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.     

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.     

Allographic agraphia: a case study

We report the case of patient MN, diagnosed with frontotemporal dementia, who exhibited a severe impairment in writing letters and words in upper-case print in the face of accurate production of the same stimuli in lower-case cursive. In contrast to her written production difficulties, MN was unimpaired in recognizing visually presented letters and words in upper-case print. We find a modest benefit of visual form cueing in the written production of upper-case letters, despite an inability to describe or report visual features of letters in any case or font. This case increases our understanding of the allographic level of letter-shape representation in written language production. It provides strong support for previous reports indicating the neural independence of different types of case and font-specific letter-shape information; it provides evidence that letter-shape production does not require explicit access to information about the visual attributes of letter shapes and, finally, it reveals the possibility of interaction between processes involved in letter-shape production and perception.     

Pure agraphia after infarction in the superior and middle portions of the left precentral gyrus: Dissociation between Kanji and Kana

The present study describes a Japanese patient with pure agraphia displaying differential disturbances in processing Kanji (morphogram) and Kana (syllabogram) letters after an infarction in the middle and superior portions of the left precentral gyrus. Kana errors reflected the patient’s difficulty with retrieving both motor and visual letter images, whereas Kanji errors included partial letter stroke omissions or additions. This present case suggests that differences in writing disturbances between Kana and Kanji letters are caused by a differential dependency on letter motor images.     

The impact of deep dysgraphia on graphemic buffer disorders

This article describes an investigation into the residual writing skills of a severely dysgraphic patient (DA). We found that they were powerfully influenced by a number of lexical variables (lexicality, frequency, imageability, length and geminates). His error pattern was characterized by semantic, lexical, substitution, deletion errors and fragment responses that preserved the first letter. Thus, DA's written spelling was characterized by both deep dysgraphic and graphemic output buffer effects. It is proposed that this pattern of performance represents a new"putative functional syndrome."     

Mirror writing and reversing single letters in stroke patients and normal elderly

Abstract Mirror writing (MW) refers to the production of individual letters or whole word strings in reversed direction. When held to a mirror, these letters or words can be read normally. We observed MW in a considerable number of stroke patients. Of the 86 patients screened 15 (17.5%) showed at least one instance of mirror writing in any of the tasks. Both right (14% of 36 patients) and left (20% of 50 patients) hemisphere damaged patients produced reversed letters only when writing with their left hand, respectively the contralesional and ipsilesional hand. The dissociated performance between the two hands in brain damaged patients is relevant to the interpretation of MW because, unlike all other peripheral dysgraphias, MW affects the non-dominant hand only. Importantly, healthy elderly also showed MW solely when writing with their left hand (6.9% of 86 participants). MW in controls was less frequent but qualitatively similar to that observed in brain damaged patients. This finding is consistent with the motor interpretation of MW that assumes an inability to transform the stored letter forming programmes for left hand writing. However, several cases have been reported in the literature of a more pervasive form of MW whereby patients mirror reverse entire words or sentences. This pattern has been observed in children learning to write but it has never been observed in healthy adult volunteers. We propose that the diagnosis of MW should be limited to the reversal of whole words, multi-digit numbers and full sentences, which reveal a disorder in coding the correct direction of writing rather than an inability to accomplish the correct spatial orientation of single letters.     

The development of writing skills in 4-year-old children with and without specific language impairment

ABSTRACT

Research shows that many preschool children with specific language impairment (SLI) have difficulty acquiring literacy skills including phonological awareness, print concepts, and alphabet knowledge. Limited research suggests that preschool children with SLI also have difficulty with emergent writing tasks such as name writing and word writing. In typically developing children, research indicates that emergent writing skills are acquired in a developmental sequence: (1) linearity, (2) segmentation, (3) simple characters, (4) left-right orientation, (5) complex characters, (6) random letters, and (7) invented spelling. This study compared the emergent writing skills of 4-year-old children with SLI (n = 22) to their age- and gender-matched peers (n = 22). Results indicated that children with SLI demonstrate difficulty with a variety of writing tasks, including letter writing, name writing, word writing, and sentence writing when compared to their typically-developing peers. Children with SLI followed the same developmental sequence in acquiring writing skills as their typically-developing peers.     

Neglect dysgraphia.

A phonological dysgraphic syndrome is documented in a left handed man with a right-hemisphere lesion. His spelling was significantly affected by word length but neither word frequency nor the orthographical irregularity or word class proved to be relevant variables. Words were spelled equally efficiently forwards as backwards. A clear gradient of letter errors was shown to exist with letters on the left being mis-spelled more often than letters on the right of a word, irrespective of word length. These findings are discussed in terms of current models of spelling and their relevance to theories of unilateral neglect.     

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.     

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.     

Developmental attentional dyslexia

Attentional dyslexia is a reading deficit in which letters migrate between neighboring words, but are correctly identified and keep their correct relative position within the word. Thus, for example, fig tree can be read as fig free or even tie free. This study reports on 10 Hebrew-speaking individuals with developmental attentional dyslexia and explores in detail the characteristics of their between-word errors. Each participant read 2290 words, presented in word pairs: 845 horizontally presented word pairs, 240 vertically presented word pairs, and 60 nonword pairs. The main results are that almost all migrations preserve the relative position of the migrating letter within the word, indicating that the between-word position can be impaired while the within-word position encoding remains intact. This result is also supported by the finding that the participants did not make many letter position errors within words. Further analyses indicated that more errors occur in longer words, that most migrations occur in final letters (which are the leftmost letters in Hebrew), and that letters migrate both horizontally and vertically, and more frequently from the first to the second word in horizontal presentation. More migrations occurred when the result of migration was an existing word. Similarity between words in a pair did not increase error rates, and more migrations occurred when the words shared fewer letters. The between-word errors included the classic errors of migration of a letter between words, but also omission of one instance of a letter that appeared in the same position in the two words, an error that constituted a considerable percentage of the between-word errors, and intrusion of a letter from one word to the corresponding position in the neighboring word without erasing the original letter in the same position.     

