Jason Barton

University of British Columbia, Vancouver, Canada



Sheldon, C. A., Abegg, M., Sekunova, A., & Barton, J. J. (2012). The word-length effect in acquired alexia, and real and virtual hemianopia. Neuropsychologia, 50, 841-851.






Selected references on alexia


Sheldon, C. A., Abegg, M., Sekunova, A., & Barton, J. J. (2012). The word-length effect in acquired alexia, and real and virtual hemianopia. Neuropsychologia, 50, 841-851.
Notes: A word-length effect is often described in pure alexia, with reading time proportional to the number of letters in a word. Given the frequent association of right hemianopia with pure alexia, it is uncertain whether and how much of the word-length effect may be attributable to the hemifield loss. To isolate the contribution of the visual field defect, we simulated hemianopia in healthy subjects with a gaze-contingent paradigm during an eye-tracking experiment. We found a minimal word-length effect of 14ms/letter for full-field viewing, which increased to 38ms/letter in right hemianopia and to 31ms/letter in left hemianopia. We found a correlation between mean reading time and the slope of the word-length effect in hemianopic conditions. The 95% upper prediction limits for the word-length effect were 51ms/letter in subjects with full visual fields and 161ms/letter with simulated right hemianopia. These limits, which can be considered diagnostic criteria for an alexic word-length effect, were consistent with the reading performance of six patients with diagnoses based independently on perimetric and imaging data: two patients with probable hemianopic dyslexia, and four with alexia and lesions of the left fusiform gyrus, two with and two without hemianopia. Two of these patients also showed reduction of the word-length effect over months, one with and one without a reading rehabilitation program. Our findings clarify the magnitude of the word-length effect that originates from hemianopia alone, and show that the criteria for a word-length effect indicative of alexia differ according to the degree of associated hemifield loss
Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada

Barton, J. J., Fox, C. J., Sekunova, A., & Iaria, G. (2010). Encoding in the visual word form area: an fMRI adaptation study of words versus handwriting. Journal of Cognitive Neuroscience, 22, 1649-1661.
Notes: Written texts are not just words but complex multidimensional stimuli, including aspects such as case, font, and handwriting style, for example. Neuropsychological reports suggest that left fusiform lesions can impair the reading of text for word (lexical) content, being associated with alexia, whereas right-sided lesions may impair handwriting recognition. We used fMRI adaptation in 13 healthy participants to determine if repetition-suppression occurred for words but not handwriting in the left visual word form area (VWFA) and the reverse in the right fusiform gyrus. Contrary to these expectations, we found adaptation for handwriting but not for words in both the left VWFA and the right VWFA homologue. A trend to adaptation for words but not handwriting was seen only in the left middle temporal gyrus. An analysis of anterior and posterior subdivisions of the left VWFA also failed to show any adaptation for words. We conclude that the right and the left fusiform gyri show similar patterns of adaptation for handwriting, consistent with a predominantly perceptual contribution to text processing
University of British Columbia, Vancouver, Canada. jasonbarton@shaw.ca

Barton, J. J., Sekunova, A., Sheldon, C., Johnston, S., Iaria, G., & Scheel, M. (2010). Reading words, seeing style: the neuropsychology of word, font and handwriting perception. Neuropsychologia, 48, 3868-3877.
Notes: The reading of text is predominantly a left hemisphere function. However, it is also possible to process text for attributes other than word or letter identity, such as style of font or handwriting. Anecdotal observations have suggested that processing the latter may involve the right hemisphere. We devised a test that, using the identical stimuli, required subjects first to match on the basis of word identity and second to match on the basis of script style. We presented two versions, one using various computer fonts, and the other using the handwriting of different individuals. We tested four subjects with unilateral lesions who had been well characterized by neuropsychological testing and structural and/or functional MRI. We found that two prosopagnosic subjects with right lateral fusiform damage eliminating the fusiform face area and likely the right visual word form area were impaired in completion times and/or accuracy when sorting for script style, but performed better when sorting for word identity. In contrast, one alexic subject with left fusiform damage showed normal accuracy for sorting by script style and normal or mildly elevated completion times for sorting by style, but markedly prolonged reading times for sorting by word identity. A prosopagnosic subject with right medial occipitotemporal damage sparing areas in the lateral fusiform gyrus performed well on both tasks. The contrast in the performance of patients with right versus left fusiform damage suggests an important distinction in hemispheric processing that reflects not the type of stimulus but the nature of processing required
Department of Medicine (Neurology), University of British Columbia, Vancouver, British Columbia, Canada. jasonbarton@shaw.ca

Barton, J. J. (2004). Visual dysfunction. In M.Rizzo & P. J. Eslinger (Eds.), Principles and practice of behavioral neurology and neuropsychology (pp. 267-289). Philadelphia,PA: Saunders.

Behrmann, M., Shomstein, S. S., Black, S. E., & Barton, J. J. (2001). The eye movements of pure alexic patients during reading and nonreading tasks. Neuropsychologia, 39, 983-1002.
Notes: Department of Psychology, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA. behrmann+@cmu.edu
We compared the eye-movements of two patients who read letter-by-letter (LBL) following a left occipital lobe lesion with those of normal control subjects and of hemianopic patients in two tasks: a nonreading visual search task and a text reading task. Whereas the LBL readers exhibited similar eye-movement patterns to those of the other two groups on the nonreading task, their eye movements differed significantly during reading, as reflected in the disproportionate increase in the number and duration of fixations per word and in the regressive saccades per word. Importantly, relative to the two control groups, letter-by-letter readers also made more fixations per word as word length increased, especially as word frequency and word imageability decreased. Two critical results emerged from these experiments: First, the alteration in the oculomotor behavior of the LBL readers during reading is similar to that seen in normal readers under difficult reading conditions, as well as in beginning readers and in those with developmental dyslexia, and appears to reflect difficulties in processing the visual stimulus. Second, the interaction of length with frequency and with imageability in determining the eye movement pattern is consistent with an interactive activation model of normal word recognition in which weakened activation of orthographic input can nevertheless engage high-level lexical factors


Anders Gade