Acquired aphasia in children and the ontogenesis of hemispheric functional specialization.
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The performance of five aphasics with agraphia and right hemiplegia showing side differences in writing to dictation is reported on. It was found that writing with the paralyzed arm, supported by a writing aid, was better than writing with the left hand. In a control group of aphasics with agraphia, but without hemiplegia, such side differences were not found. The conclusion is drawn that in aphasia with hemiplegia the lesions intersect the path between the graphic region of the dominant hemisphere and the corpus callosum. Therefore the observed syndrome is termed "Graphic Disconnection Syndrome."
Most right-handed crossed aphasics are not apractic. They usually have agraphia characterized by misspellings but retain the ability to write well-formed graphemes. We describe a right-handed patient with a right parietal lesion who was aphasic and not apractic. He was unable to write any formed graphemes despite a relatively preserved ability to spell aloud. We postulate that praxis and writing are dissociated in this patient because the motor engrams for praxis were located in his left hemisphere and the engrams for writing were in his right hemisphere. In addition, he comprehended commands for limb motor activities (praxis) far better than he comprehended other speech. This suggests that in this patient the areas used to comprehend limb motor commands may be anatomically distinct from areas important in comprehending other aspects of speech.
The purpose of this study was to investigate the nature of the written spelling deficit manifested by Broca's aphasics. Four spelling tests were given to eight Broca's aphasic patients. Analysis of misspelling errors led the investigators to conclude that Broca's aphasics do not spell phonically, but rather adhere exclusively to a visual/orthographic strategy. Possible cognitive deficits underlying the spelling problem are identified. The written spelling deficit is related to other features of the syndrome of Broca's aphasia, and finally, speculations are offered concerning the neurological substrate of written spelling in Broca's aphasic patients.
Two experiments show that the spelling of a nonword that is heard (i.e., /prein/) is influenced by the spelling of a word that is heard earlier (i.e., "brain" greater than prain and "crane" greater than prane). This is a robust effect and inspection of the pattern of results suggests that, under these conditions, both words and nonwords are lexically analyzed. A patient with an aquired reading disorder characterized as surface dyslexia was unaffected by such lexical influences in his spelling of nonwords. Moreover, his spelling suggested a defective ability to generate phonemically acceptable spellings of nonwords. Taken together with other reports of neurologically caused spelling impairments these results suggest that skill at assigning letters to sounds never becomes independent of lexical skill in adult readers. An analogical, lexically based parsing system for the reading and spelling of new (nonwords, as suggested by Marcel (1980) appears to be the best fit to these data.
Three patients with severe aphasia and right hemiplegia are described who could write to dictation with the right arm using a limb prosthesis though agraphic with the "intact" left hand. The phenomenon of "hemiplegic writing" is explained as an access to submerged or preprocessing levels in language and action structure, through the use of older proximal motor systems. This interpretation has implications for our understanding of language and brain function, as well as for approaches to the treatment of patients with severe language disorders.
A case of disconnection-type agraphia coupled with alexia was reported. The patient showed several asymmetrical manual capacities between the two hands, i.e., dissociated difficulty of Kanji (ideogram) writing between the two hands, left unilateral difficulty of Kana (phonogram) writing, right unilateral dyscopia of letters as well as geometrical figures, and right unilateral difficulty in drawing without a model. Anatomically, lesions involved most of the corpus callosum in its posterior portion including the splenium and the left medial occipital lobe. From these data, a possible linguistic capacity of the right hemisphere was suggested.
