The impact of deep dysgraphia on graphemic buffer disorders

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.

Distinct Neural Substrates Support Phonological and Orthographic Working Memory: Implications for Theories of Working Memory

Prior behavioral and neuroimaging evidence supports a separation between working memory capacities in the phonological and orthographic domains. Although these data indicate distinct buffers for orthographic and phonological information, prior neural evidence does indicate that nearby left inferior parietal regions support both of these working memory capacities. Given that no study has directly compared their neural substrates based on data from the same individuals, it is possible that there is a common left inferior parietal region shared by both working memory capacities. In fact, those endorsing an embedded processes account of working memory might suggest that parietal involvement reflects a domain-general attentional system that directs attention to long-term memory representations in the two domains, implying that the same neural region supports the two capacities. Thus, in this work, a multivariate lesion-symptom mapping approach was used to assess the neural basis of phonological and orthographic working memory using behavioral and lesion data from the same set of 37 individuals. The results showed a separation of the neural substrates, with regions in the angular gyrus supporting orthographic working memory and with regions primarily in the supramarginal gyrus supporting phonological working memory. The results thus argue against the parietal involvement as supporting a domain-general attentional mechanism and support a domain-specific buffer account of working memory.

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.

Children Learn to Read: How Visual Analysis and Mental Imagery Contribute to the Reading Performances at Different Stages of Reading Acquisition

Reading in alphabetic orthography requires analysis and recognition of specific attributes of visual stimuli, and generation, reactivation, and use of mental images of letters and words. This study evaluated the role of visual analysis and mental imagery in reading performances of students at different stages of reading acquisition. Reading "comprehension," "accuracy," and "speed," were analyzed. Participants were 90 children who attended primary school. Children were assessed in the first and third grade. The results highlighted that mental imagery and visual analysis influenced reading acquisition. These abilities are differently involved in the three dimensions of reading skill. The issues of this study have practical and educational applications. The early assessment of visual analysis and mental imagery skills and specific training on these abilities could contribute to facilitate reading acquisition. Strategies of intervention centered on visual imagery could increase reading performances in typically developing children and children at risk of learning difficulties.

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).

Non-linear spelling in writing after a pure cerebellar lesion

The most common deficits in processing written language result from damage to the graphemic buffer system and refer to semantic and lexical problems or difficulties in phoneme-graphene conversion. However, a writing disorder that has not yet been studied in depth is the non-linear spelling phenomenon. Indeed, although some cases have been described, no report has exhaustively explained the cognitive mechanism and the anatomical substrates underlying this process. In the present study, we analyzed the modality of non-linear writing in a patient affected by a focal cerebellar lesion, who presented with an alteration of the normal trend to write the order of the letters. Based on this evidence, we analyzed the functional connectivity between the cerebellum and the brain network that subtends handwriting and demonstrated how the cerebellar lesion of the patient affected the connections between the cerebellum and cortical areas that support the anatomical system of writing. This is the first report of non-linear spelling in a patient with a lesion outside the fronto-parietal network, specifically with a focal cerebellar lesion. We propose that non-linear writing can be interpreted in view of the role of the cerebellum in timing and sequential processing. Thus, considering the current functional connectivity data, we hypothesize that the cerebellum might be relevant in the mechanism that allows the correct activation timing of letters within a string and placement of the letters in a specific sequential writing order.

Mental Imagery and School Readiness

The aim of this study was to investigate the relationships between the skills that constitute school readiness, such as linguistic, phonological, logical-mathematical and psychomotor skills, and mental imagery processes in preschool children. The participants were 100 healthy children (50 boys and 50 girls) aged four to five. Two batteries of tests were used to assess school readiness and different aspects of the mental imagery processes. The mental imagery battery measured mental imagery generation, inspection, and rotation of images. The results showed a relationship between the generation and inspection processes and the level of skills that constitute school readiness. These findings emphasize the potential usefulness of screening all preschoolers and kindergarteners for imagery ability, with the aim of adopting effective measures to increase their mental imagery abilities.

