The Third Alexia

Df, Benson

doi:10.1001/archneur.1977.00500180021004

Cited by 77 publications

(20 citation statements)

References 12 publications

(1 reference statement)

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“…Paulesu et al (16) have reported underactivation in the insula in dyslexia, but Rumsey (17) and we find no support for this claim. Our findings implicating the IFG in developmental dyslexia are consonant with reports of acquired alexia accompanying some aphasias of the Broca type that have also involved this anterior region (37).…”

Section: Discussionsupporting

confidence: 91%

Functional disruption in the organization of the brain for reading in dyslexia

Shaywitz

Pugh

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

730

533

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Learning to read requires an awareness that spoken words can be decomposed into the phonologic constituents that the alphabetic characters represent. Such phonologic awareness is characteristically lacking in dyslexic readers who, therefore, have difficulty mapping the alphabetic characters onto the spoken word. To find the location and extent of the functional disruption in neural systems that underlies this impairment, we used functional magnetic resonance imaging to compare brain activation patterns in dyslexic and nonimpaired subjects as they performed tasks that made progressively greater demands on phonologic analysis. Brain activation patterns differed significantly between the groups with dyslexic readers showing relative underactivation in posterior regions (Wernicke's area, the angular gyrus, and striate cortex) and relative overactivation in an anterior region (inferior frontal gyrus). These results support a conclusion that the impairment in dyslexia is phonologic in nature and that these brain activation patterns may provide a neural signature for this impairment.Speech enables its users to create an indefinitely large number of words by combining and permuting a small number of phonologic segments, the consonants and vowels that serve as the natural constituents of the biologic specialization for language. An alphabetic transcription brings this same ability to readers but only as they connect its arbitrary characters (letters) to the phonologic segments they represent. Making that connection requires an awareness that all words, in fact, can be decomposed into phonologic segments. Thus, it is this awareness that allows the reader to connect the letter strings (the orthography) to the corresponding units of speech (phonologic constituents) that they represent. As numerous studies have shown, however, such awareness is largely missing in dyslexic children and adults (1-4). Not surprisingly, then, perhaps the most sensitive measure of the reading problem in dyslexia is inability to read phonologically legal nonsense words (5-7). As for why dyslexic readers should have exceptional difficulty developing phonologic awareness, there is support for the notion that the difficulty resides in the phonologic component of the larger specialization for language (8)(9)(10). If that component is imperfect, its representations will be less than ideally distinct and, therefore, harder to bring to conscious awareness.Previous efforts using functional imaging methods to examine brain organization in dyslexia have been inconclusive (11-17) largely, we think, because the experimental tasks tapped the several aspects of the reading process in somewhat unsystematic ways. Our aim therefore was to develop a set of hierarchically structured tasks that control the kind of language-relevant coding required, including especially the demand on phonologic analysis, and then to compare the performance and brain activation patterns (as measured by functional MRI) of dyslexic (DYS) and nonimpaired (NI) readers. Thus, procee...

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Section: Discussionsupporting

confidence: 91%

Functional disruption in the organization of the brain for reading in dyslexia

Shaywitz

Pugh

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

730

533

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“…Finally, we note that the left dorsolateral frontal lesion in Anderson et al's (1990) patient is not in a location we would ordinarily expect to produce impaired letter identification, although other reading impairments are sometimes associated with lesions in this general area (e.g., Benson, 1977;Berndt 8c Caramazza, 1980). In Starrfelt's (2007) case, the lesion locus was not identified.…”

Section: Discussionmentioning

confidence: 68%

Shared versus separate processes for letter and digit identification

McCloskey

Schubert

2014

Cognitive Neuropsychology

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Letters and digits, although similar in many respects, also differ in potentially significant ways. Most importantly, letters are elements of an alphabetic writing system, whereas digits are logographs. In this article, we explore whether letters and digits are identified by a single character identification process that makes no fundamental distinction between the two types of characters, or whether instead letter and digit identification processes diverge at least in some respects. We present evidence from an acquired dyslexic patient, L.H.D., who is impaired in both letter and digit identification. Working within a theoretical framework specifying the levels of representation implicated in letter identification, we systematically compare L.H.D.'s letter and digit processing. The results provide evidence that letter and digit identification implicate the same levels of representation, and further that L.H.D.'s identification errors for both letters and digits arise at the same point in processing. On the basis of these results, we argue for a shared process that mediates identification of both letters and digits. Finally, we discuss relevant previous results in light of this conclusion.

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“…24). Interestingly, there have been suggestions that at least some Broca's aphasics do exhibit a reading impairment, with one distinguishing feature being the relative inability to read single letters as compared with words (27)(28)(29). Unfortunately, neurological case descriptions of such Broca's aphasics have not systematically included measures of both word and nonword reading accuracy, and in some cases reading skills were assessed by using a measure of comprehension rather than pronunciation (e.g., point to the picture that matches a written word; ref.…”

Section: The Left Frontal Cortex and Phonological Dyslexiamentioning

confidence: 99%

Neuroimaging studies of word reading

Fiez

Petersen

1998

Proc. Natl. Acad. Sci. U.S.A.

655

381

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This review discusses how neuroimaging can contribute to our understanding of a fundamental aspect of skilled reading: the ability to pronounce a visually presented word. One contribution of neuroimaging is that it provides a tool for localizing brain regions that are active during word reading. To assess the extent to which similar results are obtained across studies, a quantitative review of nine neuroimaging investigations of word reading was conducted. Across these studies, the results converge to reveal a set of areas active during word reading, including left-lateralized regions in occipital and occipitotemporal cortex, the left frontal operculum, bilateral regions within the cerebellum, primary motor cortex, and the superior and middle temporal cortex, and medial regions in the supplementary motor area and anterior cingulate. Beyond localization, the challenge is to use neuroimaging as a tool for understanding how reading is accomplished. Central to this challenge will be the integration of neuroimaging results with information from other methodologies. To illustrate this point, this review will highlight the importance of spelling-to-sound consistency in the transformation from orthographic (word form) to phonological (word sound) representations, and then explore results from three neuroimaging studies in which the spelling-to-sound consistency of the stimuli was deliberately varied. Emphasis is placed on the pattern of activation observed within the left frontal cortex, because the results provide an example of the issues and benefits involved in relating neuroimaging results to behavioral results in normal and brain damaged subjects, and to theoretical models of reading.Reading is one of the most important skills we learn, and not surprisingly it has been the focus of many investigations across a range of methodologies, including behavioral studies in normal subjects, computational modeling, and neuropsychological assessment of patients with acquired brain damage. This review discusses the contributions that neuroimaging can make to this interdisciplinary effort, with a focus on one aspect of skilled reading: the ability to pronounce a visually presented word.In the most general sense, neuroimaging provides a tool for localizing and measuring the activity of brain regions that are recruited during the performance of a cognitive task in normal subjects. The value of this contribution will be explored in the context of two questions. The first is whether the method is reliable. In other words, if the same task is studied by two different investigators, do they localize the same brain regions? Clearly, the utility of a method in which the results fail to converge across studies must be seriously questioned. The first section addresses this issue by evaluating the regions of activation reported across nine neuroimaging studies of word reading.However, just being reliable does not make a method worthwhile. A second question is whether the information gained from neuroimaging yields important insigh...

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The Third Alexia

Cited by 77 publications

References 12 publications

Functional disruption in the organization of the brain for reading in dyslexia

Functional disruption in the organization of the brain for reading in dyslexia

Shared versus separate processes for letter and digit identification

Neuroimaging studies of word reading

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