An experiment demonstrated a complete hemispheric processing reversal in 10 male, dysphonetic dyslexic children that occurred during a dichotic listening test of their verbal working memory. Requiring a written response to dichotic digits produced a right hemisphere/left ear superiority in the dysphonetic dyslexics whereas normal subjects and other dyslexics maintained a left hemisphere/right ear advantage. This reversal was unaffected by changes in task difficulty. A second experiment assessed the influence on producing the reversal of concurrent manual interference with left hemisphere verbal processing (responding orally vs. manually) and selective right hemisphere priming (Forward Writing vs. Backward Writing). The dysphonetic children reverted to a strong left hemisphere superiority when recalling the dichotic digits orally. Backward writing produced no ear advantage in either direction. The findings suggest that dysphonetic dyslexia may be related to (1) left hemisphere processing demands that exceed capacity, (2) easily activated right hemisphere processing strategies and (3) failure to coordinate linguistic processing interhemispherically. The results supported a novel hybrid conceptualization of dyslexia consisting of a synthesis of selective activation, and dual processor-limited capacity, theories.
An Italian patient with a pure dysgraphia who incorrectly spelled words and nonwords is described. The spelling errors made by the patient were not affected by lexical factors (e.g., frequency, form class) and were qualitatively the same for words and nonwords. The pattern of writing performance is discussed in relation to current models of writing and, specifically, in relation to the role of the Output Grapheme Buffer and Phoneme-Grapheme Conversion in writing.
The ability of an aphasic subject with agrammatism in both comprehension and production to transcribe quantities from Roman numerals to Arabic and the reverse was investigated. Systematic errors in the transcoding processes were observed that could not be accounted for by the peculiarities of the two ideographic coding systems or by difficulties with direct transcoding rules. The results are discussed in the framework of the current debate on preserved/impaired hierarchical syntactical knowledge of agrammatic subjects. The findings paralleled the results of previous studies on the transcoding skills of agrammatics from/to alphabetic numerals to/from digital forms. In the case of this particular patient, it is therefore tentatively concluded in favor of preserved syntactical knowledge.
Right-handers and left-handers with the inverted (IN) and noninverted (NI) writing posture were tested on a dichotic consonant-vowel listening task and on two motor tasks (hand strength and speed of tapping). The results failed to show the differences between IN and NI right-handers reported by S. M. Tapley and M. P. Bryden (1983, Neuropsychologia, 21, 129-138) and there were no significant handedness x writing posture x ear interactions. A significant interaction between dichotic listening performance and writing posture was found; NI right-handers and IN left-handers had more correct responses and fewer intrusions than IN right-handers and NI left-handers. Left-handers and right-handers were found to have a right ear advantage (REA) in the dichotic listening task but left-handers had relatively smaller left/right differences in all of the performance measures. Sample characteristics suggest that there are more IN male right-handers than IN female right-handers.
We report three cases of alexia with agraphia due to the left posterior inferior temporal lesions. In Case 1, the reading disability was more prominent in the use of Kana than in the use of Kanji, which is similar to previously reported cases of alexia with agraphia due to angular gyrus lesion. In Cases 2 and 3, by contrast, the reading disability was more prominent in the use of Kanji than in the use of Kana. In spontaneous writing and dictation, the disability was more pronounced in the use of Kanji compared with the use of Kana. In each of the three cases, the CT scan and positron emission tomography showed a localized lesion in the lower part of the left posterior temporal lobe. A typical form of an alexia with agraphia could be caused not only by the left angular lesion but also by the left posterior inferior temporal lesion. We discuss the neuropsychological analysis and pathogenetic mechanisms of alexia with agraphia due to the left posterior inferior temporal lesion in the comparison of alexia with agraphia caused by the left angular lesion.
When a disorder of single word writing is seen in conjunction with preserved oral spelling and intact written grapheme formation ("written spelling agraphia"), the deficit may be presumed to lie somewhere between letter choice and written motor output. Two potential deficits are considered: (1) visual letter codes are not activated properly and (2) the information contained within properly activated visual letter codes fails to reach intact graphic motor patterns. Two patients with written spelling agraphia were each given a series of tests aimed at distinguishing between the two possibilities. Results suggest that the written spelling agraphia seen in these two patients arises from different underlying deficits. The results are discussed in terms of the patients' CT scan lesion sites, which were markedly different.