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Melissa Polonenko, Krystel Huxlin, Ross Maddox; Auditory spatial discrimination in chronic hemianopes. Journal of Vision 2020;20(11):557. doi: https://doi.org/10.1167/jov.20.11.557.
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© ARVO (1962-2015); The Authors (2016-present)
Stroke damage to the primary visual cortex (V1) causes blindness in the contralateral hemifield, known as hemianopia. We are interested to see if it also affects abilities beyond visual perception. The auditory and visual systems are highly interconnected, although mechanisms of multisensory perception are not well understood in the context of adult-onset, visual cortical damage. Neuroplastic changes following visual deficits may impair, enhance or have no effect on auditory spatial processing. This in turn, has implications for designing multisensory, perceptual training paradigms that are intended to recover vision in hemianopic fields. Here, we investigated the impact of adult-onset, stroke-induced V1 damage on auditory spatial discrimination in 17 hemianopes (mean±SD age 57.5±13.5 years, 22.6±18.7 months post stroke). Goldmann perimetry measured the size of the patients’ residual visual field as ranging from 6,884 to 14,678 deg² (11,074±2,372 deg²). Auditory performance in hemianopes was compared to that of 14 age-matched, visually-intact controls (55.2±12.0 years). While fixating straight ahead, subjects heard two, sequentially-presented sounds localized (virtually over headphones) symmetrically about a reference azimuth. They were asked whether the second sound was to the left or right of the first sound. Two reference azimuths (20° and 40°) were tested in both hemifields for a total of four conditions. Overall, separation thresholds were better for the 20° than 40° condition (p=0.036) but similar between hemifields (p=0.53) and subject groups (p=0.38). The differences in thresholds between blind and sighted hemifields in hemianopes were not more variable than expected from control subjects, and auditory discrimination did not correlate with the size of the visual defects. Therefore, large visual deficits from V1 damage sustained in adulthood do not appear to impact relative auditory localization. This intact auditory processing has the potential to be harnessed for new, multisensory, perceptual training strategies to help hemianopes regain vision in their blind fields.
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