Cognitive neuropsychological analysis of differential reading and spelling disorder mechanisms in a patient with aphasia

The purpose of this study was to determine if differential reading and spelling mechanisms were involved in a Japanese patient with aphasia. In our case, the patient scored low on all of the administered reading tasks, suggesting that both the reading lexical and non-lexical routes were impaired. In contrast, his writing-to-dictation score for Kana nonwords was high, suggesting that the spelling non-lexical route was intact. However, the patient scored low on a writing-to-dictation task comprised of high-familiarity Kanji words. The spelling lexical route was thought to be impaired. Therefore, the mechanism(s) involved in reading and spelling may differ in this case.

Cascading activation from lexical processing to letter-level processing in written word production

Descriptions of language production have identified processes involved in producing language and the presence and type of interaction among those processes. In the case of spoken language production, consensus has emerged that there is interaction among lexical selection processes and phoneme-level processing. This issue has received less attention in written language production. In this paper, we present a novel analysis of the writing-to-dictation performance of an individual with acquired dysgraphia revealing cascading activation from lexical processing to letter-level processing. The individual produced frequent lexical-semantic errors (e.g., chipmunk → SQUIRREL) as well as letter errors (e.g., inhibit → INBHITI) and had a profile consistent with impairment affecting both lexical processing and letter-level processing. The presence of cascading activation is suggested by lower letter accuracy on words that are more weakly activated during lexical selection than on those that are more strongly activated. We operationalize weakly activated lexemes as those lexemes that are produced as lexical-semantic errors (e.g., lethal in deadly → LETAHL) compared to strongly activated lexemes where the intended target word (e.g., lethal) is the lexeme selected for production.

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.

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 ) 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.

Distinctions between orthographic long-term memory and working memory

Research in the cognitive and neural sciences has long posited a distinction between the long-term memory (LTM) storage of information and the short-term buffering of information that is being actively manipulated in working memory (WM). This basic type of distinction has been posited in a variety of domains, including written language production-spelling. In the domain of spelling, the primary source of empirical evidence regarding this distinction has been cognitive neuropsychological studies reporting deficits selectively affecting what the cognitive neuropsychological literature has referred to as the orthographic lexicon (LTM) or the graphemic buffer (WM). Recent papers have reexamined several of the hallmark characteristics of impairment affecting the graphemic buffer, with implications for our understanding of the nature of the orthographic LTM and WM systems. In this paper, we present a detailed case series study of 4 individuals with acquired spelling deficits and report evidence from both error types and factors influencing error rates that support the traditional distinction between these cognitive systems involved in spelling. In addition, we report evidence indicating possible interaction between these systems, which is consistent with a variety of recent findings in research on spelling.

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.

Dysgraphia in dementia: a systematic investigation of graphemic buffer features in a case series

In this paper we report findings from a systematic investigation of spelling performance in three patients - PR, RH and AC - who despite their different medical diagnoses showed a very consistent pattern of dysgraphia, more typical of graphemic buffer disorder. Systematic investigation of the features characteristic of this disorder in Study 1 confirmed the presence of length effects in spelling, classic errors (i.e., letter substitution, omission, addition, transposition), a bow-shaped curve in the serial position of errors and consistency in substitution of consonants and vowels. However, in addition to this clear pattern of graphemic buffer impairment, evidence of regularity effects and phonologically plausible errors in spelling raised questions about the integrity of the lexical spelling route in each case. A second study was conducted, using a word and non-word immediate delay copy task, in an attempt to minimise the influence of orthographic representations on written output. Persistence of graphemic buffer errors would suggest an additional, independent source of damage. Two patients, PR and AC, took part and in both cases symptoms of graphemic buffer disorder persisted. Together, these findings suggest that damage to the graphemic buffer may be more common than currently suggested in the literature.

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.