Training in contrast detection improves motion perception in amblyopia

Abstract

Many recent studies have suggested that perceptual learning could be a potential treatment for adults with amblyopia. One critical concern is whether training with one particular stimulus and task generalizes to other stimuli and tasks. Huang, Zhou, & Lu (2008) examined the issue in the spatial domain and found that the improvement at the training frequency could generalize to other spatial frequencies; and the bandwidth of the improvement was much broader in amblyopic vision than in normal vision. Here, we evaluated the bandwidth of perceptual learning in amblyopic vision in the temporal domain. Previous studies on motion deficits in amblyopia (Qiu et al., 2006) suggested that they are caused by spatial vision deficits. We hypothesized that training in the spatial domain could benefit motion perception. Seven anisometropic and two strabismic adult amblyopes (age: 22.1 ± 5.64) were trained in a contrast detection task using a 3 × 3 deg, 118 ms Gabors at their individual cutoff spatial frequency in their amblyopic eye for 10 days. Spatial contrast sensitivity functions and temporal modulation transfer functions for both motion detection and discrimination were measured for both eyes before and after training. In the amblyopic eye, training in Gabor detection near cutoff spatial frequency improved (1) contrast sensitivity by 6.6 dB across spatial frequencies, with a bandwidth of 4.4 (SE = 0.05) octaves, (2) sensitivity of motion detection and discrimination by 3.2 and 3.7 dB across temporal frequencies, respectively, with bandwidths of improvement of 3.9 (SE = 0.1) and 3.1 (SE = 0.05) octaves, and (3) visual acuity by 3.2 dB. The fellow eye also showed small amount of improvements. Control subjects who received no training showed no obvious improvement in any measurements. These results demonstrate substantial plasticity in the amblyopic visual system, and provide new empirical support for perceptual learning as a potential treatment for amblyopia.