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Turkeltaub, P. E., Goldberg, E. M., Postman-Caucheteux, W. A., Palovcak, M.,
Quinn, C., Cantor, C. et al. (2013). Alexia due to ischemic stroke of the
visual word form area. Neurocase, in press
Notes: The visual word form area (VWFA) is a region in the posterior left
occipitotemporal cortex adjacent to the fusiform gyrus hypothesized to
mediate word recognition. Evidence supporting the role of this area in
reading comes from neuroimaging studies of normal subjects, case-controlled
lesion studies, and studies of patients with surgical resection of the VWFA
for tumors or epilepsy. Based on these prior reports, a small discrete
lesion to the VWFA would be expected to cause alexia in a literate person
without prior brain process, but such a case has not previously been
reported to our knowledge. Here, we report the case of a previously-healthy
63-year-old man with the acute onset of alexia without other significant
impairments. Magnetic resonance imaging (MRI) of the brain revealed a small
ischemic stroke localized to the inferior left occipitotemporal cortex,
corresponding to the approximate location of the putative VWFA.
Characteristic of pure alexia, testing in the weeks following the stroke
revealed a letter-by-letter reading strategy and a word length effect on
single word reading. Formal visual field testing was normal. There was no
color anomia, or object or face recognition deficits, although a mild
agraphia may have been present. This case of acute-onset alexia in a
previously normal individual due to a small stroke restricted to the VWFA
and sparing occipital cortex and white matter pathways supports the
conclusion that the VWFA is crucial for reading
Coslett, H. B. (2012). Acquired dyslexia. In K.M.Heilman & E. Valenstein
(Eds.), Clinical neuropsychology (5 ed., pp. 115-129). New York:
Oxford University Press.
Coslett, H. B. & Saffran, E. M. (2001). Peripheral dyslexias. In M.Behrmann
(Ed.), Handbook of neuropsychology, Vol. 4.
Disorders of visual behavior
(2 ed., pp. 207-214). Amsterdam: Elsevier.
Coslett, H. B. (2000). Acquired dyslexia. Seminars in Neurology, 20,
419-426.
Notes: Department of Neurology, Temple University School of Medicine,
Philadelphia, Pennsylvania, USA
Disorders of reading are frequently encountered in patients with acquired
cerebral lesions. Investigations in the past few decades have improved our
understanding of these disorders. In this article we review the peripheral
dyslexias, including neglect dyslexia, attentional dyslexia, and pure alexia
(or alexia without agraphia), as well as the "central" dyslexias, including
deep, surface, and phonological dyslexia. Current accounts of acquired
dyslexia are also discussed. Finally, we briefly describe the reading tasks
that serve to differentiate the different reading disorders
Buxbaum, L. J., Glosser, G., & Coslett, H. B. (1999). Impaired face and word
recognition without object agnosia. Neuropsychologia, 37, 41-50.
Notes: Moss Rehabilitation Research Institute, Temple University Hospital,
Philadelphia, PA 19141, USA. LBuxbaum@aehn2.einstein.edu ; ABSTRACT: A
leading account of high-level visual recognition proposes that the
recognition of faces, objects, and words is mediated by two processing
capacities. Words are assumed to require the capacity to represent numerous
parts, whereas faces are processed wholistically. and hence require the
representation of complex units. Object recognition requires the capacity to
represent both numerous and complex parts. As object recognition depends
upon the same processing capacities underlying face and word recognition,
this account predicts that patients with severe alexia and prosopagnosia
should be deficient in tests of object recognition. We report a patient who
is unable to recognize words or faces, yet performs relatively well on tests
of object recognition. The two-capacity theory cannot accommodate this
pattern of performance without additional assumptions
Saffran, E. M. & Coslett, H. B. (1998). Implicit vs. letter-by-letter
reading in pure alexia: A tale of two systems. Cognitive Neuropsychology,
15, 141-165.
Notes: Recent studies of pure alexia present a contradictory picture.
Despite evidence of impaired letter identification in letter-by- letter
readers, some patients are able to carry out lexical decision and other
tasks under conditions of rapid presentation, although they are seldom able
to identify these stimuli explicitly. We review evidence for both facets of
pure alexic performance and offer an account of this pattern in terms of
right- and left-hemisphere reading mechanisms. Specifically, we suggest that
the right hemisphere supports performance in covert reading tasks, and that
letter-by-letter reading is the product of the left hemisphere, operating on
information transmitted from the right.
Coslett, H. B. (1997). Acquired dyslexia. In T.E.Feinberg & M. J. Farah
(Eds.), Behavioral neurology and neuropsychology (pp. 197-208). New
York: McGraw-Hill.
Buxbaum, L. J. & Coslett, H. B. (1996). Deep dyslexic phenomena in a
letter-by-letter reader. Brain and Language, 54, 136-167.
Notes: Moss Rehabilitation Research Institute, Philadelphia, PA 19141, USA.
