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.     

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.     

Limited retention of information in the graphemic buffer

This study examined a patient who mainly made letter deletion errors in spelling. It was hypothesized that his errors were due primarily to limited ability to retain information in the graphemic buffer, a structure that holds sequences of abstract letter identities for output. Consistent with this hypothesis, the patient's spelling accuracy declined on long words, but the number of letters he wrote per response was not related to word length. Moreover, by having him write words forward and backward, it was shown that his accuracy within a word depended on which part of the word he tried to output first. These results also ruled out alternative accounts of the patient's spelling deficit based on neglect or damage to lexical representations.     

Is a single graphemic buffer used in reading and spelling?

Background: The graphemic buffer was originally conceived as a component dedicated to the temporary storage of abstract orthographic representations prior to their format-specific expression in spelling (Caramazza, Miceli, Villa, & Romani, 1987). Since then, it has been argued that the graphemic buffer is also involved in reading (Caramazza, Capasso, & Miceli, 1996). Aims: The goal of this study was to test the hypothesis that a single graphemic buffer is used in reading and spelling. In addition, we examined the hypothesis that, under normal reading circumstances, words and pseudowords place different demands on the graphemic buffer because of differences in the degree to which they can be processed globally. Methods & Procedures: We performed detailed analyses of the reading and spelling performance of MC who presented with dyslexia (restricted to pseudowords) and dysgraphia following resection of a left parietal lobe tumour. Additionally, we compared the effect of presentation format (standard print, mirror reversed, and orally spelled stimuli) on word and pseudoword naming. Outcomes & Results: First, MC's spelling impairment showed all the characteristics of a graphemic buffer deficit. Second, MC's spelling of words and pseudowords as well as his reading of pseudowords were remarkably similar, both quantitatively and qualitatively (quasi-identical distribution of errors, length effect, and error position curves). Third, MC's reading of words (but not pseudowords) was disrupted under conditions that interfered with global (i.e., whole-word) processing. Conclusions: This study supports the claim that a single graphemic buffer is used in reading and spelling. It also suggests that reading nonwords places greater demands on the graphemic buffer than reading words.     

Dysgraphia in primary progressive aphasia: Characterisation of impairments and therapy options

Background: Spelling impairment is common in primary progressive aphasia (PPA). Although behavioural interventions tend to focus on spoken language, remediation of written language may be desirable, either because an individual’s regular use of writing makes it a priority or because writing is needed for communication in cases where it is better preserved than spoken language.

Aims: This paper has three aims: (1) to provide an up-to-date survey of spelling and handwriting impairments in each variant of PPA, (2) to provide guidance on characterisation of dysgraphia and identification of loci of impairment, and (3) to outline possible interventions. Because the number of studies which have specifically evaluated therapy for dysgraphia in PPA is small, this paper also reviews relevant studies of therapy in non-progressive dysgraphia.

Main Contribution: Review of the literature indicated that the most common pattern of spelling impairment in the semantic variant of PPA is surface dysgraphia (impairment in lexical spelling). The profile is more variable in the non-fluent and logopenic variants of PPA, but most commonly there is impairment in lexical spelling and in phoneme-to-grapheme conversion. Review of the literature on therapy for dysgraphia indicated that four main types of therapy have been evaluated and shown to improve spelling performance: (1) training of spelling of specific target words (used to ameliorate lexical and graphemic buffer impairments), (2) training of sound-to-spelling correspondence rules (used to treat impairment in assembled spelling), (3) training in segmentation of stimulus words into smaller chunks (to make them manageable for a damaged graphemic buffer, or as a first stage in applying sound-to-spelling correspondence rules), and (4) learning to identify and self-correct errors (used in treatment of graphemic buffer disorder).

Conclusions: It is likely that spelling impairment in PPA would be responsive to treatment, although this has only been demonstrated in the logopenic variant. Reported improvements following therapy for anomia demonstrate that relearning is possible in PPA, despite the progressive nature of the condition. This gives reason for optimism regarding a positive response to therapy for dysgraphia in all variants of PPA.     

Using orthographic neighbours to treat a case of graphemic buffer disorder

Background: The characteristics of graphemic buffer disorder have been described by Miceli, Silveri, and Caramazza (1985) and Caramazza and Miceli (1990) and include a length effect in spelling words and nonwords, in both written and oral format. Error patterns typically consist of omissions, substitutions, additions, and movement errors. Recently, lexical effects on spelling accuracy in many buffer cases have been shown (Sage & Ellis, 2004) and, in patient BH in particular, these included an influence of orthographic neighbourhood size (the number of words that can be generated by changing one letter in the target word; Coltheart, Davelaar, Jonassen, & Besner, 1977). Aims: This paper aims to show that orthographic neighbours used in a therapy programme can bring about improvements in the spelling of targets that have not directly received therapy. Methods & procedures: This was a single case treatment study of BH, who showed classic features of graphemic buffer disorder in her spelling. Two priming studies contrasting no prime, control primes, and orthographic neighbour primes (both word and nonword) established that positive effects on spelling accuracy and error pattern could be achieved. The use of orthographic neighbours was then extended into a therapy programme. Three word sets contrasted direct therapy to the words themselves (Set1), no therapy at all (Set 2), and therapy to neighbours of the words in a set (Set 3). An errorless learning paradigm was used throughout the therapy programme. Outcome & results: Improvement was made both to the treated words in Set 1 and to the words in Set 3, even though these words had received no direct therapy. There was no change in accuracy in Set 2, the control set that had received no therapy. The paper also explores changes in error patterns due to therapy, showing that error patterns changed following therapy. Conclusions: The priming studies showed that changes in accuracy could be achieved when orthographic neighbours were used. Following on from this, a therapy programme based on neighbours was effective in assisting the graphemic buffer. Specifically, the interaction between lexicon and buffer was used therapeutically to improve not only the spelling of words that had received direct treatment but also to a word set that did not directly receive treatment. These changes were brought about using an errorless learning paradigm.     

