Broad bandwidth of perceptual learning in the visual system of adults with anisometropic amblyopia

Abstract

Recent studies have demonstrated that training adult amblyopes in simple visual tasks leads to significant improvements of their spatial vision. One critical question is: How much can training with one particular stimulus and task generalize to other stimuli and tasks? In this study, we estimated the bandwidth of perceptual learning in teenage and adult observers with anisometropic amblyopia and compared it to that of normal observers. We measured and compared contrast sensitivity functions-i.e., sensitivity to sine-wave gratings of various spatial frequencies-before and after training at a single spatial frequency in teenagers and adults with and without amblyopia. We found that the bandwidth of perceptual learning in the amblyopic visual system is much broader than that of the normal visual system. The broader bandwidth, suggesting more plasticity and wider generalization in the amblyopic visual system, provides a strong empirical and theoretical basis for perceptual learning as a potential treatment for amblyopia.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Schematic diagram of the bandwidth of perceptual learning. The bandwidth of perceptual learning can be estimated by subtracting the pretraining contrast sensitivity function from the post-training contrast sensitivity function.

Fig. 2.

Learning curves—contrast sensitivity as a function of training sessions—for the amblyopic group and two control groups. Average data from pre- and post-training CSF measurements (the first and last data points) and eight training sessions are shown. The black symbols and lines represent the average of all of the observers in each group. The gray symbols and lines represent the average of the observers who exhibited significant learning during training.

Fig. 3.

Pre- and post-training contrast sensitivity functions (black symbols and curves; left ordinate) and the difference between the best fitting post- and pretraining CSFs (dashed gray curves; right ordinate) in the amblyopic eyes of the amblyopic group, subjects S1–S10. Triangles, pretraining; circles, post-training; arrows, training frequency; error bars, SEM.

Fig. 4.

Pre- and post-training contrast sensitivity functions (black symbols and curves; left ordinate) and the difference between the best fitting post- and pretraining CSFs (dashed gray curves; right ordinate) in the trained eyes of the first control group, subject S11–S24. Triangles, pretraining; circles, post-training; arrows, training frequency; error bars, SEM.

Fig. 5.

Average contrast sensitivity improvements as a function of spatial frequency for the amblyopic group (Left) and first control group (Right). The magnitudes of contrast sensitivity improvements were normalized to that at the training spatial frequency; spatial frequencies were normalized to the training frequency. Arrows indicate the average training spatial frequency. Data were weighted by their standard deviation. Only observers with significant contrast sensitivity improvements during training are included. Error bars indicate SEM.