Spelling and dysgraphia

Dysgraphia and Memory: Insights into the Cognitive Mechanisms, Neural Correlates, and Intervention Strategies

Studies regarding dysgraphia, an impairment in writing, have been receiving more attention in recent research. Most studies have broadly discussed the multiple cognitive mechanisms involved in writing and its disruption leading to dysgraphia. However, little attention has been paid to the involvement of different memory systems integral to writing and its disruption in individuals with dysgraphia. Orthographic long-term memory and orthographic working memory are the two memory systems predominantly involved in the production of written expressions, and the subsequent interruption of these memory systems often leads to varied deficit profiles of dysgraphia. These disruptions have resulted from damage in the brain caused by neural injuries, neurological disorders, or epigenetic factors. The existing studies did not probe into the nuances of the disruptions of these two memory systems in dysgraphia and associated neural pathways. In order to fill this gap, the review attempts to provide a comprehensive account of dysgraphia and its association with orthographic long-term memory and orthographic working memory by comparing and contrasting their workings and patterns of disruption in the deficit profiles of dysgraphia by probing into the underlying neural correlates. Such a detailed account brings insights into pertinent intervention strategies for improving memory systems and dysgraphia. It also helps identify the limitations of the existing intervention methods like CART, ACT, or Spell-Study-Spell, leading to the proposal of improvised neuro-targeted interventions for dysgraphia.

Do letters matter? The influence of spelling on acoustic duration

The present article describes a modified and extended replication of a corpus study by Brewer (2008. Phonetic reflexes of orthographic characteristics in lexical representation. Tucson, AZ: University of Arizona PhD thesis) which reports differences in the acoustic duration of homophonous but heterographic sounds. The original findings point to a quantity effect of spelling on acoustic duration, i.e., the more letters are used to spell a sound, the longer the sound's duration. Such a finding would have extensive theoretical implications and necessitate more research on how exactly spelling would come to influence speech production. However, the effects found by Brewer (2008) did not consistently reach statistical significance and the analysis did not include many of the covariates which are known by now to influence segment duration, rendering the robustness of the results at least questionable. Employing a more nuanced operationalization of graphemic units and a more advanced statistical analysis, the current replication fails to find the reported effect of letter quantity. Instead, we find an effect of graphemic complexity. Speakers realize consonants that do not have a visible graphemic correlate with shorter durations: the /s/ in tux is shorter that the /s/ in fuss. The effect presumably resembles orthographic visibility effects found in perception. In addition, our results highlight the need for a more rigorous approach to replicability in linguistics.

The Modularity of Dysgraphia

Research regarding dysgraphia, an impairment in writing, is attaining more attention in recent times. The existing studies on dysgraphia draw insights from cognitive, behavioural, neurological, and genetic fields of knowledge. However, these multiple studies on dysgraphia fail to illustrate how these cognitive, behavioural, neurological, and genetic systems interact and intersect in dysgraphia. Therefore, the studies could not offer a comprehensive understanding of dysgraphia. In order to fill this gap, the review attempts to study dysgraphia using the notion of modularity by accommodating insights from cognitive, behavioural, neurological, and genetic aspects of dysgraphia. Such a profound understanding could facilitate an early diagnosis and holistic intervention towards dysgraphia.

Word Reading and Spelling Processing and Acquired Dyslexia post Unilateral Stroke

This study investigates the performance of adults with cerebrovascular lesion in the right hemisphere (RHL) or left hemisphere (LHL) in word reading (TLPP) and spelling (TEPP) tasks based on the dual-route models. A total of 85 adults were assessed, divided into three groups: 10 with RHL, 15 with LHL, and 60 neurologically healthy ones. The performance of the three groups was compared in terms of the characteristics of the words (regularity, frequency, and length) and pseudowords (length), error types, and psycholinguistic effects. A cluster analysis was performed to investigate the profiles of the reading. The LHL group showed lower scores in reading and spelling tasks of words and pseudowords, as well as a higher frequency of errors. Four LHL cases were found to have an acquired dyslexia profile. This study highlights that the tasks developed in Brazil are in accordance with theoretical models of written language, and the results point to the heterogeneous performance of the cases with acquired dyslexia.

