Andersen, Tobias

Habekost, T.

Nielsen, S.

Starrfelt, Randi

Objective: Pure alexia is a seemingly selective deficit in reading, follow- ing focal lesions to the posterior left hemisphere. The hallmark feature of pure alexia is a word length effect in single word reading, where reaction times may increase with hundreds of milliseconds per additional letter in a word. Other language functions, including writing, are intact. It has been suggested that pure alexia is caused by a general deficit in visual processing, one that affects reading disproportionally compared to other visual stimuli. The most concrete hypothesis to date suggests that pure alexia is caused by a lack of sensitivity to particular spatial frequencies (e.g., Fiset et al., 2006), and that this results in the characteristic word length effect, as well as effects of letter confusability on reading times. Participants and Methods: We have tested this hypothesis in a patient with pure alexia (LK). LK shows significant effects of word length and letter confusability on reaction times in single word reading, while her writing and other language skills are intact. In two experiments, we in- vestigate LK’s performance with simple patterns of different spatial fre- quency (Gabor patches), and compare this to normal controls.Results: We find that both in a detection and a classification para- digm, LK shows normal sensitivity for all spatial frequencies. Conclusions: On this basis we conclude that neither the word length effect, nor the effect of letter confusability on reading times, can be ex- plained by a lack of sensitivity to particular spatial frequencies. Thus, the explanation for the reading performance of patients with pure alexia is likely to be found at a higher level of processing.<br/

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 20, 2017How Low Can You Go: Spatial Frequency Sensitivity in Pure AlexiaStarrfelt, Randi; Nielsen, S.; Habekost, T.; Andersen, TobiasPublication date:2012Link back to DTU OrbitCitation (APA):Starrfelt, R., Nielsen, S., Habekost, T., & Andersen, T. (2012). How Low Can You Go: Spatial FrequencySensitivity in Pure Alexia. Abstract from 2012 International Neuropsychological Society Mid-Year Meeting/11thNordic Meeting in Neuropsychology, Oslo, Norway.R. STARRFELT, S. NIELSEN, T. HABEKOST & T. ANDERSEN. How Low Can You Go: Spatial Frequency Sensitivity in Pure Alexia. Objective: Pure alexia is a seemingly selective deficit in reading, follow- ing focal lesions to the posterior left hemisphere. The hallmark feature of pure alexia is a word length effect in single word reading, where reaction times may increase with hundreds of milliseconds per additional letter in a word. Other language functions, including writing, are intact. It has been suggested that pure alexia is caused by a general deficit in visual processing, one that affects reading disproportionally compared to other visual stimuli. The most concrete hypothesis to date suggests that pure alexia is caused by a lack of sensitivity to particular spatial frequencies (e.g., Fiset et al., 2006), and that this results in the characteristic word length effect, as well as effects of letter confusability on reading times.  Participants and Methods: We have tested this hypothesis in a patient with pure alexia (LK). LK shows significant effects of word length and letter confusability on reaction times in single word reading, while her writing and other language skills are intact. In two experiments, we in- vestigate LK’s performance with simple patterns of different spatial fre- quency (Gabor patches), and compare this to normal controls. Results: We find that both in a detection and a classification para- digm, LK shows normal sensitivity for all spatial frequencies. Conclusions: On this basis we conclude that neither the word length effect, nor the effect of letter confusability on reading times, can be ex- plained by a lack of sensitivity to particular spatial frequencies. Thus, the explanation for the reading performance of patients with pure alexia is likely to be found at a higher level of processing. Correspondence: Randi Starrfelt, Ph.D., Department of Psychology, Uni- versity of Copenhagen, O. Farimagsgade 2a, Copenhagen K DK-1353, Denmark. E-mail: randi.starrfelt@psy.ku.dk Presented at The 2012 International Neuropsychological Society Mid-Year Meeting/11th Nordic Meeting in Neuropsychology June 27-30, 2012 O slo, Norway  

How Low Can You Go: Spatial Frequency Sensitivity in Pure Alexia

http://orbit.dtu.dk/ws/files/74190746/prod11387268636654.StarrfeltNielsenHabekostAndersen12.pdf

How Low Can You Go: Spatial Frequency Sensitivity in Pure Alexia

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology