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Abstract:
Comparison of the human pupillary responses to monocular and simultaneous binocular stimuli indicates that the signals evoked in both eyes by binocular stimulation first inhibit each other and then combine by addition. In this paper several possible inhibitory mechanisms are considered and a functional model is proposed which involves a shunting type non-recurrent lateral inhibition. Although the site of inhibitory interaction is not specified by the model, certain assumptions are made regarding the succession of neural events along the pupillomotor pathway. The postulated succession of transmitting stages is: nonlinear transformation, first order lowpass filter with time constant characteristic for the pupillary response, lateral inhibition, addition and second order lowpass filter with the same time constant as before. Besides predicting the experimental data this functional model resolves certain contradictions in the conclusions of different autors regarding the succession of nonlinear transformation and signal combination in the human pupillary system.