September 2019
Volume 19, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2019
A Rare Visuospatial Disorder
Author Affiliations & Notes
  • Aimee K Dollman
    Department of Psychology, University of Cape Town
  • Mark L Solms
    Department of Psychology, University of Cape Town
Journal of Vision September 2019, Vol.19, 57. doi:
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      Aimee K Dollman, Mark L Solms; A Rare Visuospatial Disorder. Journal of Vision 2019;19(10):57.

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

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Cases with visuospatial abnormalities provide opportunities for understanding the underlying cognitive mechanisms. Three cases of visual mirror-reversal have been reported: AH (McCloskey, 2009), TM (McCloskey, Valtonen, & Sherman, 2006) and PR (Pflugshaupt et al., 2007). We report a fourth case, BS -- with focal occipital cortical dysgenesis -- who displays highly unusual visuospatial abnormalities. She initially produced mirror reversal errors similar to those of AH, who -- like our patient -- showed a selective developmental deficit. On further examination, it became apparent that BS differed from AH in significant respects. A detailed study followed which: (1) comprehensively documented BS’s disorder, (2) determined the ways in which it differed from that of AH, and (3) compared it to other similar disorders reported in the literature. Extensive examination of BS revealed the following phenomena: mirror reversal errors (sometimes affecting only parts of the visual fields) in both horizontal and vertical planes; subjective representation of visual objects and words in distinct left and right visual fields; subjective duplication of objects of visual attention (not due to diplopia); uncertainty regarding the canonical upright orientation of everyday objects; mirror reversals during saccadic eye movements on oculomotor tasks; failure to integrate visual with other sensory inputs (e.g., she feels herself moving backwards when visual information shows she is moving forward). Fewer errors are produced under conditions of certain visual variables. These and other findings have led us to conclude that BS draws upon a subjective representation of visual space that is structured phenomenally much as it is anatomically in early visual cortex (i.e., rotated through 180 degrees, split into left and right fields, etc.). Despite this, BS functions remarkably well in her everyday life, apparently due to extensive compensatory mechanisms deployed at higher (executive) processing levels beyond the visual modality.

Acknowledgement: National Research Foundation, UCT Doctoral Research Scholarship, Harry Crossley Postgraduate Scholarship 

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