Two types of developmental surface dysgraphia: to bee but not to bea

We report on two types of developmental surface dysgraphia. One type, exhibited by 8 participants, is orthographic lexicon surface dysgraphia, which involves an impairment in the orthographic output lexicon, leading to nonword phonologically-plausible misspellings. The other type, shown by 3 participants, is disconnection surface dysgraphia. In this type, the orthographic output lexicon is disconnected from the semantic system and from the phonological input lexicon, but still contributes to spelling via support to the orthographic output buffer, resulting in mainly lexical phonologically-plausible misspellings (writing be as "bee" but not "bea").The specific localization of the impairment in spelling, in the lexicon or in its connections, allowed us to examine the question of one or two orthographic lexicons; four participants who had a deficit in the orthographic output lexicon itself in writing had intact orthographic-input-lexicon in reading. They made surface errors in writing but not in reading the same words, supporting separate input and output orthographic lexicons.

Speech and Language Therapy for Acquired Central Dysgraphia in Neurological Patients: A Systematic Review to Describe and Identify Trainings for Clinical Practice

PURPOSE

Acquired central dysgraphia is a heterogeneous neurological disorder that usually co-occurs with other language disorders. Written language training is relevant to improve everyday skills and as a compensatory strategy to support limited oral communication. A systematic evaluation of existing writing treatments is thus needed.

METHOD

We performed a systematic review of speech and language therapies for acquired dysgraphia in studies of neurological diseases (PROSPERO: CRD42018084221), following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) checklist with a search on several databases for articles written in English and published until August 31, 2021. Only methodological well-designed studies were included. Further assessment of methodological quality was conducted by means of a modified version of the Downs and Black checklist.

RESULTS

Eleven studies of 43 patients in total were included. For each study, we collected data on type of population, type of impairment, experimental design, type of treatment, and measured outcomes. The studies had a medium level of assessed methodological quality. An informative description of treatments and linkages to deficits is reported.

CONCLUSIONS

Although there is a need for further experimental evidence, most treatments showed good applicability and improvement of written skills in patients with dysgraphia. Lexical treatments appear to be more frequently adopted and more flexible in improving dysgraphia and communication, especially when a multimodal approach is used. Finally, the reported description of treatment modalities for dysgraphia in relation to patients' deficits may be important for providing tailored therapies in clinical management.

Properties of graphic motor plans in the writing system

The present study explores the extent to which properties of abstract graphemic representations are maintained at the post-graphemic level of graphic motor plans, where the sequences of writing strokes for producing the letters in a word are represented. On the basis of results from a stroke patient (NGN) who has a deficit affecting the activation of graphic motor plans, we explore the post-graphemic representation of 1) consonant/vowel status of letters; 2) geminate (double) letters, such as the BB in RABBIT; and 3) digraphs, such as the SH in SHIP. Through analyses of NGN's letter substitution errors, we conclude that 1) consonant-vowel status is not represented at the level of graphic motor plans; 2) geminates have special representations at the motor-plan level, as at the graphemic level; and 3) digraphs are represented by two separate single-letter graphic motor plans, and not by unitary digraph motor plans.

The Orthographic Ambiguity of the Arabic Graphic System: Evidence from a Case of Central Agraphia Affecting the Two Routes of Spelling

The Arabic writing system includes ambiguities that create difficulties in spelling. These ambiguities relate mainly to the long vowels, some phoneme-grapheme conversions, lexical particularities, and the connectivity of letters. In this article, the first to specifically explore acquired spelling impairments in an Arabic-speaking individual, we report the case of CHS, who presented with agraphia following a stroke. Initial testing indicated substantial impairment of CHS’s spelling abilities in the form of mixed agraphia. The experimental study was specifically designed to explore the influence of the orthographic ambiguity of the Arabic graphemic system on CHS’s spelling performance. The results revealed that CHS had substantial difficulties with orthographic ambiguity and tended to omit ambiguous graphemes. Some of the errors she produced suggested reliance on the sublexical route of spelling, while others rather reflected the adoption of the lexical-semantic route. These findings from a case involving a non-Western, non-Indo-European language contribute to discussions of theoretical models of spelling. They show that CHS’s pattern of impairment is consistent with the summation hypothesis, according to which the lexical-semantic and the sublexical routes interactively contribute to spelling.

