H. Branch Coslett

Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.







Selected references on reading and alexia

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.



Anders Gade