December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
Neurochemistry in hMT+ underlies residual vision in visual loss after stroke
Author Affiliations & Notes
  • Hanna E. Willis
    Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom, OX3 9DU
  • I. Betina Ip
    Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom, OX3 9DU
  • Archie Watt
    Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom, OX3 9DU
  • Saad Jbabdi
    Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom, OX3 9DU
  • William Clarke
    Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom, OX3 9DU
  • Matthew R. Cavanaugh
    Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA
  • Krystel R. Huxlin
    Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA
  • Kate E. Watkins
    Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom, OX2 6GG
  • Marco Tamietto
    Department of Psychology, University of Torino, 10123 Torino, Italy
  • Holly Bridge
    Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom, OX3 9DU
  • Footnotes
    Acknowledgements  The work was funded by the European Research Council, British Medical Associaton Foundation, Medical Research Council UK and a Waverley Scholarship from The Queen’s College, Oxford, UK.
Journal of Vision December 2022, Vol.22, 3990. doi:https://doi.org/10.1167/jov.22.14.3990
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      Hanna E. Willis, I. Betina Ip, Archie Watt, Saad Jbabdi, William Clarke, Matthew R. Cavanaugh, Krystel R. Huxlin, Kate E. Watkins, Marco Tamietto, Holly Bridge; Neurochemistry in hMT+ underlies residual vision in visual loss after stroke. Journal of Vision 2022;22(14):3990. https://doi.org/10.1167/jov.22.14.3990.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Damage to the primary visual cortex due to a stroke leads to visual loss in the contralateral visual fields. Many patients show spared visual processing abilities in the blind field, which has been linked to preserved activity in ipsilesional hMT+. Although hMT+ is known to be important for residual visual processing, it remains unclear how the functioning of hMT+ facilitates this residual vision. In this study, we explored the relationship between residual vision, fMRI activity and in vivo concentrations of neurotransmitters GABA and glutamate through GABA-edited MR Spectroscopy (MRS) in ipsilesional hMT+. Nineteen participants with visual loss after stroke (6 female; aged 24-74 years; >6 months post-stroke) were recruited. A 2AFC high-contrast Gabor detection task (diameter=5°, stimulus-duration=500ms, stimulus-contrast=50% and 100%; spatial-frequency=1cyl/°, temporal-frequency=10Hz), presented in the perimetrically-defined blind-fields, was used to measure residual vision. Resting MRS was used to quantify GABA+ (GABA+macromolecules) and Glx (glutamate, glutamine and glutathione) relative to creatine (Cr) in voxels (25x25x20mm) in ipsilesional hMT+ and primary motor cortex (M1; control region). Functional MRI was used to calculate percentage BOLD signal change in hMT+ during passive viewing of the high-contrast Gabor stimuli detailed earlier in the perimetrically-defined blind field. Reduced concentrations of GABA+ and Glx in the hMT+ voxel were related to improved performance on the contrast detection task, even when controlling for grey matter volume, age and time since lesion (GABA+: R2=0.41; p=0.012; Glx: R2=0.53; p=0.003). In contrast, there was no relationship between residual vision and BOLD signal in ipsilesional hMT+ (R2=-0.06, p=0.884), or GABA (R2=0.25, p=0.976) and Glx (R2=0.12, p=0.981) in M1. Resting neurochemistry in hMT+ reflects residual vision in patients with stroke-induced visual loss better than visually driven BOLD signals. Decreased inhibitory GABA+ and excitatory Glx levels may reflect a greater capacity for plasticity in these patients, facilitating improved performance, whilst preserving an excitatory-inhibitory balance.

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