Buxbaum@shrsys.hslc.org Numerous accounts of pure alexia have suggested that
prelexical impairment precludes rapid access to orthographic information in
patients with the disorder. We report a patient with features of both pure
and partially recovered deep dyslexia in whom we demonstrate prelexical
deficits in maintaining a reliable abstract representation of the right side
of letter arrays, as well as in modulating a "spotlight" of visual
attention. These deficits, we suggest, encourage the patients's use of a
letter-by- letter reading strategy; despite them, however, he demonstrates
rapid, accurate reading of some, but not all classes of words. Furthermore,
the patient's reading is influenced by both prelexical and lexical-semantic
factors such that speed and accuracy are optimal for high imagiability nouns
of few letters. Finally, the patient accurately names orally spelled words
of all classes. Taken together, these data are consistent with the
hypothesis that rapid reading may be enabled by lexical-semantic support
from a right hemisphere-mediated processing system which recognizes words as
whole, thereby mitigating the effect of the prelexical deficits
Coslett, H. B. & Saffran, E. M. (1994). Mechanisms of implicit reading in
alexia. In M.J.Farah & G. Ratcliff (Eds.), The neuropsychology of
high-level vision. Collected tutorial essays (pp. 299-330).
Hillsdale,NJ: Erlbaum.
Coslett, H. B. & Monsul, N. (1994). Reading with the right hemisphere:
evidence from transcranial magnetic stimulation. Brain and Language, 46,
198-211.
Notes: AD: Department of Neurology, Temple University School of Medicine,
Philadelphia, PA AB: Although many patients with dominant hemisphere damage
retain some reading ability, the anatomic substrate of the preserved reading
remains controversial. We tested the hypothesis that the right hemisphere
mediates the reading of some patients with acquired dyslexia by using
Transcranial Magnetic Stimulation (TMS) to assess the effect of transient
cortical stimulation on reading. A patient with (partially recovered) pure
alexia was asked to read aloud briefly presented words, half of which were
shown in association with TMS of the right or left hemisphere. Consistent
with the right hemisphere reading hypothesis, stimulation of the right but
not the left hemisphere disrupted oral reading
Coslett, H. B., Saffran, E. M., Greenbaum, S., & Schwartz, H. (1993).
Reading in pure alexia. The effect of strategy. Brain, 116, 21-37.
Notes: Department of Neurology, Temple University, Philadelphia, PA A number
of investigators have demonstrated that patients with pure alexia comprehend
briefly presented words which they are unable to explicitly identify. We
suggested previously that these patients may read by means of two distinct
procedures: a laborious letter-by-letter method and a 'whole-word' procedure
which, at least initially, does not support explicit word identification. We
report a test of this proposal in a patient with pure alexia. We reasoned
that if the patient had access to two distinct and incompatible procedures,
he might be induced to switch from one to the other by changing task
demands. We found that when instructed to name words, the patient employed a
letter- by-letter strategy; in contrast, when instructed to make lexical
decision or semantic judgements about rapidly presented words, he appeared
to use a 'whole-word' strategy. These data support the hypothesis that two
distinct procedures are available to this patient. We argue, further, that
is necessary to suppress use of the letter-by-letter strategy to demonstrate
whole word reading capability in pure alexics, and that failure to do so may
account for negative findings in other cases reported in the literature
Coslett, H. B. & Saffran, E. M. (1989). Evidence for preserved reading in
'pure alexia'. Brain, 112, 327-359.
Notes: We describe 4 patients who developed pure alexia after infarctions of
the left cerebral hemisphere. All subjects employed a letter-by-letter
strategy (with varying degrees of success) to explicitly identify visually
presented words. Although all 4 subjects explicitly denied that they could
identify briefly presented words, they all performed significantly better
than chance on lexical decision and forced- choice semantic categorization
tasks with briefly presented words which they could not explicitly identify.
Three subjects regained the ability to explicitly identify briefly presented
words; these subjects were more accurate with nouns than functors and words
of high as compared with low imageability. Additionally, these subjects were
impaired in the processing of suffixes. These data are not accommodated by
the 'disconnection' account of pure alexia but are more consistent with the
hypothesis that reading in these patients is mediated by the right
hemisphere
Coslett, H. B., Gonzalez Rothi, L., & Heilman, K. M. (1985). Reading:
dissociation of the lexical and phonologic mechanisms. Brain and
Language, 24, 20-35.
Notes: Three distinct reading mechanisms have been proposed: the phonologic
conversion system in which letters are converted to their sound equivalents
(phonemes) before meaning is established, and two lexical or whole-word
mechanisms in which a word (or root morpheme) is identified as a single unit
rather than by phonologic conversion. The two lexical mechanisms differ in
that one is inextricably linked to semantics but the other is not. The
phonologic conversion system may depend more on the perisylvian phonologic
system than do the lexical mechanisms, which may be mediated by left
parietal or occipital areas or by the right hemisphere. Described here is a
patient who had an infarction that partially isolated the perisylvian speech
areas and disconnected the partially preserved lexical systems from the
phonologic mechanism. He read visually presented orthographically irregular
words but could not pronounce orally spelled irregular words. Although he
could not read nonwords, he could pronounce orally spelled nonwords and
orthographically regular words. These observations suggest that the lexical
and phonologic conversion systems are functionally and anatomically
distinct.
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