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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
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