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Craig Aaen Stockdale, Robert F. Hess, Timothy Ledgeway; Second-order optic flow processing in amblyopia. Journal of Vision 2007;7(9):393. doi: 10.1167/7.9.393.
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Purpose: Humans with amblyopia show deficits for global motion discrimination that cannot be accounted for by low-level visibility or contrast sensitivity deficits. The processing of translational global motion is deficient in amblyopia [Simmers, A.J., Ledgeway, T., Hess, R.F., & McGraw, P.V. (2003) Vision Res, 43 (6), 729–738] as is the processing of optic flow defined by global motion [Simmers, A.J., Ledgeway, T., Mansouri, B., Hutchinson, C.V., & Hess, R.F. (2006) Vision Res, 46 (16), 2571–2580]. These findings suggest that extra-striate function (i.e., MT and MST) is impaired in amblyopia. Furthermore, deficits in processing of translational motion are more pronounced for second-order stimuli. Here, we asked whether this pattern holds for optic flow stimuli defined by second-order motion and whether deficits are correlated across motion class.
Methods: We used random dot kinematograms in which the dots were areas of increased luminance or contrast of the background noise. Global motion of the dots within the stimulus area was translational, radial or rotational. Coherence thresholds for direction discrimination were obtained across a range of modulation depths.
Results: Our results suggest that motion processing deficits, unrelated to the low-level contrast deficit, occur in our amblyopic group as a whole for translation, rotation, and radial components of optic flow and that these deficits are more pronounced for second-order stimuli. In addition, these first- and second-order deficits are found to correlate.
Conclusions: Extra-striate deficits to global motion and optic flow processing affect the second-order pathway to a greater extent than the first-order. The correlation between first- and second-order deficits is consistent with form-cue invariance in MST.
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