Pure agraphia and Gerstmann's syndrome as a visuospatial-language dissociation: an experimental case study

A right-handed man suffered a left parieto-occipital cerebral infarction, causing agraphia with Gerstmann's syndrome but without major aphasia, alexia, or apraxia. Oral spelling was superior to written spelling. Experiments were performed involving (1) analysis of errors in writing, (2) tasks of visual imagery, and (3) identifying letters drawn without leaving a visual trace. The results suggest that the agraphia and Gerstmann's syndrome are due to a dissociation of language skills and visuospatial skills caused by a dominant parieto-occipital lesion.     

Agraphia selective for written spelling : An experimental case study

A 56-year-old right-handed man suffered left posterior parieto-temporal ischemia leading to mild aphasia, Gerstmann syndrome, and a novel variant of agraphia. This variant compromised his spelling by writing and manual sorting of letters more than his oral spelling. The dissociation was experimentally documented. It principally involved the intrusion of extraneous letters, independent of input modality. It did not generalized to numbers or an arbitrary code. Postoperatively the disability disappeared. It was concluded that the programs which translate letter choice into visual terms for purposes of written (as distinct from oral) spelling either originate or are transmitted in a distinct cerebral location. This location, which may be the left posterior parasagittal parietal area, can be selectively impaired by a focal lesion.     

Progressive agraphia can be a harbinger of degenerative dementia

By investigating three patients with progressive agraphia, we explored the possibility that this entity is an early sign of degenerative dementia. Initially, these patients complained primarily of difficulties writing Kanji (Japanese morphograms) while other language and cognitive impairments were relatively milder. Impairments in writing Kana (Japanese syllabograms), verbal language, executive function, visuo- and visuospatial cognition and memory were identified by neuropsychological testing. The agraphia was compatible with a peripheral type, based on deficits at the interface between the central letter selection and the graphemic motor execution (Patient 1) or at the stage of central letter selection as well (Patients 2 and 3). Agraphia was generally more prominent, although not exclusive, for Kanji probably because of later acquisition and larger total number of Kanji letters leading to lower frequency of use and familiarity per letter. Concurrent or subsequent emergence of non-fluent aphasia, ideomotor apraxia, executive dysfunction and asymmetric akinetic-rigid syndrome in two patients suggested degenerative processes involving the parietal-occipital-temporal regions, basal ganglia and striato-frontal projections. We propose that progressive agraphia may be one of the early symptoms of degenerative dementia such as corticobasal degeneration.     

Deep agraphia

A case of agraphia is documented which resembles in every respect the pattern of results obtained in deep dyslexia. Pronounceable pseudowords could not be written to dictation while concrete nouns were more accurately transcribed than abstract nouns. Verbs and functions words were written very poorly and oral spelling was impaired. In addition, semantic paragraphias were present. In contrast to the deficit observed in writing, no such impairment was found for reading. It is concluded that writing can occur without phoneme-grapheme conversion and that codes generated for reading are functionally distinct from codes generated for writing.     

Phonological codes and functional spelling units: Reality and implications

The grapheme-to-phoneme correspondence procedure for generating nonlexical phonological codes comprises two stages. The first, a parsing procedure, divides a letter string into functional spelling units (FSUs), each unit corresponding to a single phoneme. The second stage assigns the appropriate phoneme to the spelling units according to predictable or regular spelling-tosound patterns. In a lexical decision task, it was found that disrupting the spelling units, by alternating the case of letters within the units (e.g., ChuRCH) caused the pseudohomophone effect to be abolished. In contrast, disrupting the visual appearance of the letter strings but leaving the FSUs intact (e.g., CHurCH) allowed the pseudohomophone effect to emerge. The results are considered in the light of the recent “activation and synthesis” model proposed by Glushko (1979).     

Multiple levels of letter representation in written spelling: evidence from a single case of dysgraphia with multiple deficits

In this paper, we report a detailed analysis of the impaired performance of a dysgraphic individual, AD, who produced similar rates of letter-level errors in written spelling, oral spelling, and typing. We found that the distribution of various letter error types displayed a distinct pattern in written spelling on the one hand and in oral spelling and typing on the other. In particular, noncontextual letter substitution errors (i.e., errors in which the erroneous letter that replaces the target letter does not occur elsewhere within the word) were virtually absent in oral spelling and typing and mainly found in written spelling. In contrast, letter deletion errors and multiple-letter errors were typically found in oral spelling and very exceptional in written spelling. Only contextual letter substitution errors (i.e., errors in which the erroneous letter that replaces the target letter is identical to a letter occurring earlier or later in the word) were found in similar proportions in the three tasks. We argue that these contrasting patterns of letter error distribution result from damage to two distinct levels of letter representation and processing within the spelling system, namely, the amodal graphemic representation held in the graphemic buffer and the letter form representation computed by subsequent writing-specific processes. Then, we examined the relationship between error and target in the letter substitution errors produced in written and oral spelling and found evidence that distinct types of letter representation are processed at each of the hypothetized levels of damage: symbolic letter representation at the graphemic level and representation of the component graphic strokes at the letter form processing level.     