Contribution of the Cognitive Approach to Language Assessment to the Differential Diagnosis of Primary Progressive Aphasia

Diagnosis of primary progressive aphasia (PPA) is essentially based on the identification of progressive impairment of language abilities while other cognitive functions are preserved. The three variants of PPA are characterized by core and supportive clinical features related to the presence or absence of language impairment in different linguistic domains. In this article, we review the cognitive neuropsychological approach to the assessment of PPA and its contribution to the differential diagnosis of the three variants. The main advantage of this assessment approach is that it goes beyond the mere description and classification of clinical syndromes and identifies impaired and preserved cognitive and linguistic components and processes. The article is structured according to the main language domains: spoken production, language comprehension, and written language. Each section includes a brief description of the cognitive processes involved in the assessment tasks, followed by a discussion of typical characteristics for each PPA variant and common pitfalls in the interpretation of the results. In addition, the clinical benefit of the cognitive neuropsychological approach for the behavioral management of PPA is briefly sketched out in the conclusion.

Serial position effects in graphemic buffer impairment: An insight into components of orthographic working memory

This study investigated the nature of graphemic buffer functioning and impairment, through analysis of the spelling impairment shown by GEC, a man with acquired dysgraphia and clear characteristics of graphemic buffer impairment. We discuss GEC's error patterns in relation to different processes of orthographic working memory. This is the first study to show the contribution of these processes in one individual through performance on different spelling tasks. GEC's spelling errors in writing to dictation showed a linear serial position effect, including deletions of final letters. These "fragment errors" can be explained as the result of information rapidly decaying from the buffer (reduced temporal stability). However, in tasks that reduced working memory demands, GEC showed a different error distribution that may indicate impairment to a different buffer process (reduced representational distinctiveness). We argue that different error patterns can be a reflection of subcomponents of orthographic working memory that can be impaired separately.

Primary motor cortex and phonological recoding: A TMS-EMG study

Since the 1960s, evidence from healthy participants and brain-damaged patients, neuroimaging and non-invasive brain stimulation studies has specified the neurofunctional architecture of the short-term memory (STM) system, supporting the temporary retention of a limited amount of verbal material. Auditory-verbal, later termed Phonological (Ph) STM or Phonological Loop, comprises two sub-components: i) the main storage system, the Phonological Short-Term Store (PhSTS), to which auditory verbal stimuli have direct access and where phonologically coded information is retained for a few seconds; ii) a Rehearsal Process (REH), which actively maintains the trace held in the PhSTS, preventing its decay and conveys visual verbal material to the PhSTS, after the process of Phonological Recoding (PhREC, or Grapheme-to-Phoneme Conversion) has taken place. PhREC converts visuo-verbal graphemic representations into phonological ones. The neural correlates of PhSTM include two discrete regions in the left hemisphere: the temporo-parietal junction (PhSTS) and the inferior frontal gyrus in the premotor cortex (REH). The neural basis of PhREC has been much less investigated. A few single case studies of patients made anarthric by focal or degenerative cortical damage, who show a pattern of impairment indicative of a deficit of PhREC, sparing the REH process, suggest that the primary motor cortex (M1) might be involved. To test this hypothesis in healthy participants with a neurophysiological approach, we measured the corticospinal excitability of M1, by means of Transcranial Magnetic Stimulation (TMS)-induced Motor Evoked Potentials (MEPs), during the execution of phonological judgements on auditorily vs. visually presented words (Experiment #1). Crucially, these phonological tasks involve REH, while PhREC is required only with visual presentation. Results show MEPs with larger amplitude when stimuli are presented visually. Task difficulty does not account for this difference and the result is specific for linguistic stimuli, indeed visual and auditory stimuli that cannot be verbalized lead to different behavioral and neurophysiological patterns (Experiment #2). The increase of corticospinal excitability when words are presented visually can be then interpreted as an indication of the involvement of M1 in PhREC. The present findings elucidate the neural correlates of PhREC, suggesting an involvement of the peripheral motor system in its activity.

Orthographic texture effects during spelling are due to variations in representational strength

In this study, we investigated the source of the orthographic texture effect during familiar word spelling. Orthographic texture refers to the differential strength that individual letters in a word may be activated for output. Prior work indicates that strongly activated letters are more accurately produced than weakly activated ones (Jones, Folk, & Rapp, 2009, All Letters are not Equal: Sub-Graphemic Texture in Orthographic Working Memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 35, 1389-1402. DOI: 10.1037/a0017042). According to an orthographic lexical strength account, differences in activation of individual letters within words are the result of learning; more easily learned letters are more strongly represented and, thus, activated for output. However, an online-competition hypothesis indicates that the contribution of sublexical assembly processes during familiar word spelling may account for the effect. Current results support the orthographic lexical strength account; the lexical orthographic representations used for spelling are themselves textured.

