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Elizabeth Saionz; Different properties of training-induced visual recovery in sub-acute and chronic stroke patients. Journal of Vision 2017;17(15):30-31. doi: 10.1167/17.15.30a.
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© ARVO (1962-2015); The Authors (2016-present)
Stroke damage to V1 in adult humans causes cortical blindness (CB). We previously showed that visual discrimination training in chronic (>6 months) stroke patients decreases the deficit, but recovered vision remains impaired. Evidence in sensorimotor stroke suggests that earlier intervention promotes greater recovery. Here, we asked if visual discrimination training initiated sub-acutely (<3 months) after V1 stroke enhances improvement in CB. Ten sub-acute and 12 chronic CB patients trained with a global direction discrimination and integration task in their blind field. Three additional sub-acutes were tested but not trained, serving as controls. Initial discrimination performance was at chance (baseline normalized direction range [NDR] thresholds=100% for all subjects). After daily home training for 3 months, sub-acutes attained normal NDR thresholds (30 ± 14%) at trained locations much faster than chronics (sub-acutes: 11 ± 14 sessions; chronics: 99 ± 65 sessions; t(20)=4.18, p<0.001). Moreover, unlike chronics, whose recovery never transferred deeper into the blind field, trained sub-acutes exhibited transfer of recovery up to 10° deeper into the blind field than trained locations. Untrained sub-acutes had no spontaneous improvement in NDR, though all sub-acutes improved similarly on clinical Humphrey perimetry (luminance detection). Thus, discrimination training initiated in sub-acute CBs generates faster, more spatially distributed discrimination improvements than identical training in chronic CBs. While detection perimetry improved in both trained and untrained sub-acutes, only trained subjects recovered discrimination performance. In summary, without an intact V1, luminance detection may improve spontaneously during the sub-acute period, but deliberate training is required to recover visual discrimination abilities.
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