Letter position dysgraphia

The article describes AE, a Hebrew-speaking individual with acquired dysgraphia, who makes mainly letter position errors in writing. His dysgraphia resulted from impairment in the graphemic buffer, but unlike previously studied patients, most of his errors related to the position of letters rather than to letter identity: 80% of his errors were letter position errors in writing, and only 7% of his errors were letter omissions, substitutions, and additions. Letter position errors were the main error type across tasks (writing to dictation and written naming), across output modalities (writing and typing), and across stimuli, e.g., migratable words (words in which letter migration forms another word), irregular words, and nonwords. Letter position errors occurred mainly in the middle letters of a word. AE's writing showed a significant length effect, and no lexicality, migratability, or frequency effects. His letter position deficit was manifested selectively in writing; he made no letter position errors in reading, demonstrating the dissociability of letter position encoding in reading and writing. These data support the existence of a letter order function in the graphemic buffer that is separate from the function responsible for activating letter identities.     

Developmental mirror-writing is paralleled by orientation recognition errors

The writing attempts of children often feature mirror-reversals of individual letters. These reversals are thought to arise from an adaptive tendency to mirror-generalize. However, it is unclear whether mirror-writing is driven by mirror-generalisation of the visual letter forms, or of the actions for writing them. We report two studies of the relationship between mirror-writing and the ability to recognize whether a visually presented letter is in the correct orientation, amongst primary and preschool children learning to read and write in English. Children who produced more mirror-writing also made more orientation recognition errors, for uppercase (Study 1, n?=?44) and lowercase letters (Study 2, n?=?98), and these relationships remained significant when controlling for age. In both studies, the letters more often reversed in writing were also more prone to orientation recognition errors. Moreover, the rates of mirror-writing of different uppercase letters were closely similar between the dominant and non-dominant hands (Study 1). We also note that, in the recognition tasks, children were more likely to accept reversed letters as correct, than to reject correctly oriented letters, consistent with a tendency to mirror-generalize the visual letter forms. In every aspect, these results support a major role for visual representations in developmental mirror-writing.     

Where do perseverations come from?

RB, a patient with probable Alzheimer's disease, makes continuous perseverations of single letters when writing (e.g. fruit-->fruuit), particularly on high frequency letters. An analysis of her errors reveals that her perseverations do not reflect letter substitutions or transpositions, nor do they suggest difficulty with geminates. No continuous perseverations were found in oral production, in graphic and simple motor tasks, and in oral spelling. RB's data do not support an attention deficit as the basis of her continuous perseverations. It is proposed that a deficit at the level of abstract letter representations is the source of RB's perseverations. The implications of this conclusion for accounts of perseveration and of spelling models are discussed.     

Dysgraphia for letters: a form of motor memory deficit?

A case of pure dysgraphia is presented in which the patient could accurately copy letters which she could not write. The patient did not show any evidence of significant reading or speech impairment or any buccofacial or limb apraxia. Both oral and "block spelling" performance were intact. The writing impairment, which was bilateral, appeared to consist of a memory difficulty for the motor movements associated with letters. The dysgraphia was shown to be specific to letters as the patient was able to transcribe certain numbers and patterns which were similar to letters in their visuospatial complexity. It is suggested that dysgraphia for letters may represent a specific type of motor memory deficit, dissociable from copying skills and the ability to draw letter-like forms.     

A cognitive-neuropsychological analysis of allograph errors from a patient with acquired dysgraphia

Abstract

This paper reports an investigation of the impaired writing of an acquired dysgraphic patient J.E.C. who made several case, substitution, omission, and addition errors when writing lower-case letters cursively, but whose upper-case writing was intact. The main finding was that damage to the lower-case letter production system results in errors that can be predicted from the spatial similarity of the lower-case form of the error to the lower-case form of the target. This was found with both within-case and cross-case letter substitutions. An additional observation was consistent cross-case errors occurred only with targets forming a single cluster of spatially similar lower-case letters (b, d, p, and q). It is concluded access to lower-case letters is constrained by spatial similarity of a target to other letters in allograph store, and this effect may explain letter errors made by dysgraphic patients.     

