Asymmetries between convergence and divergence reveal tonic vergence is dependent upon phasic vergence function

TitleAsymmetries between convergence and divergence reveal tonic vergence is dependent upon phasic vergence function
Publication TypeJournal Article
Year of Publication2017
AuthorsErkelens, I., and W. Bobier
JournalJournal of Vision
Volume17
Pagination1-16
KeywordsAdaptation, adult, Binocular, binocular convergence, binocular vision, Convergence, Direction asymmetry, Disparity vergence, eye movement, Eye Movements, female, human, Humans, male, Ocular, Oculomotor, physiology, Saccades, saccadic eye movement, Vision
Abstract

{Horizontal vergence eye movements are controlled by two processes, phasic and slow-tonic. Slow-tonic responses are hypothesized to be stimulated by the faster, pulse-step neural output of the phasic system. This suggests that the general behavior of each system should be similar; however, this relationship has yet to be investigated directly. We characterize the relationship between phasic and tonic vergence by quantifying directional asymmetries in the response properties of each mechanism to the same disparity amplitudes. Four subjects viewed symmetric steps in disparity dichoptically at 40 cm while eye movements were recorded with infrared oculography. First- and secondorder phasic and slow-tonic convergence response properties increased linearly with disparity demand (p 0.05). Phasic divergence responses were slower than convergence (p = 0.012) and were associated with a higher frequency of saccades (p < 0.001). The average rate of slow-tonic change was correlated to the average peak velocity of phasic vergence at the same vergence demand in both directions

DOI10.1167/17.5.4