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Neural Plasticity
Volume 2017 (2017), Article ID 6724631, 10 pages
Research Article

Short-Term Monocular Deprivation Enhances Physiological Pupillary Oscillations

1Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
2CNR Neuroscience Institute, Pisa, Italy

Correspondence should be addressed to Claudia Lunghi

Received 28 October 2016; Accepted 18 December 2016; Published 9 January 2017

Academic Editor: Fang Hou

Copyright © 2017 Paola Binda and Claudia Lunghi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Short-term monocular deprivation alters visual perception in adult humans, increasing the dominance of the deprived eye, for example, as measured with binocular rivalry. This form of plasticity may depend upon the inhibition/excitation balance in the visual cortex. Recent work suggests that cortical excitability is reliably tracked by dilations and constrictions of the pupils of the eyes. Here, we ask whether monocular deprivation produces a systematic change of pupil behavior, as measured at rest, that is independent of the change of visual perception. During periods of minimal sensory stimulation (in the dark) and task requirements (minimizing body and gaze movements), slow pupil oscillations, “hippus,” spontaneously appear. We find that hippus amplitude increases after monocular deprivation, with larger hippus changes in participants showing larger ocular dominance changes (measured by binocular rivalry). This tight correlation suggests that a single latent variable explains both the change of ocular dominance and hippus. We speculate that the neurotransmitter norepinephrine may be implicated in this phenomenon, given its important role in both plasticity and pupil control. On the practical side, our results indicate that measuring the pupil hippus (a simple and short procedure) provides a sensitive index of the change of ocular dominance induced by short-term monocular deprivation, hence a proxy for plasticity.