Dyscravia: Voicing substitution dysgraphia

We report a new type of dysgraphia, which we term dyscravia. The main error type in dyscravia is substitution of the target letter with a letter that differs only with respect to the voicing feature, such as writing “coat” for “goat”, and “vagd” for “fact”. Two Hebrew-speaking individuals with acquired dyscravia are reported, TG, a man aged 31, and BG, a woman aged 66. Both had surface dysgraphia in addition to their dyscravia. To describe dyscravia in detail, and to explore the rate and types of errors made in spelling, we administered tests of writing to dictation, written naming, and oral spelling. In writing to dictation, TG made voicing errors on 38% of the words, and BG made 17% voicing errors. Voicing errors also occurred in nonword writing (43% for TG, 56% for BG). The writing performance and the variables that influenced the participants’ spelling, as well as the results of the auditory discrimination and repetition tasks indicated that their dyscravia did not result from a deficit in auditory processing, the graphemic buffer, the phonological output lexicon, the phonological output buffer, or the allographic stage. The locus of the deficit is the phoneme-to-grapheme conversion, in a function specialized in the conversion of phonemes’ voicing feature into graphemes. Because these participants had surface dysgraphia and were forced to write via the sublexical route, the deficit in voicing was evident in their writing of both words and nonwords. We further examined whether the participants also evinced parallel errors in reading. TG had a selective voicing deficit in writing, and did not show any voicing errors in reading, whereas BG had voicing errors also in the reading of nonwords (i.e., she had dyslegzia in addition to dyscravia). The dissociation TG demonstrated indicated that the voicing feature conversion is separate for reading and writing, and can be impaired selectively in writing. BG's dyslegzia indicates that the grapheme-to-phoneme conversion also includes a function that is sensitive to phonological features such as voicing. Thus the main conclusion of this study is that a separate function of voicing feature conversion exists in the phoneme-to-grapheme conversion route, which may be selectively impaired without deficits in other functions of the conversion route, and without a parallel deficit in reading.     

Progressive dysgraphia in a case of posterior cortical atrophy

Dysgraphia (agraphia) is a common feature of posterior cortical atrophy (PCA). However, detailed analyses of these spelling and writing impairments are infrequently conducted. LM is a 59-year-old woman with dysgraphia associated with PCA. She presented with a two-year history of decline in her writing and dressmaking skills. A 3D T1-weighted MRI scan confirmed selective bi-parietal atrophy, with relative sparing of the hippocampi and other cortical regions. Analyses of LM's preserved and impaired spelling abilities indicated mild physical letter distortions and a significant spelling deficit characterised by letter substitutions, insertions, omissions, and transpositions that was systematically sensitive to word length while insensitive to real word versus nonword category, word frequency, regularity, imagery, grammatical class and ambiguity. Our findings suggest a primary graphemic buffer disorder underlies LM's spelling errors, possibly originating from disruption to the operation of a fronto-parietal network implicated in verbal working memory.     

Progressive Dysgraphia in a Case of Posterior Cortical Atrophy

Dysgraphia (agraphia) is a common feature of posterior cortical atrophy (PCA). However, detailed analyses of these spelling and writing impairments are infrequently conducted. LM is a 59-year-old woman with dysgraphia associated with PCA. She presented with a two-year history of decline in her writing and dressmaking skills. A 3D T 1 -weighted MRI scan confirmed selective bi-parietal atrophy, with relative sparing of the hippocampi and other cortical regions. Analyses of LM’s preserved and impaired spelling abilities indicated mild physical letter distortions and a significant spelling deficit characterised by letter substitutions, insertions, omissions, and transpositions that was systematically sensitive to word length while insensitive to real word versus nonword category, word frequency, regularity, imagery, grammatical class and ambiguity. Our findings suggest a primary graphemic buffer disorder underlies LM’s spelling errors, possibly originating from disruption to the operation of a fronto-parietal network implicated in verbal working memory.     

Dysgraphia in dementia

Abstract

This paper reviews the spelling and writing deficits associated with the major forms of dementia.In dementia of the Alzheimer's type (DAT), the finding of surface dysgraphia is typical, although not universal, and with disease progression non-phonologlcally plausible errors often increase; additional difficulties with handwriting are common. Surface dysgraphia is a predictable feature in semantic dementia, but In contrast to DAT, the mechanics of handwriting are usually preserved. In patients with posterior cortical atrophy [Including some (atypical) DAT patients], spatial dysgraphia is an early symptom. Spelling and writing disorders have been documented, although not thoroughly studied, in other forms of dementia (e.g. vascular, frontal, dementia with Lewy bodies, etc.). Research on dysgraphia in dementias associated with movement disorders (e.g. cortico-basal degeneration, progressive supranuclear palsy, Huntington's disease, etc.) has focused mainly on problems with writing, which is often poorly formed, but spelling impairments have also been observed. The precise characteristics and prevalence of spelling disorders in these diseases are, however, unknown as there has been little systematic study. Additional investigations, which assess both central (linguistic) and peripheral aspects of writing, and which include a longitudinal component, will help to elucidate the nature and progression of dysgraphia in different types of dementia.     

