AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 3 813-R819, Copyright © 1990 by American Physiological Society
Light and target distance interact to control pupil size
G. A. Myers, S. Barez, W. C. Krenz and L. Stark
Department of Engineering Science, University of California, Berkeley 94720.
Light and target distance stimuli were presented to normal human subjects,
and their pupillary responses were measured. A homeomorphic computer model
of the pupillary control system is presented in which the form of
interaction of controller signals due to light and target distance was
investigated. The error remaining when model parameters were optimized to
fit experimental pupil size (area or diameter) was smaller for the linear
interaction hypothesis than for either power law or logical law
interaction. A generalized second-order nonlinear model with six parameters
(vs. 3 for each of the other models) yielded somewhat lower residual error.
With the use of a modified Akaike information criterion, the value (in an
information theoretic sense) of the improved fit afforded by the three
additional parameters in the generalized nonlinear model was shown to be
small, and thus the generalized second-order nonlinear model was rejected
in favor of the simpler and more parsimonious linear model.
