Adaptation of reflexive fusional vergence is directionally biased

Erkelens, Ian M.; Bobier, William R.

doi:10.1016/j.visres.2018.06.006

Cited by 6 publications

(6 citation statements)

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“…Clinically, the results suggest that fusional and tonic vergence plasticity must be assessed independently. Specifically, a single metric of adaptation may not generalize to the overall function of the disparity-driven vergence system, as we [69] and others have suggested [89]. It is unclear if this would apply to clinical populations, where the dysfunction may be the result of more diffuse, non-cerebellar related impairments.…”

Section: Discussionmentioning

confidence: 79%

“…2-B) Group mean (SE) of the percent change in primary saccade response amplitude and peak velocity from baseline for each block of 10 stimuli during adaptation. changes in stimulus disparity [69] (2 þ 1.5 crossed disparity) after active or sham cTBS (within subject design, n ¼ 13). This double-step paradigm engages both dynamic and tonic vergence adaptation processes [20].…”

Section: Experiments #3: Effect Of Ctbs On the Dynamic Adaptive Elemenmentioning

confidence: 99%

“…Adaptation within the fusional convergence system was achieved using a modified disparity version of the saccadic double-step stimuli, outlined in Experiment #1. Here, the disparity stimuli and experimental design used to induce and evaluate the dynamic adaptation of fusional convergence was identical to our previous work [69]. The same dichoptic apparatus in Experiment #2 was used.…”

Section: Experiments #3 E Objective Assessment Of Tonic and Dynamic Admentioning

confidence: 99%

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A differential role for the posterior cerebellum in the adaptive control of convergence eye movements

et al. 2020

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Introduction: The vergence oculomotor system possesses two robust adaptive mechanisms; a fast "dynamic" and a slow "tonic" system that are both vital for single, clear and comfortable binocular vision. The neural substrates underlying these vergence adaptive mechanisms in humans is unclear. Methods: We investigated the role of the posterior cerebellum in convergence adaptation using inhibitory continuous theta-burst repetitive transcranial magnetic stimulation (cTBS) within a double-blind, sham controlled design while eye movements were recorded at 250hz via infrared oculography. Results: In a preliminary experiment we validated our stimulation protocols by reproducing results from previous work on saccadic adaptation during the classic double-step adaptive shortening paradigm. Following this, across a series of three separate experiments we observed a clear dissociation in the effect of cTBS on convergence adaptation. Dynamic adaptation was substantially reduced while tonic adaptation was unaffected. Baseline dynamic fusional vergence response were also unaffected by stimulation. Conclusions: These results indicate a differential role for the posterior cerebellum in the adaptive control of convergence eye movements and provide initial evidence that repetitive transcranial magnetic stimulation is a viable tool to investigate the neurophysiology of vergence control. The results are discussed in the context of the current models of implicit motor adaptation of vergence and their application to clinical populations and technology design in virtual and augmented head mounted display architectures. Significance statement: The cerebellum plays a critical role in the adaptive control of motor systems. Vergence eye movements shift our gaze in depth allowing us to see in 3D and exhibit two distinct adaptive mechanisms that are engaged under a range of conditions including reading, wearing headmounted displays and using a new spectacle prescription. It is unclear what role the cerebellum plays in these adaptive mechanisms. To answer this, we temporarily disrupted the function of the posterior cerebellum using non-invasive brain stimulation and report impairment of only one adaptive mechanism, providing evidence for neural compartmentalization. The results have implications for vergence control models and applications to comfort and experience studies in head-mounted displays and the rehabilitation of clinical populations exhibiting vergence dysfunctions.

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Section: Discussionmentioning

confidence: 79%

Section: Experiments #3: Effect Of Ctbs On the Dynamic Adaptive Elemenmentioning

confidence: 99%

Section: Experiments #3 E Objective Assessment Of Tonic and Dynamic Admentioning

confidence: 99%

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A differential role for the posterior cerebellum in the adaptive control of convergence eye movements

et al. 2020

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“…A complete description of experimental procedures with schematic illustrations has been described in our previous work 58 and follows other investigations. 41,46 Briefly, participants completed one screening visit to confirm their visual status ( Table), followed by two separate experimental visits.…”

Section: Procedures and Stimulimentioning

confidence: 99%

Reflexive Fusional Vergence and Its Plasticity Are Impaired in Convergence Insufficiency

Erkelens

Bobier

2020

Invest. Ophthalmol. Vis. Sci.

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We compared the adaptive capacities of reflexive fusional convergence and divergence in 10 participants with untreated convergence insufficiency (CI) to 10 agematched binocularly normal controls (BNCs) in an effort to elucidate the functional basis of CI. METHODS. Vergence responses were monitored binocularly at 250 Hz using video-based infrared oculography, while single and double-step disparity stimuli were viewed dichoptically. The double-step stimuli were designed to induce an adaptive increase in the convergence or divergence reflexive fusional response dynamics. RESULTS. As expected, convergence responses in the CI population were significantly slower at baseline (BNC 12.0 ± 1.8°/s vs. CI 7.4 ± 2.5°/s; P < 0.001), but divergence response velocities were similar between groups (P = 0.38). Critically, we observed an impaired adaptive change in convergence peak velocities in the CI group when compared to BNCs (-18.2% ± 27.3% vs. 25.4% ± 9.8%; P < 0.001). Adaptive changes in reflexive fusional divergence responses were similar between groups (P > 0.5) and significantly less robust when compared to BNC convergence. CONCLUSIONS. The results support the hypothesis that the adaptive capacities of vergence are related to the strength of the underlying reflexive fusional response. Combined, the evidence suggests that the clinical condition of convergence insufficiency is underpinned by an underdeveloped or perturbated reflexive fusional vergence response mechanism. We relate these observations to different clinical guidelines for the management and treatment of this condition.

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“…On average, computed vergence distance was about 3 cm shorter than object distance as specified by binocular disparity and familiar size. On the one hand, this is not surprising as other researchers have also found non-perfect vergence distances and considerable individual differences [35, 70–72]. On the other hand, however, we had measured more precise vergence distances in earlier experiments using the same toolbox [48].…”

Section: Discussionmentioning

confidence: 50%

Size matters: How reaching and vergence movements are influenced by the familiar size of stereoscopically presented objects

Schubert¹,

Jung²,

Helmert³

et al. 2019

PLoS ONE

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The knowledge about the usual size of objects—familiar size—is known to be a taken into account for distance perception. The influence of familiar size on action programming is less clear and has not yet been tested with regard to vergence eye movements. In two experiments, we stereoscopically presented everyday objects, such as a credit card or a package of paper tissues, and varied the distance as specified by binocular disparity and the distance as specified by familiar size. Participants had to fixate the shown object and subsequently reach towards it either with open or with closed eyes. When binocular disparity and familiar size were in conflict, reaching movements revealed a combination of the two depth cues with individually different weights. The influence of familiar size was larger when no visual feedback was available during the reaching movement. Vergence movements closely followed binocular disparity and were largely unaffected by familiar size. In sum, the results suggest that in this experimental setting familiar size is taken into account for programming and executing reaching movements while vergence movements are primarily based on binocular disparity.

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Adaptation of reflexive fusional vergence is directionally biased

Cited by 6 publications

References 63 publications

A differential role for the posterior cerebellum in the adaptive control of convergence eye movements

A differential role for the posterior cerebellum in the adaptive control of convergence eye movements

Reflexive Fusional Vergence and Its Plasticity Are Impaired in Convergence Insufficiency

Size matters: How reaching and vergence movements are influenced by the familiar size of stereoscopically presented objects

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