ADHD and dysgraphia: underlying mechanisms

Multiple complaints in the domain of writing are common among children with Attention Deficit Hyperactivity Disorder (ADHD). In this work we sought to characterize the writing disorder by studying dysgraphia in twenty 6th grade boys with ADHD and normal reading skills matched to 20 healthy boys who served as a comparison group. Dysgraphia, defined as deficits in spelling and handwriting, was assessed according to neuropsychological explanatory processes within 3 primary domains: linguistic processing, motor programming and motor kinematics. Children with ADHD made significantly more spelling errors, but showed a unique pattern introducing letter insertions, substitutions, transpositions and omissions. This error type, also known as graphemic buffer errors, can be explained by impaired attention aspects needed for motor planning. Kinematic manifestations of writing deficits were fast, inaccurate and an inefficient written product accompanied by higher levels of axial pen pressure. These results suggest that the spelling errors and writing deficits seen in children with ADHD and normal reading skills stem primarily from non-linguistic deficits, while linguistic factors play a secondary role. Recommendations for remediation include educational interventions, use of word processing and judicious use of psychostimulants.     

Progressive aphasia presenting with deep dyslexia and dysgraphia

Primary progressive aphasia is clinically heterogeneous. We report a patient, alias Don, with a novel form of progressive aphasia, characterised by deep dyslexia and dysgraphia and dissociated access to phonological and orthographic word forms. The hallmarks of deep dyslexia and dysgraphia were present early in the course and persisted over time. Writing was initially poorer than reading, but this reversed over time. There was a lack of concordance between reading and writing errors. Don benefited from a semantic mediation strategy to learn letter sounds, involving associating letters with a country name (e.g., A = Afghanistan). Remarkably, he continued to be able to generate those phonologically complex country names when no longer able to name or sound letters. Don’s performance is compatible with a traditional dual-route account of deep dyslexia and dysgraphia. The findings have potential practical implications for speech and language therapy in progressive aphasia. Moreover, they illustrate both the remarkable specificity yet clinical diversity in presentation of progressive aphasia.     

Task and stimulus demands influence letter-case-specific priming in the right cerebral hemisphere

A greater tendency to complete single-completion word stems (e.g. "BEY") to form previously read whole words (e.g. "BEYOND") was found when test stems were presented in the same letter case as their previously encoded words, compared with the different letter case, but only when stems were presented directly to the right hemisphere (i.e. in the left visual field) and not when they were presented directly to the left hemisphere (i.e. in the right visual field). This finding with single-completion stems was robust (i.e. observed for both lowercase and uppercase stems) when the initial encoding task was perceptually demanding, but it was test-case dependent (i.e. observed for uppercase but not lowercase stems) when the initial encoding task was not perceptually demanding. Results and theory help to explain why letter-case-specific priming in right-hemisphere test presentations is typically test-case dependent when priming is measured using perceptual identification at test, but is consistently robust when priming is measured using multiple-completion word stems (e.g."BEA") at test. Demands from both the stimuli and tasks affect the relative contributions of abstract and specific subsystems to the processing of visual forms.     

Mirror writing of digits and (capital) letters in the typically developing child

Typically developing 5- to 6-year-old children often reverse some digits (e.g., ? for 3) or single (capital) letters (e.g., Я for R) when they are required to write them under dictation. A theoretical approach to this phenomenon, based on an implicit right writing rule and that postulates an influence of the preceding writing, was tested in an experimental study of 300 children aged 5–6 years. The data support the implicit right writing rule and show the considerable influence of the preceding writing. For example, 73% of the children who correctly wrote the letter C mirror wrote an immediately following digit 3, whereas only 10% of the children who mirror wrote the letter C also mirror wrote an immediately following digit 3.     