Written spelling deficit of Broca''s aphasics

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.     

Preserved orthographic length and transitional probabilities in written spelling in a case of acquired dysgraphia

We present the performance of a patient with acquired dysgraphia, DS, who has intact oral spelling (100% correct) but severely impaired written spelling (7% correct). Her errors consisted entirely of well-formed letter substitutions. This striking dissociation is further characterized by consistent preservation of orthographic, as opposed to phonological, length in her written output. This pattern of performance indicates that DS has intact graphemic representations, and that her errors are due to a deficit in letter shape assignment. We further interpret the occurrence of a small percentage of lexical errors in her written responses and a significant effect of letter frequencies and transitional probabilities on the pattern of letter substitutions as the result of a repair mechanism that locally constrains DS' written output.     

The graphemic buffer and attentional mechanisms

Two patients with acquired dysgraphia were reported. The patients' performance in various written and oral spelling tasks converge in support of the hypothesis that they have selective damage, within the spelling system, to the Graphemic Buffer. Although the patients present with comparable patterns of error types, they differ in the distribution of errors as a function of letter position in words. The patients' patterns of errors are compared to previously reported patterns of spelling errors in dysgraphic patients and are discussed in terms of hypothesized mechanisms that operate on the representations that are stored in the Graphemic Buffer.     

Developmental phonological and lexical agraphia in adults

Many cases of agraphia from acquired cerebral lesions may be divided into two groups, phonological and lexical, suggesting two dissociable spelling systems. Studies of developmental agraphia have described some children who have spelling patterns similar to acquired phonological or lexical agraphia. This study analyzed spelling results from 22 adolescent and adult subjects with developmental agraphia (DA) and compared them to those from control subjects and subjects with acquired agraphia (AA). On the basis of spelling ability, subjects with DA could be divided into two groups. Analysis of the profile of spelling abilities indicated that the two groups of subjects with DA were almost indistinguishable from the two groups of subjects with AA, phonological and lexical. This supports the contention that DA in adults may be divided into phonological and lexical groups and further supports the two-system hypothesis for linguistic agraphia.     

Comparison between Oral and Written Spelling in Alzheimer's Disease

Written and oral spelling were compared in 33 patients with Alzheimer's disease (AD) and 25 control subjects. AD patients had poorer spelling results which were influenced by orthographic difficulty and word frequency, but not by grammatical word class. Lexical spelling was also more deteriorated than phonological spelling. Moreover, oral spelling was more impaired than written spelling in AD patients, whereas no difference was present between oral and written spelling of controls. Analysis of spelling errors showed that, for controls, errors were predominantly phonologically accurate in both spelling tasks. Significantly, AD patients produced more phonologically accurate than inaccurate errors in written spelling, whereas these errors did not differ in oral spelling. In contrast to controls who produced more constant than variable responses in oral and written spelling, AD patients made more variable responses (words correctly spelled in one task but incorrectly in the other) and they showed many instances of variable errors (different misspellings from one spelling task to the other). Two stepwise regression procedures showed that written misspellings were specifically correlated with language impairment, whereas oral spelling errors were correlated with attentional and language disorders. These results suggest that AD increases the attentional demands of oral spelling process as compared to written spelling. This dissociation argues, either for a unique Graphemic Buffer in which oral spelling requires more attentional resources than written spelling or for the hypothesis of separate buffers for oral and written spelling.     

Multiple component agraphia in a patient with atypical cerebral dominance: an error analysis

A 52-year-old man with atypical cerebral dominance (left-handed for writing but mixed handedness for other tasks) suffered an extensive right hemisphere stroke, resulting in a combination of deficits that has not been previously reported. There were profound visual constructive and visual perceptual disturbances and a spatial agraphia, which were consistent with a nondominant hemisphere lesion. There was also a severe apraxic agraphia, which is typically associated with a dominant hemisphere lesion, but no other signs of dominant hemisphere dysfunction such as linguistic disturbance or limb-motor apraxia were present. This case serves to highlight the functional and anatomical relationship between handwriting and other forms of praxis; the various sources of error in letter formation; the need to be specific in labeling and describing agraphias ; and the role of a detailed analysis of writing errors in delineating the neuropsychological processes involved in handwriting.     