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.     

Do activated letters influence lexical selection in written word production?

Background: Written communication has become increasingly important since the advent of digital media such as emailing and texting. Research into the nature of interaction between the cognitive processes underlying production have focused on spoken language. Less is known about the processes underlying written word production.

Aims: We investigated the presence of feedback from letter activation to lexical selection in written word production. The presence of feedback would lead to greater-than-chance orthographic overlap between targets and semantically-related word errors in acquired dysgraphia, as the semantic neighbours of a target word sharing orthographic structure would receive extra support during lexical selection.

Methods & Procedures: The orthographic overlap of written semantically-related word errors from an individual with acquired dysgraphia was compared to chance distributions of overlap generated using a word association database. We used a Monte Carlo procedure to select random “pseudo-errors” from the top semantic associates for each target word. 10,000 hypothetical datasets were generated for two distinct hypotheses regarding the likelihood of selecting particular semantically-related word errors.

Outcomes & Results: The orthographic overlap between target words and semantically-related word errors for the individual with dysgraphia was greater than any of the hypothetical datasets, indicating that the target-error pairs shared more orthographic structure than expected by chance (p < .0001).

Conclusions: We obtained evidence that feedback from letter activation influenced lexical selection in a case of impairment. The presence of feedback from letter activation to lexical selection may be useful in developing strategies leading to improved language production in individuals with dysgraphia and aphasia.     

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.     

Patterns of breakdown in spelling in primary progressive aphasia

Introduction

The objective of this study is to determine which cognitive processes underlying spelling are most affected in the three variants of primary progressive aphasia (PPA): Logopenic variant primary progressive aphasia (lvPPA), Semantic variant primary progressive aphasia (svPPA), and Nonfluent variant primary progressive aphasia (nfvPPA).

Methods

23 PPA patients were administered The Johns Hopkins Dysgraphia Battery to assess spelling. Subtests evaluate for effects of word frequency, concreteness, word length, grammatical word class, lexicality (words vs pseudowords), and “regularity” by controlling for the other variables. Significant effects of each variable were identified with chi square tests. Responses on all spelling to dictation tests were scored by error type. 16 of the 23 subjects also had a high resolution MRI brain scan to identify areas of atrophy.

Results

We identified 4 patterns of spelling that could be explained by damage to one or more cognitive processes underlying spelling. Nine patients (3 unclassifiable, 4 with lvPPA, 2 with svPPA) had dysgraphia explicable by impaired access to lexical representations, with reliance on sublexical phonology-to-orthography conversion (POC). Two patients (with nfvPPA) showed dysgraphia explicable by impaired access to lexical representations and complete disruption of sublexical POC. Seven patients (4 with lvPPA, 1 with svPPA, 2 unclassifiable) showed dysgraphia explicable by impaired access to lexical-semantic representations and/or lexical representations with partially spared sublexical POC mechanisms. Five patients (1 with nfvPPA, 2 with svPPA, 1 with lvPPA, and 1 unclassifiable) showed dysgraphia explicable by impairment of the graphemic buffer.

Conclusions

Any cognitive process underlying spelling can be affected in PPA. Predominance of phonologically plausible errors, more accurate spelling of regular words than irregular words, and more accurate spelling of pseudowords than words (indicating spared POC mechanisms) may indicate a low probability of progression to nfvPPA.     

Rehabilitation of spelling in a participant with a graphemic buffer impairment: The role of orthographic neighbourhood in remediating the serial position effect

Graphemic Output Buffer (GOB) disorder is defined as difficulty with the serial output of a sequence of letters in the output stage of the spelling process. In their rehabilitation study with a GOB patient, Sage and Ellis (2006 Sage, K. and Ellis, A. W. 2006. Using orthographic neighbours to treat a case of graphemic buffer disorder. Aphasiology, 20: 851–870. (doi:10.1080/02687030600738945)[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) found that improvement on treated words generalised to untreated words from the same orthographic neighbourhoods as treated items, but not to other unrelated words. GOB patients frequently show a bow-shaped accuracy curve across letter positions, where letters at the middle positions are most error-prone. It may be that consistent letters at these middle letter positions across neighbourhoods modulate this effect. Spelling was treated using an Anagram and Copy Treatment (ACT) and generalisation to three untreated sets was examined: (1) neighbours of treated words with shared middle letters (e.g., clock–block), (2) neighbours with different medial position letters (e.g., clock–click), and (3) unrelated words (e.g., clock–puppy). Improvement was found for untreated neighbours with shared middle letters. There was no effect of training on the unrelated word set, and a negative impact on untreated neighbours with changed middle letters after the treatment. We attribute these results to top-down support from learned lexical representations, which facilitate spelling of untreated neighbours with shared middle letters but impede neighbours with changed middle letters. This latter result is attributed to interference from neighbours in the trained set strengthening competing letter representations at middle positions.     

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.     

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.     

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.