Visual processing of words in a patient with visual form agnosia: A behavioural and fMRI study

Large, Mary-Ellen; Cavina-Pratesi, Cristiana; Milner, A. David

Abstract

Patient D.F. has a profound and enduring visual form agnosia due to a carbon monoxide poisoning episode suffered in 1988. Her inability to distinguish simple geometric shapes or single alphanumeric characters can be attributed to a bilateral loss of cortical area LO, a loss that has been well established through structural and functional fMRI. Yet despite this severe perceptual deficit, D.F. is able to “guess” remarkably well the identity of whole words. This paradoxical finding, which we were able to replicate more than 20 years following her initial testing, raises the question as to whether D.F. has retained specialized brain circuitry for word recognition that is able to function to some degree without the benefit of inputs from area LO. We used fMRI to investigate this, and found regions in the left fusiform gyrus, left inferior frontal gyrus, and left middle temporal cortex that responded selectively to words. A group of healthy control subjects showed similar activations. The left fusiform activations appear to coincide with the area commonly named the visual word form area (VWFA) in studies of healthy individuals, and appear to be quite separate from the fusiform face area. We hypothesize that there is a route to this area that lies outside area LO, and which remains relatively unscathed in D.F.

Citation

Large, M.-E., Cavina-Pratesi, C., & Milner, A. D. (2015). Visual processing of words in a patient with visual form agnosia: A behavioural and fMRI study. Cortex; a journal devoted to the study of the nervous system and behavior, 64(March), 29-46. https://doi.org/10.1016/j.cortex.2014.09.017

• Journal Article Type: Article
• Acceptance Date: Sep 26, 2014
• Online Publication Date: Oct 8, 2014
• Publication Date: Mar 1, 2015
• Deposit Date: May 13, 2015
• Publicly Available Date: May 13, 2015
• Journal: Cortex
• Print ISSN: 0010-9452
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 64
• Issue: March
• Pages: 29-46
• DOI: https://doi.org/10.1016/j.cortex.2014.09.017
• Keywords: Visual form agnosia; fMRI; Ventral stream; Word recognition; VWFA
• Public URL: https://hull-repository.worktribe.com/output/373853
• Publisher URL: http://www.sciencedirect.com/science/article/pii/S0010945214003086
• Additional Information: Author's accepted manuscript of article published in: Cortex, 2015, v.64 at http://www.sciencedirect.com/science/article/pii/S0010945214003086
• Contract Date: May 13, 2015