title: Perceptual learning improves adult amblyopic vision through rule-based cognitive compensation.
abstract: OBJECTIVE
  We investigated whether perceptual learning in adults with amblyopia could be enabled to transfer completely to an orthogonal orientation, which would suggest that amblyopic perceptual learning results mainly from high-level cognitive compensation, rather than plasticity in the amblyopic early visual brain.
  
  
  METHODS
  Nineteen adults (mean age = 22.5 years) with anisometropic and/or strabismic amblyopia were trained following a training-plus-exposure (TPE) protocol. The amblyopic eyes practiced contrast, orientation, or Vernier discrimination at one orientation for six to eight sessions. Then the amblyopic or nonamblyopic eyes were exposed to an orthogonal orientation via practicing an irrelevant task. Training was first performed at a lower spatial frequency (SF), then at a higher SF near the cutoff frequency of the amblyopic eye.
  
  
  RESULTS
  Perceptual learning was initially orientation specific. However, after exposure to the orthogonal orientation, learning transferred to an orthogonal orientation completely. Reversing the exposure and training order failed to produce transfer. Initial lower SF training led to broad improvement of contrast sensitivity, and later higher SF training led to more specific improvement at high SFs. Training improved visual acuity by 1.5 to 1.6 lines (P < 0.001) in the amblyopic eyes with computerized tests and a clinical E acuity chart. It also improved stereoacuity by 53% (P < 0.001).
  
  
  CONCLUSIONS
  The complete transfer of learning suggests that perceptual learning in amblyopia may reflect high-level learning of rules for performing a visual discrimination task. These rules are applicable to new orientations to enable learning transfer. Therefore, perceptual learning may improve amblyopic vision mainly through rule-based cognitive compensation.
authors.affiliation: Department of Psychology, IDG/McGovern Institute for Brain Research, and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China.
authors.forename: Jun-Yun
authors.initials: JY
authors.lastname: Zhang
authors.forename: Lin-Juan
authors.initials: LJ
authors.lastname: Cong
authors.forename: Stanley A
authors.initials: SA
authors.lastname: Klein
authors.forename: Dennis M
authors.initials: DM
authors.lastname: Levi
authors.forename: Cong
authors.initials: C
authors.lastname: Yu
mesh_terms: D000328:Adult; D000550:Amblyopia / Q000503:physiopathology* / Q000523:psychology; D003071:Cognition / Q000502:physiology*; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D009949:Orientation / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics / Q000379:methods; D014792:Visual Acuity; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: amblyopia; orientation; perceptual learning