EEG recordings during binocular rivalry reveals changes of binocular interaction following perceptual learning in adult amblyopia

Abstract

Purpose : Perceptual learning (PL) can significantly improve spatial vision in adult amblyopia. How PL changes neural processing of visual information processing in amblyopia is however not clear. In this study, we used steady state VEP (SSVEP) to reveal changes of binocular processing following perceptual learning in anisometropic amblyopia.

Methods : Seventeen adults with anisometropic amblyopia (mean age = 16.54± 5.03years) participated in monocular training in a contrast detection task with their amblyopic eye. Before and after training, the contrast sensitivity function (CSF) was measured using the quick CSF method. In addition, SSVEP was recorded while subjects viewed binocular rivalry stimuli made of a pair of incompatible circular checkerboard patterns that reversed their contrast at f1 =6 Hz and f2=7.5 Hz. The Z-value (a measure of signal to noise ratio) of the intermodulation (IM) component f1 + f2 was used as a frequency-tagged signal associated with binocular interaction.

Results : We divided the subjects into two groups based on the interocular AULCSF (the area under the log CSF) difference before training (high group, n=8, difference > 0.6 log units; low group, n=9, difference < 0.6 log units). We found that the high group had significantly lower IM scores [mean = 1.14, CI = (.08, 2.21)] than the low group [mean = 3.35, CI = (1.82, 4.88)] (t = -2.72, P = 0.016). The results suggested that IM scores may reflect interocular difference in contrast sensitivity. Following perceptual learning, the FE VA improvement is 0.01±0.15 lines (t=0.418, P=0.681), yet the AE VA significantly improves by 1.10±1.62 lines (t=2.97, P=0.013). Wilcoxon signed-rank test shows that interocular AULCSF difference is not significant(Z=-1.586, P=0.113). However, the change of AULCSF difference was correlated with the change of IM scores (r = -0.773, P< 0.001). The correlation remained significant (β = - 0.78, P= 0.002) after controlling the influence of EEG components associated with monocular processing (f₁, f₂, 2f₁, and 2f₂).

Conclusions : Perceptual learning in the amblyopic eye significantly reduced interocular difference of the contrast sensitivity in adult amblyopia. The behavioral changes are correlated with SSVEP measures of interocular interaction. We conclude that monocular training in the amblyopic eye could improve binocular processing in amblyopia.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.