Dichoptic Perceptual Training and Sensory Eye Dominance Plasticity in Normal Vision

Abstract

Purpose We introduce a set of dichoptic training tasks that differ in terms of (1) the presence of external noise and (2) the visual feature implicated (motion, orientation), examining the generality of training effects between the different training and test cues and their capacity for driving changes in sensory eye dominance and stereoscopic depth perception. Methods We randomly assigned 116 normal-sighted observers to five groups (four training groups and one no training group). All groups completed both pre- and posttests, during which they were tested on dichoptic motion and orientation tasks under noisy and noise-free conditions, as well as a binocular phase combination task and two depth tasks to index sensory eye dominance and binocular function. Training groups received visual training on one of the four dichoptic tasks over 3 consecutive days. Results Training under noise-free conditions supported generalization of learning to noise-free tasks involving an untrained feature. By contrast, there was a symmetric learning transfer between the signal-noise and no-noise tasks within the same visual feature. Further, training on all tasks reduced sensory eye dominance but did not improve depth perception. Conclusions Training-driven changes in sensory eye balance do not depend on the stimulus feature or whether the training entails the presence of external noise. We conjecture that dichoptic visual training acts to balance interocular suppression before or at the site of binocular combination.

Neural Correlates of Sensory Eye Dominance in Human Visual White Matter Tracts

“…In only a little over half of our participants (53.7%) was there eye dominance agreement across both SED indexing tasks. This observation, however, is not surprising in light of previous work demonstrating comparably weak consistency across standard SED tasks when indexing eye dominance in the neurotypical population (García-Pérez & Peli, 2019;Kam & Chang, 2021). If we look only at the subset of our participants with strong eye dominance (2 s.d.…”

“…The mechanistic origins of SED remain difficult to unravel as it has been indexed using behavioral measures involving a variety of visual features and task types. SED is commonly indexed by binocular phase combination ( Ding and Sperling, 2006 ; Zhou et al, 2013 ), binocular rivalry ( Levelt, 1965 ; Blake, 1989 ), and more recently, dichoptic signal-in-noise (SNR) tasks ( Li et al, 2010 ; Kam and Chang, 2021 ). Binocular phase combination tasks present slightly different gratings to each eye and typically allow the observer to adjust the phase, or contrast of the inputs, thereby revealing the relative contribution of each eye’s input to the fused percept (i.e., by indexing a contrast ratio and/or relative phase shift between the two eyes).…”

“…Dichoptic signal-in-noise tasks require observers to suppress noise information presented to one eye and extract useful information (signal) presented to the other eye. The dichoptic motion SNR task appears to be a sensitive metric for measuring changes in SED after perceptual training ( Kam and Chang, 2021 ). Although these tasks purportedly all reflect SED, it is unclear as to whether they reflect the same mechanisms.…”

Sensory Eye Dominance Plasticity in the Human Adult Visual Cortex

“…To probe the potential loci of eye balance plasticity, we previously introduced four dichoptic training tasks that differed in terms of the presence of external noise and the visual feature implicated and examined their capacity to drive changes in sensory eye dominance (Kam and Chang, 2021). We found that changes in sensory eye dominance do not depend on the trained task or visual feature, suggesting that the dichoptic training paradigm may at least partially act to balance interocular suppression before or at the site of binocular combination.…”

“…In particular, a visual training protocol using dichoptically presented signal-in-noise motion stimuli has gained special traction as it has been demonstrated to effectively reduce eye dominance in both the visually impaired (Hess et al, 2010) and normal observers (Kam and Chang, 2021). To date, much of the research has been focused on developing different paradigms to promote eye-rebalancing (Li et al, 2013;To et al, 2011;Tuna et al, 2020;Xu et al, 2012Xu et al, , 2010, but very little work has been done to reveal the neural underpinnings of sensory eye dominance and its plasticity.…”