Visual perception supported by verbal mediation in an individual with cerebral visual impairment (CVI)

Abstract

Cerebral visual impairment (CVI) often presents with deficits associated with higher order visual processing. We report a case of an individual with CVI who uses a verbal mediation strategy to perceive and interact with his visual surroundings. Visual perceptual performance was assessed using a virtual reality based visual search task combined with eye tracking. Functional magnetic resonance imaging (fMRI) was employed to identify the neural correlates associated with this strategy. We found that when using verbal mediation, the individual could readily detect and track the target within the visual scene which was associated with robust activation within a network of occipito-parieto-temporal visual cortical areas. In contrast, when not using verbal mediation, the individual was completely unable to perform the task, and this was associated with dramatically reduced visual cortical activation. This unique compensatory strategy may be related to the individual's use of verbal working memory for the purposes of understanding complex visual information.

Keywords: Cerebral visual impairment; Higher order processing; Verbal mediation; Visual impairment; fMRI.