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Glen McCormack, Tyler Lowe, Li Deng; Dynamics of registered convergence. Journal of Vision 2007;7(9):72. doi: 10.1167/7.9.72.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: This study tested whether registered convergence - the ability to sense convergence distance - has a temporal tuning function, and if so, whether that function changes when registered convergence interacts with the visual angle motion-in-depth cue.
Methods: Informed consent was obtained from fifteen normally binocular subjects prior to experimentation. Subjects fixated haploscopic luminous targets, in dark surrounds, oscillating in depth at frequencies of 0.06, 0.12, 0.25, and 0.5Hz at a mean distance of 33cm. Three targets manipulated registered vergence and visual angle: “harmonious” (a 25mm maltese cross with congruently changing visual angle and binocular disparity), “conflict” (a 25mm maltese cross of changing disparity but fixed visual angle), and “isolated” (a 0.7mm dot with changing binocular disparity). Perceived motion-in-depth was judged by continuous kinesthetic matching of the unseen hand to target distance. Convergence was measured by infrared oculography. Differences were analyzed by two-way ANOVA with repeated measures.
Results: “Isolated” responses were 47% of the size of “harmonious” responses (p[[lt]]0.001) while “conflict” responses were 37% of the size of “isolated” responses (p[[lt]]0.001). During isolated stimulation there was a 54% reduction of motion-in-depth perception at the 0.06Hz rate compared to the 0.25Hz rate (p[[lt]]0.005). This low frequency loss of response was also evident in conflict stimulation (p[[lt]]0.005), but cue conflict did not appear to alter the temporal tuning function. The rate effect was not significant in harmonious stimulation.
Conclusion: Registered convergence has a low frequency gain reduction which is most evident in isolated cue and cue conflict situations. These findings may help explain some of the differing conclusions drawn previously regarding the role of registered convergence in depth perception. The reduced low frequency response of registered convergence is consistent with the argument that registered convergence may be more useful for directing visually-guided behavior than supporting depth perception.
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