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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

Authors

Cristiana Cavina-Pratesi

A. David Milner

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.

Journal Article Type Article
Publication Date Mar 1, 2015
Journal Cortex
Print ISSN 0010-9452
Electronic ISSN 1973-8102
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 64
Issue March
Pages 29-46
Institution Citation Large, M., 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). doi:10.1016/j.cortex.2014.09.017. ISSN 0010-9452
DOI https://doi.org/10.1016/j.cortex.2014.09.017
Keywords Visual form agnosia; fMRI; Ventral stream; Word recognition; VWFA
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.sciencedirec...e/pii/S0010945214003086

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