Identify mechanisms of amblyopia in Gabor orientation identification with external noise.

In this study, we applied the external noise method and the PTM model to identify mechanisms underlying performance deficits in amblyopia. Amblyopic and normal observers performed a Gabor orientation identification task in fovea. White external noise was added to the Gabor stimuli. Threshold versus external noise contrast (TvC) functions were measured at two performance criterion levels. For a subset of observers, we also manipulated the center spatial frequency of the Gabor. We found that two independent factors contributed to amblyopic deficits: (1) increased additive internal noise, and (2) deficient perceptual templates. Whereas increased additive noise underlay performance deficits in all spatial frequencies, the degree of perceptual template deterioration increased with the center spatial frequency of the Gabor.