Non-word writing does not require the phonological output buffer: Neuropsychological evidence for a direct phonological-orthographic route

What is the route that is used for writing non-words to dictation? Does it have to pass through phonological output? Two possibilities are found in the literature. In one, writing non-words requires access from the phonological input buffer to the phonological output buffer and from there, via phoneme-to-grapheme conversion, to the orthographic output buffer. The second approach maintains that writing non-words can proceed directly from the phonological input buffer to the orthographic output buffer. In this study, we discriminate between these two options using a cognitive neuropsychological approach. Specifically, we present a multiple case study of 24 individuals with a developmental impairment to the phonological output buffer, who nevertheless show unimpaired non-word writing. These data lead to the conclusion that the phonological output buffer is not necessary when writing non-words and that writing non-words to dictation can proceed directly from the phonological input buffer to the orthographic output buffer. We suggest that the cognitive assumption that non-word writing proceeds through the phonological output buffer may have resulted from graphic conventions and the depiction of the lexical processing model: in the common depiction of the model drawing a line through the phonological output buffer is visually simpler than a direct line (which would require lines to cross or long bypass lines).

A deficit in post-graphemic writing processes: Evidence for a graphomotor buffer

Post-graphemic writing processes transform abstract letter representations into representations of writing movements. We describe an individual with an acquired post-graphemic writing deficit. NGN is normal in spelling words aloud, but impaired in writing words to dictation, with most errors involving letter substitutions (e.g., RUMOR written as BUMOR). NGN's deficit affects graphic motor plans, which specify the writing strokes for producing letters. Analyses of writing speed, fluency, and stroke patterns suggest that NGN's errors result from incomplete motor-plan activation. NGN's error rate is high for the first letter in a word, and declines across subsequent positions. On the basis of this serial position effect and other results, we propose that post-graphemic writing mechanisms include a graphomotor buffer, a writing-specific working memory that holds activated graphic motor plans bound to specific serial positions. We suggest that NGN's graphomotor buffer is damaged such that early serial positions are affected most severely. Finally, we present results speaking to the roles and capabilities of the graphomotor buffer, and the structure of graphic motor plans.

Understanding handwriting difficulties: A comparison of children with and without motor impairment

The nature of handwriting difficulties have been explored in children with specific developmental disorders. The aim of this study was to investigate the nature of handwriting difficulties in children with dysgraphia, a less studied group who have significant handwriting difficulties in the absence of motor control or cognitive difficulties. The performance of a dysgraphia group aged 8-14 years was compared to a group with Developmental Coordination Disorder and to typically developing (TD) controls. Participants completed two handwriting tasks on a digitizing writing tablet. The amount and accuracy of the handwriting product was measured, plus various temporal and spatial features of the writing process. There were no significant differences in performance between the two groups with handwriting difficulties but both performed more poorly than the TD group. Individual differences in the type and severity of handwriting impairments suggest the need for a range of classroom assessments to tailor intervention appropriately.

Developmental graphemic buffer dysgraphia in English: A single case study

A single case study is reported of a 10-year-old, English-speaking boy, L.S., who presented with spelling errors similar to those described in acquired graphemic buffer dysgraphia (GBD). We used this case to evaluate the appropriateness of applying adult cognitive models to the investigation of developmental cognitive disorders. The dual-route model of spelling guided this investigation. L.S. primarily made "letter errors" (deletions, additions, substitutions, transpositions, or a combination of these errors) on words and nonwords and in all input (aural and visual) and output modalities (writing, typing, oral spelling); there was also some evidence of a length effect and U-shaped serial position curve. An effect of lexical variables on spelling performance was also found. We conclude that the most parsimonious account is an impairment at the level of the graphemic buffer and without systematic cognitive neuropsychological investigation, the nature of L.S.'s spelling difficulty would likely have been missed.

