title: How low can you go: spatial frequency sensitivity in a patient with pure alexia.
abstract: Pure alexia is a selective deficit in reading, following lesions to the posterior left hemisphere. Writing and other language functions remain intact in these patients. Whether pure alexia is caused by a primary problem in visual perception is highly debated. A recent hypothesis suggests that a low level deficit - reduced sensitivity to particular spatial frequencies - is the underlying cause. We tested this hypothesis in a pure alexic patient (LK), using a sensitive psychophysical paradigm to examine her performance with simple patterns of different spatial frequency. We find that both in a detection and a classification task, LK's contrast sensitivity is comparable to normal controls for all spatial frequencies. Thus, reduced spatial frequency sensitivity does not constitute a general explanation for pure alexia, suggesting that the core deficit in this disorder is at a higher level in the visual processing stream.
authors.affiliation: Center for Visual Cognition, Department of Psychology, University of Copenhagen, Denmark. randi.starrfelt@psy.ku.dk
authors.forename: Randi
authors.initials: R
authors.lastname: Starrfelt
authors.forename: Simon
authors.initials: S
authors.lastname: Nielsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Habekost
authors.forename: Tobias S
authors.initials: TS
authors.lastname: Andersen
mesh_terms: D000328:Adult; D020237:Alexia, Pure / Q000209:etiology / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D011932:Reading
keywords: Case study; Contrast sensitivity; LBL-reading; Pure alexia; Spatial frequency sensitivity; Word length effect; Word reading