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Chuan Hou, Anthony Norcia, Preeti Verghese, Suzanne McKee; Attention deficits in human strabismic amblyopia measured via neural responses to texture-defined forms: A high-density EEG mapping study. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4984. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
There is evidence that attentional processing in amblyopic observers is abnormal (Kiorpes et al., 2012; Farzin & Norcia, 2011; Popple & Levi, 2008; Sharma et al, 2000). Here we measured high-density Visual Evoked Potential (VEP) responses to texture-defined forms in patients with strabismic amblyopia, and normal vision observers, so that we could compare the magnitude of attention-related neural response modulation in the dominant and amblyopic eyes of patients with those of normal vision participants.
Texture-defined form responses were evaluated in the context of two different behavioral tasks — one where the forms were task-relevant (shape-discrimination of the form) and the other in which they were not (difficult letter task). In both tasks, the participants were presented monocularly with 3 X 3 arrays of 4.5° circular figures that appeared and disappeared from a uniform background at 1 Hz. The figures and background (24° X 24° visual field) were composed of dynamic random bars that were updated at 30 Hz. Because only the task was varied, response differences between the two stimulus configurations reflected the influence of attention.
Directing attention to the shape of the texture-defined form strongly enhanced global responses from the both eyes of normal vision observers and the dominant eye of strabismic amblyopes relative to that measured in the letter task, but only slightly enhanced responses from the amblyopic eye. In addition, the topography of the peak response to the onset of the texture-defined form showed a 15 ms delay in the dominant eyes and a 62 ms delay in the amblyopic eyes of strabismic amblyopes, compared to normal vision participants.
Even though the amblyopic participants were able to execute the two behavorial tasks successfully, the resulting neural modulation due to attention of the texture-defined form response was less in the amblyopic eye. These data provide the first electrophysiological evidence for attentional deficits observed in behavioral studies of amblyopia.
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