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Elizabeth Saionz, Duje Tadin, Krystel Huxlin; Relative efficacy of global motion versus contrast training early after stroke for recovering contrast sensitivity in cortical blindness. Journal of Vision 2018;18(10):267. doi: https://doi.org/10.1167/18.10.267.
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© ARVO (1962-2015); The Authors (2016-present)
Stroke damage to V1 in adult humans causes cortical blindness (CB). Visual discrimination training in chronic (>6 months) CB patients improves their deficit, although recovered vision - particularly contrast sensitivity (CS) - remains impaired. Consistent with evidence from sensorimotor stroke that earlier intervention promotes greater recovery, global direction discrimination (GDD) training initiated subacutely (< 3 months) after stroke generates faster, more spatially distributed discrimination improvements compared to identical training in chronic CB. Here, we investigated the effect of training in 9 CBs < 3 months post-stroke. In seven CBs, initial blind field GDD performance was at chance, so they trained on GDD. Surprisingly, 2 CBs had normal GDD performance in their blind fields, so they trained on static orientation discrimination in which contrast was varied to increase difficulty. After daily home training for 3 months, we assessed changes in static (vertical-horizontal orientation discrimination) and motion (left-right direction discrimination) CS using the quick CS function (qCSF) method. In the GDD-training group, initial blind field qCSFs were flat (static and motion). In the contrast-training group, initial blind field static qCSFs were flat but motion qCSFs were not. Following training, the GDD-trained group showed no improvement in static qCSFs but mildly improved sensitivity on motion qCSFs between 0.2-1 cycles/degree (cpd). The contrast-trained group showed no further improvement in motion qCSFs but robust improvement in static qCSFs between 0.2-1.5 cpd. Consistent with this, contrast-trained subjects improved more on clinical visual fields (Humphrey perimetry) compared to GDD-trained CBs, with greater perimetric mean deviation gains (contrast trained: +2.98 dB; GDD trained: +0.716 dB, p=0.024) and deficit shrinkage (contrast trained: -180 deg2; GDD trained: -22 deg2, p< 0.001). In summary, motion perception is occasionally preserved in subacute CBs compared to chronic CBs. While GDD training may improve CS for motion, deliberate contrast training appears necessary to recover static CS.
Meeting abstract presented at VSS 2018
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