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.     

When ‘slime’ becomes ‘smile’: Developmental letter position dyslexia in English

We report the first three cases of selective developmental letter position dyslexia in English. Although the parents and teachers of the children were concerned about these children's reading, standard tests did not reveal their deficit. It was only when the appropriate target words were presented, in this case, migratable words, that their letter position dyslexia was detected. Whereas previous research has described cases with acquired and developmental forms of letter position dyslexia in Hebrew and Arabic readers, this is the first report of this type of reading disorder in English. The cardinal symptom of letter position dyslexia is the migration of letters within the word (reading slime as ‘smile’; pirates as ‘parties’). These migration errors occur in reading aloud as well as in tasks of silent reading. This study provides further evidence that migration errors emerge at the level of early visual-orthographic analysis, in the letter position encoding function. Alternative explanations for the occurrence of migration errors such as poor phonological processing or a deficit in the orthographic input lexicon are ruled out.     

Letter processing automatically recruits a sensory-motor brain network

Behavioral, neuropsychological and neuroimaging research suggest a distributed network that is recruited when we interact with letters. For the first time, we combine several letter processing tasks in a single experiment to study why letters seem to engage such disparate processing areas. Using fMRI, we investigate how the brain responds to letters using tasks that should recruit systems for letter perception, letter writing, letter copying and letter imagery. We describe a network of five cortical regions including the left fusiform gyrus, two left pre-central areas, left cuneus and the left inferior frontal gyrus that are all selectively engaged during a 1-back matching paradigm with letters. Our results suggest involvement of these regions to different extents in different tasks. However, the regions also form an integrated network such that letter perception also engages motor regions while writing recruits letter-specific visual regions as well. We suggest that this distributed network is a direct result of our sensory–motor interactions with letters.     

Analysis of the spontaneous writing errors of normal and aphasic writers

Samples of spontaneous writing were collected from 150 normal subjects, 13 Broca's aphasics, 23 Wernicke's aphasics and 14 conduction aphasics. The errors obtained were classified using a system derived from investigations of slips of the pen in normal subjects. All three aphasic groups made a higher proportion of word-level errors than did the normal writers. Word-level errors tended to be selection errors (substitutions, blends, neologisms, and omissions) rather than movement errors (anticipations, perseverations and reversals). Conduction aphasics showed proportionately more letter movement and fewer letter selection errors than normal writers while Wernicke's and Broca's aphasics showed similar proportions. Graphic and phonetic similarity was no more important a determinant of letter errors in aphasics than in normals. The span of movement errors was particularly restricted in the Broca's and conduction aphasics. Asking patients to write connected text yields insight into the nature of the underlying disorder that could not be obtained from studying the writing of single words.     

Spatio-temporal dynamics of working memory maintenance and scanning of verbal information

ObjectiveDuring verbal communication, humans briefly maintain mental representations of speech sounds conveying verbal information, and constantly scan these representations for comparison to incoming information. We determined the spatio-temporal dynamics of such short-term maintenance and subsequent scanning of verbal information, by intracranially measuring high-gamma activity at 70–110 Hz during a working memory task.MethodsPatients listened to a stimulus set of two or four spoken letters and were instructed to remember those letters over a two-second interval, following which they were asked to determine if a subsequent target letter had been presented earlier in that trial’s stimulus set.ResultsAuditory presentation of letter stimuli sequentially elicited high-gamma augmentation bilaterally in the superior-temporal and pre-central gyri. During the two-second maintenance period, high-gamma activity was augmented in the left pre-central gyrus, and this effect was larger during the maintenance of stimulus sets consisting of four compared to two letters. During the scanning period following target presentation, high-gamma augmentation involved the left inferior-frontal and supra-marginal gyri.ConclusionsShort-term maintenance of verbal information is, at least in part, supported by the left pre-central gyrus, whereas scanning by the left inferior-frontal and supra-marginal gyri.SignificanceThe cortical structures involved in short-term maintenance and scanning of speech stimuli were segregated with an excellent temporal resolution.     

Neglect dyslexia and the early stages of visual word recognition

Abstract

Neglect dyslexia is an acquired reading disorder in which one side of words or letter strings is misidentified. Caramazza and Hillis (Cognitive Neuropsychology 1990; 7: 391-445) proposed that the disorder reflects an impairment in the early stages of visual word recognition. Three levels of representation are involved, each with corresponding spatial coordinates. These levels reflect a progression away from the physical stimulus toward a more abstract representation of a word. The errors made by a patient with a level one deficit are relative to the location of a word in the visual field. The errors made by a patient with a level two deficit are relative to the spatial position of a letter(s) within the stimulus. The errors made by a patient with a level three deficit are relative to the ordinal position of a letter(s) within a word. We describe how this model may be used to interpret the differing patterns of performance found in neglect dyslexia and evaluate the model according to 19 published single case studies of neglect dyslexia. It is concluded that the model is well supported by these data and may therefore be viewed as a model of the early stages of reading in intact readers.