Task and Stimulus Demands Influence Letter-case-Specific Priming in the Right Cerebral Hemisphere

A greater tendency to complete single-completion word stems (e.g. “BEY”) to form previously read whole words (e.g. “BEYOND”) was found when test stems were presented in the same letter case as their previously encoded words, compared with the different letter case, but only when stems were presented directly to the right hemisphere (i.e. in the left visual field) and not when they were presented directly to the left hemisphere (i.e. in the right visual field). This finding with single-completion stems was robust (i.e. observed for both lowercase and uppercase stems) when the initial encoding task was perceptually demanding, but it was test-case dependent (i.e. observed for uppercase but not lowercase stems) when the initial encoding task was not perceptually demanding. Results and theory help to explain why letter-case-specific priming in right-hemisphere test presentations is typically test-case dependent when priming is measured using perceptual identification at test, but is consistently robust when priming is measured using multiple-completion word stems (e.g.“BEA”) at test. Demands from both the stimuli and tasks affect the relative contributions of abstract and specific subsystems to the processing of visual forms.     

Letter selection and letter assembly in acquired dysgraphia.

OBJECTIVE: We explored the constituents of the graphemic buffer in a patient with acquired dysgraphia and tested the hypothesis that the graphemic buffer is composed of 2 dissociable components: letter selection and letter assembly. BACKGROUND: Research on dysgraphia has established the graphemic buffer as a component of the spelling mechanism, and the buffer is considered a short-term memory store that is critical for letter production. However, little is known about the components within the buffer. METHOD: We devised 2 spelling tasks that rely differentially on letter selection and letter assembly. In the selection task, our patient produced the letters that composed a target word, but she did not have to provide serial position information. In the assembly task, B.H. was given all the letters of a target word and was asked to spell the word by arranging the letters in the proper serial order. RESULTS: Compared to spelling to dictation, our patient did not benefit from being given letter identity information (ie, assembly task), but her performance improved significantly when position information was available (ie, selection task). CONCLUSIONS: Based on these data, and the comparison of her performance with another dysgraphic patient, we propose that the graphemic buffer engages in both letter selection and letter assembly.     

Disconnection agraphia in a case of multiple sclerosis: the isolation of letter movement plans from language

We report the case of a left-handed man (MCR), who presented with a peripheral agraphia as an early sign of multiple sclerosis. His left-handed writing was neologistic, whilst oral spelling, typing and spelling with the right hand were intact. Structural MRI scanning revealed a lesion of the body of the corpus callosum. Dichotic listening tests indicated that MCR displayed left hemisphere dominance for language. It is proposed that MCR represents a case of a disconnection syndrome in which right hemisphere systems that provide the basis for movement templates during left-handed writing are isolated from left hemisphere language systems. Analysis of left-handed writing indicated that peripheral movement control was highly structured with both individual letter frequency and sequential dependencies between letters represented within these motor control units. This case represents an opportunity to explore the mechanisms of movement control for writing and to examine the characteristics of isolated letter templates.     

Progressive Peripheral Agraphia

We describe RW, a patient who presented with writing difficulty that deteriorated over time. While her graphemes were typically legible, her writing was extremely slow, and her letters were written in an inconsistent and heterogeneous manner (e.g. each ‘a’ in the word ‘banana’ was produced in a different way). Her mental imagery of letters was impoverished, and she also produced allographic errors in her writing. She had some spelling errors as well, but many of these were due to omissions, perseverations, and motor operations. A positron emission tomography scan demonstrated superior parietal occipital and superior frontal defects that were more evident on the left than the right. Our observations are consistent with the hypothesis that RW has a deficit retrieving physical letter forms as manifested by her heterogeneous and slow production of letter forms. This disruption of grapheme retrieval is associated with interruption of a superior frontal-parietal system in the left hemisphere.     

Progressive peripheral agraphia

We describe RW, a patient who presented with writing difficulty that deteriorated over time. While her graphemes were typically legible, her writing was extremely slow, and her letters were written in an inconsistent and heterogeneous manner (e.g. each "a" in the word "banana" was produced in a different way). Her mental imagery of letters was impoverished, and she also produced allographic errors in her writing. She had some spelling errors as well, but many of these were due to omissions, perseverations, and motor operations. A positron emission tomography scan demonstrated superior parietal occipital and superior frontal defects that were more evident on the left than the right. Our observations are consistent with the hypothesis that RW has a deficit retrieving physical letter forms as manifested by her heterogeneous and slow production of letter forms. This disruption of grapheme retrieval is associated with interruption of a superior frontal-parietal system in the left hemisphere.