Developmental dysgraphia: An overview and framework for research

Developmental deficits in the acquisition of writing skills (developmental dysgraphias) are common and have significant consequences, yet these deficits have received relatively little attention from researchers. We offer a framework for studying developmental dysgraphias (including both spelling and handwriting deficits), arguing that research should be grounded in theories describing normal cognitive writing mechanisms and the acquisition of these mechanisms. We survey the current state of knowledge concerning developmental dysgraphia, discussing potential proximal and distal causes. One conclusion emerging from this discussion is that developmental writing deficits are diverse in their manifestations and causes. We suggest an agenda for research on developmental dysgraphia, and suggest that pursuing this agenda may contribute not only to a better understanding of developmental writing impairment, but also to a better understanding of normal writing mechanisms and their acquisition. Finally, we provide a brief introduction to the subsequent articles in this special issue on developmental dysgraphia.

Fluency and Accuracy in Alphabet Writing by Keyboarding: A Cross-Sectional Study in Spanish-Speaking Children With and Without Learning Disabilities

The aim of this study was to analyze whether children with and without difficulties in handwriting, spelling, or both differed in alphabet writing when using a keyboard. The total sample consisted of 1,333 children from Grades 1 through 3. Scores on the spelling and handwriting factors from the Early Grade Writing Assessment (Jiménez, in press) were used to assign the participants to one of four groups with different ability patterns: poor handwriters, poor spellers, a mixed group, and typically achieving students. Groups were equalized by a matching strategy, resulting in a final sample of 352 children. A MANOVA was executed to analyze effects of group and grade on orthographic motor integration (fluency of alphabet writing) and the number of omissions when writing the alphabet (accuracy of alphabet writing) by keyboard writing mode. The results indicated that poor handwriters did not differ from typically achieving children in both variables, whereas the poor spellers did perform below the typical achievers and the poor handwriters. The difficulties of poor handwriters seem to be alleviated by the use of the keyboard; however, children with spelling difficulties might need extra instruction to become fluent keyboard writers.

Internal Structure and Development of Keyboard Skills in Spanish-Speaking Primary-School Children With and Without LD in Writing

This study had two purposes: examining the internal structure of the Test Estandarizado para la Evaluación Inicial de la Escritura con Teclado (TEVET; Spanish Keyboarding Writing Test), and analyzing the development of keyboarding skills in Spanish elementary school children with and without learning disabilities (LD) in writing. A group of 1,168 elementary school children carried out the following writing tasks: writing the alphabet in order from memory, allograph selection, word copying, writing dictated words with inconsistent spelling, writing pseudowords from dictation, and independent composition of sentence. For this purpose, exploratory factor analysis for the TEVET was conducted. Principal component analysis with a varimax rotation identified three factors with eigenvalues greater than 1.0. Based on factorial analysis, we analyzed the keyboarding skills across grades in Spanish elementary school children with and without LD (i.e., poor handwriters compared with poor spellers, who in turn were compared with mixed compared with typically achieving writers). The results indicated that poor handwriters did not differ from typically achieving writers in phonological processing, visual-orthographic processing, and sentence production components by keyboarding. The educational implications of the findings are analyzed with regard to acquisition of keyboarding skills in children with and without LD in transcription.

Do reading and spelling share a lexicon?

In the reading and spelling literature, an ongoing debate concerns whether reading and spelling share a single orthographic lexicon or rely upon independent lexica. Available evidence tends to support a single lexicon account over an independent lexica account, but evidence is mixed and open to alternative explanation. In the current work, we propose another, largely ignored account--separate-but-shared lexica--according to which reading and spelling have separate orthographic lexica, but information can be shared between them. We report three experiments designed to competitively evaluate these three theoretical accounts. In each experiment, participants learned new words via reading training and/or spelling training. The key manipulation concerned the amount of reading versus spelling practice a given item received. Following training, we assessed both response time and accuracy on final outcome measures of reading and spelling. According to the independent lexica account, final performance in one modality will not be influenced by the level of practice in the other modality. According to the single lexicon account, final performance will depend on the overall amount of practice regardless of modality. According to the separate-but-shared account, final performance will be influenced by the level of practice in both modalities but will benefit more from same-modality practice. Results support the separate-but-shared account, indicating that reading and spelling rely upon separate lexica, but information can be shared between them.

Acquired dysgraphia in adults following right or left-hemisphere stroke

Objective

This study aimed to assess the strengths and difficulties in word and pseudoword writing in adults with left- and right-hemisphere strokes, and discuss the profiles of acquired dysgraphia in these individuals.

Methods

The profiles of six adults with acquired dysgraphia in left- or right-hemisphere strokes were investigated by comparing their performance on word and pseudoword writing tasks against that of neurologically healthy adults. A case series analysis was performed on the patients whose impairments on the task were indicative of acquired dysgraphia.

