values. These results force us to conclude that even under optimal circumstances it is not possible for proprioceptive or somatosensory stimuli to produce extended periods of smooth pursuit although isolated instances of smooth pursuit are observed. Not surprisingly, visual stimuli are unequivocally the best producers of smooth pursuit while auditory stimuli rarely elicit smooth pursuit.