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Abstract:
Nonlinear properties of the human pupillary light reflex have been studied using binocular light stimuli of sinusoidally varying intensity. As reported earlier, the pupil responds with a net contraction to the modulation of the light intensity within a wide range of modulation frequencies. Results of the present experiments show that the net contraction does not depend upon the relative phase difference of the binocular light stimuli. However in the lower frequency range, where the in-phase stimuli result in a periodic light reflex, the out-of-phase stimuli fail to do so. These results allow certain conclusions to be drawn regarding the localisation within the photopupil reflex arc of the nonlinearities involved.