Results

Two patients were diagnosed with lexical dysgraphia (one with left hemisphere damage, and the other with right hemisphere damage), one with phonological dysgraphia, another patient with peripheral dysgraphia, one patient with mixed dysgraphia and the last with dysgraphia due to damage to the graphemic buffer. The latter patients all had left-hemisphere damage (LHD). The patterns of impairment observed in each patient were discussed based on the dual-route model of writing.

Conclusion

The fact that most patients had LHD rather than right-hemisphere damage (RHD) highlights the importance of the former structure for word processing. However, the fact that lexical dysgraphia was also diagnosed in a patient with RHD suggests that these individuals may develop writing impairments due to damage to the lexical route, leading to heavier reliance on phonological processing. Our results are of significant importance to the planning of writing interventions in neuropsychology.

Morphological-compound dysgraphia in an aphasic patient: "A wild write through the lexicon"

We describe the case of a dysgraphic aphasic individual--S.G.W.--who, in writing to dictation, produced high rates of formally related errors consisting of both lexical substitutions and what we call morphological-compound errors involving legal or illegal combinations of morphemes. These errors were produced in the context of a minimal number of semantic errors. We could exclude problems with phonological discrimination and phonological short-term memory. We also excluded rapid decay of lexical information and/or weak activation of word forms and letter representations since S.G.W.'s spelling showed no effect of delay and no consistent length effects, but, instead, paradoxical complexity effects with segmental, lexical, and morphological errors that were more complex than the target. The case of S.G.W. strongly resembles that of another dysgraphic individual reported in the literature--D.W.--suggesting that this pattern of errors can be replicated across patients. In particular, both patients show unusual errors resulting in the production of neologistic compounds (e.g., "bed button" in response to "bed"). These patterns can be explained if we accept two claims: (a) Brain damage can produce both a reduction and an increase in lexical activation; and (b) there are direct connections between phonological and orthographic lexical representations (a third spelling route). We suggest that both patients are suffering from a difficulty of lexical selection resulting from excessive activation of formally related lexical representations. This hypothesis is strongly supported by S.G.W.'s worse performance in spelling to dictation than in written naming, which shows that a phonological input, activating a cohort of formally related lexical representations, increases selection difficulties.

The analysis of perseverations in acquired dysgraphia reveals the internal structure of orthographic representations

At a minimum, our long-term memory representations of word spellings consist of ordered strings of single letter identities. While letter identity and position must certainly be represented, it is by no means obvious that this is the only information that is included in orthographic representations, nor that representations necessarily have a one-dimensional "flat" structure. Evidence favours the alternative hypothesis that orthographic representations, much like phonological ones, are internally rich, complex multidimensional structures, though many questions remain regarding the precise nature of the internal complexity of orthographic representations. In this investigation, we test competing accounts of the internal structure of orthographic representations by analysing the perseveration errors produced by an individual with acquired dysgraphia, L.S.S. The analysis of perseveration errors provides a novel and powerful method for investigating the question of the independence of different representational components. The results provide clear support for the hypothesis that letter quantity and syllabic role information are associated with, but separable from, letter identity information. Furthermore, the results indicate that digraphs-letter pairs associated with a single phoneme (e.g., the SH in FISH)-are units of orthographic representation. These results contribute substantially to the further development of the multidimensional hypothesis, providing both new and converging evidence regarding the nature of the internal complexity of orthographic representations.

Temporal stability and representational distinctiveness: key functions of orthographic working memory

A primary goal of working memory research has been to understand the mechanisms that permit working memory systems to effectively maintain the identity and order of the elements held in memory for sufficient time as to allow for their selection and transfer to subsequent processing stages. Based on the performance of two individuals with acquired dysgraphia affecting orthographic working memory (WM; the graphemic buffer), we present evidence of two distinct and dissociable functions of orthographic WM. One function is responsible for maintaining the temporal stability of letters held in orthographic WM, while the other is responsible for maintaining their representational distinctiveness. The failure to maintain temporal stability and representational distinctiveness gives rise, respectively, to decay and interference effects that manifest themselves in distinctive error patterns, including distinct serial position effects. The findings we report have implications beyond our understanding of orthographic WM, as the need to maintain temporal stability and representational distinctiveness in WM is common across cognitive domains.