Varieties of alexia from fusiform, posterior inferior temporal and posterior occipital gyrus lesions

Reading impairments of three alexia patients, two pure alexia and one alexia with agraphia, due to different lesions were examined quantitatively, using Kanji (Japanese morphogram) words, Kana (Japanese phonetic writing) words and Kana nonwords. Kana nonword reading was impaired in all three patients, suggesting that widespread areas in the affected occipital and occipitotemporal cortices were recruited in reading Kana characters (corresponding to European syllables). In addition, the findings in patient 1 (pure alexia for Kanji and Kana from a fusiform and lateral occipital gyri lesion) and patient 2 (pure alexia for Kana from a posterior occipital gyri lesion) suggested that pure alexia could be divided into two types, i.e. ventromedial type in which whole-word reading, together with letter identification, is primarily impaired because of a disconnection of word-form images from early visual analysis, and posterior type in which letter identification is cardinally impaired. Another type of alexia, alexia with agraphia for Kanji from a posterior inferior temporal cortex lesion (patient 3), results from deficient whole-word images of words per se, and thus should be designated "orthographic alexia with agraphia". To account for these impairments, a weighted dual-route hypothesis for reading is suggested.     

Cerebellar-induced apraxic agraphia: a review and three new cases

Apraxic agraphia is a writing disorder due to a loss or lack of access to motor engrams that program the movements necessary to produce letters. Clinical and functional neuroimaging studies have demonstrated that the neural network responsible for writing includes the superior parietal region and the dorsolateral and medial premotor cortex. Recent studies of two cases with atypical lesion localisations in the left thalamus and the right cerebellum support the hypothesis that the written language network is larger than previously assumed. The aim of this study is twofold: (1) to provide a survey of cases of apraxic agraphia published between 1973 and June 2010, and (2) to provide further evidence for a role of the cerebellum in writing via three additional cases who presented with apraxic agraphia after ischemic damage in the cerebellum. Functional neuroimaging studies by means of brain perfusion SPECT showed perfusional deficits in the anatomoclinically suspected supratentorial areas, subserving language dynamics, syntax, naming, writing and executive functioning.     

Visual memory in a spelling matching task: comparison of good and poor spellers

The role of visual memory in learning to spell words was investigated through a matching task on which one nonsense word was presented, then a second word identical in spelling or differing in one letter was presented. Ten pairs of 9th and 10th-grade students, matched for intelligence and sex but of different spelling ability, were asked to indicate whether word pairs were spelled the same or differently. The two words of a pair were either the same or different in print size or letter case. Significant effects were obtained for spelling ability, print size (same or different), and letter case (same or different), and the interaction of size X case, providing evidence for the use of visual memory by both good and poor spellers in learning to spell words. Good spellers were equally able to identify matched and mismatched pairs, while poor spellers showed greater difficulty in identifying mismatches than matches, supporting Frith's (1980) "partial cues" explanation of poor spelling performance.     

Long-term repetition priming in spoken and written word production: evidence for a contribution of phonology to handwriting

Although it is relatively well established that access to orthographic codes in production tasks is possible via an autonomous link between meaning and spelling (e.g., Rapp, Benzing, & Caramazza, 1997), the relative contribution of phonology to orthographic access remains unclear. Two experiments demonstrated persistent repetition priming in spoken and written single-word responses, respectively. Two further experiments showed priming from spoken to written responses and vice versa, which is interpreted as reflecting a role of phonology in constraining orthographic access. A final experiment showed priming from spoken onto written responses even when participants engaged in articulatory suppression during writing. Overall, the results support the view that access to orthography codes is accomplished via both the autonomous link between meaning and spelling and an indirect route via phonology.     

Alexia and agraphia with spared spelling and letter recognition abilities

A patient with alexia and agraphia had intact spelling and comprehension of spelled words and used a letter-naming strategy to read and write. We propose that there is a graphemic area important for distinguishing graphemic features and for programming movements used in writing. In this patient this area was not functioning or did not have access to the area of visual word imagés. Therefore, he used an ideographic letter-naming strategy to verbally circumvent his disability and gain access to the area of visual word images.     

Perseverative Writing Errors in a Patient with Alzheimer's Disease

This study reports the writing performance of a dysgraphic patient with Alzheimer's disease and moderate dementia who frequently perseverated on strokes and letters. Letter formation errors were also frequently produced. Oral spelling was superior to written spelling. The habitual style of writing (cursive writing) was significantly more prone to perseverations than writing in uppercase letters, a form of writing less frequently used by the patient. Central (linguistic) spelling processes were relatively preserved. The pattern of preserved and impaired functions is consistent with impairment of the peripheral mechanism that generates the graphic motor patterns code. We suggest that damage to the peripheral orthographic mechanism may cause deficits in some patients with Alzheimer's disease.     

A different form of agraphia: Syntactic writing errors in patients with motor speech and movement disorders

Three patients are described who displayed syntactic writing errors in combination with a motor speech disturbance and impaired motor limb function. Two of the patients had bulbar amyotrophic lateral sclerosis (ALS). Agraphia appeared when verbal communication was no longer possible. Autopsy in one patient disclosed only lesions consistent with ALS. The third patient had palilalia and chorea and, although not aphasic, his written language showed persistent syntactic errors. We hypothesize that the agraphia in these patients occurred because of the combination of disordered feedback from the motor speech apparatus and limbs.