Underlying cause(s) of letter perseveration errors

Perseverations, the inappropriate intrusion of elements from a previous response into a current response, are commonly observed in individuals with acquired deficits. This study specifically investigates the contribution of failure-to activate and failure-to-inhibit deficit(s) in the generation of letter perseveration errors in acquired dysgraphia. We provide evidence from the performance 12 dysgraphic individuals indicating that a failure to activate graphemes for a target word gives rise to letter perseveration errors. In addition, we also provide evidence that, in some individuals, a failure-to-inhibit deficit may also contribute to the production of perseveration errors.

Inflectional spelling deficits in developmental dyslexia

The goal of this study was to examine past-tense spelling deficits in developmental dyslexia and their relationship to phonological abilities, spoken morphological awareness and word specific orthographic memory. Three groups of children (28 9-year-old dyslexic, 28 chronological age-matched and 28 reading/spelling age-matched children) completed a battery of tests including spelling regularly inflected words (e.g., kissed) and matched one-morpheme words (e.g., wrist). They were also assessed on a range of tests of reading and spelling abilities and associated linguistic measures. Dyslexic children were impaired in relation to chronological age-matched controls on all measures. Furthermore, they were significantly poorer than younger reading and spelling age-matched controls at spelling inflected verbs, supporting the existence of a specific deficit in past-tense spelling in dyslexia. In addition to under-using the -ed spelling on inflected verbs, the dyslexic children were less likely to erroneously apply this spelling to one-morpheme words than younger controls. Dyslexics were also poorer than younger controls at using a consistent spelling for stems presented in isolation versus as part of an inflected word, indicating that they make less use of the morphological relations between words to support their spelling. In line with this interpretation, regression analyses revealed another qualitative difference between the spelling and reading age-matched group and the dyslexic group: while both spoken morphological awareness and orthographic word specific memory were significant predictors of the accuracy of past-tense spelling in the former group, only orthographic memory (irregular word reading and spelling) was a significant factor in the dyslexic group. Finally, we identified a subgroup of seven dyslexic children who were severely deficient in past-tense spelling. This subgroup was also significantly worse than other dyslexics and than younger controls on scores of orthographic memory. The implications of our findings for teaching and remediation strategies are discussed.

Representation of letter position in spelling: evidence from acquired dysgraphia

The graphemic representations that underlie spelling performance must encode not only the identities of the letters in a word, but also the positions of the letters. This study investigates how letter position information is represented. We present evidence from two dysgraphic individuals, CM and LSS, who perseverate letters when spelling: that is, letters from previous spelling responses intrude into subsequent responses. The perseverated letters appear more often than expected by chance in the same position in the previous and subsequent responses. We used these errors to address the question of how letter position is represented in spelling. In a series of analyses we determined how often the perseveration errors produced maintain position as defined by a number of alternative theories of letter position encoding proposed in the literature. The analyses provide strong evidence that the grapheme representations used in spelling encode letter position such that position is represented in a graded manner based on distance from both-edges of the word.

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.

Is compound chaining the serial-order mechanism of spelling? A simple recurrent network investigation

Although considerable progress has been made in determining the cognitive architecture of spelling, less is known about the serial-order mechanism of spelling: the process(es) involved in producing each letter in the proper order. In this study, we investigate compound chaining as a theory of the serial-order mechanism of spelling. Chaining theories posit that the retrieval from memory of each element in a sequence is dependent upon the retrieval of previous elements. We examine this issue by comparing the performance of simple recurrent networks (a class of neural networks that we show can operate by chaining) with that of two individuals with acquired dysgraphia affecting the serial-order mechanism of spelling-the graphemic buffer. We compare their performance in terms of the effects of serial position, the effect of length on overall letter accuracy, and the effect of length on the accuracy of specific positions within the word. We find that the networks produce significantly different patterns of performance from those of the dysgraphics, indicating that compound chaining is not an appropriate theory of the serial-order mechanism of spelling.

Architectures, representations and processes of language production

We present an overview of recent research conducted in the field of language production based on papers presented at the first edition of the International Workshop on Language Production (Marseille, France, September 2004). This article comprises two main parts. In the first part, consisting of three sections, we review the articles that are included in this Special Issue. These three sections deal with three different topics of general interest for models of language production: (A) the general organisational principles of the language production system, (B) several aspects of the lexical selection process and (C) the representations and processes used during syntactic encoding. In the second part, we discuss future directions for research in the field of language production, given the considerable developments that have occurred in recent years.