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1.  Underlying Cause(s) of Letter Perseveration Errors 
Neuropsychologia  2011;50(2):305-318.
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.
doi:10.1016/j.neuropsychologia.2011.12.001
PMCID: PMC3259193  PMID: 22178232
letter perseveration errors; dysgraphia; spelling; inhibition
2.  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.
doi:10.1016/j.cortex.2009.12.001
PMCID: PMC2889229  PMID: 20060967
Primary Progressive Aphasia; dysgraphia; spelling errors; neuroimaging; aphasia
3.  Further evidence for the interaction of central and peripheral processes: the impact of double letters in writing English words 
Most studies on spelling processes suppose that the activation of orthographic representations is over before we start to write. The goal of the present study was to provide evidence indicating that the orthographic representations activated during spelling production interact continuously with the motor processes during movement production. We manipulated gemination to assess the influence of the orthographic properties of words on the kinematic parameters of production. Native English-speaking participants wrote words containing double letters and control words on a digitizer [e.g., DISSIPATE (Geminate) and DISGRACE (Control)]. The word pairs shared the initial letters and differed on the presence of a doublet at the same position. The results revealed that latencies were shorter for Geminates than Controls, indicating that spelling processes were facilitated by the presence of a doublet in the word. Critically, the impact of letter doubling was also observed during production, with shorter letter durations (e.g., D, I, S) and intervals (DI, IS) for Geminates than Controls. Letter doubling therefore affected the whole process of word writing: from spelling recall to movement preparation and production. The spelling processes that were involved before movement initiation cascaded into processes that regulate movement execution. The activation spread onto peripheral processing until the production of the doublet was completely programmed (e.g., letter S).
doi:10.3389/fpsyg.2013.00729
PMCID: PMC3794189  PMID: 24133473
double letters; handwriting; cascaded processing; spelling; central processing; peripheral processing
4.  Lexical neighborhood effects in pseudoword spelling 
The general aim of this study is to contribute to a better understanding of the cognitive processes that underpin skilled adult spelling. More specifically, it investigates the influence of lexical neighbors on pseudo-word spelling with the goal of providing a more detailed account of the interaction between lexical and sublexical sources of knowledge in spelling. In prior research examining this topic, adult participants typically heard lists composed of both words and pseudo-words and had to make a lexical decision to each stimulus before writing the pseudo-words. However, these priming paradigms are susceptible to strategic influence and may therefore not give a clear picture of the processes normally engaged in spelling unfamiliar words. In our two Experiments involving 71 French-speaking literate adults, only pseudo-words were presented which participants were simply requested to write to dictation using the first spelling that came to mind. Unbeknownst to participants, pseudo-words varied according to whether they did or did not have a phonological word neighbor. Results revealed that low-probability phoneme/grapheme mappings (e.g., /o/ -> aud in French) were used significantly more often in spelling pseudo-words with a close phonological lexical neighbor with that spelling (e.g., /krepo/ derived from “crapaud,” /krapo/) than in spelling pseudo-words with no close neighbors (e.g., /frøpo/). In addition, the strength of this lexical influence increased with the lexical frequency of the word neighbors as well as with their degree of phonetic overlap with the pseudo-word targets. These results indicate that information from lexical and sublexical processes is integrated in the course of spelling, and a specific theoretical account as to how such integration may occur is introduced.
doi:10.3389/fpsyg.2013.00862
PMCID: PMC3842689  PMID: 24348436
pseudoword spelling; skilled spelling; literacy; spelling models; neighborhood activation
5.  Precision of Position Signals for Letters 
Vision research  2009;49(15):1948-1960.
Accurate reading of words and text relies on reliable identification of letters in left to right order. Previous studies have shown that people often make letter-reversal errors when identifying strings of letters away from fixation. These errors contribute to a decline in letter identification performance away from fixation. This study tests the hypothesis that these errors are due to decreased precision (increased position noise) in the coding of letter position in the periphery. To test our hypothesis, we measured observers' performance for identifying pairs of adjacent letters presented within 8 letter positions left and right of fixation. The task was to name the two letters of each pair, from left to right. Responses were scored in two ways for each letter position: (1) letters were identified correctly and in the correct position, and (2) letters were identified correctly but in the wrong position. The ratio of these two scores, when subtracted from 1, gives the empirical rate of mislocation errors. Our primary finding shows that the coding of letter position becomes increasingly imprecise with distance from fixation. A model in which the encoded position of each letter is independent and Gaussian distributed, and in which the spread of the distribution governs the precision of localizing the letter accounts for the empirical rate of mislocation errors. We also found that precision of letter position coding scales with letter size but the precision does not improve with the use of a pre-cue.
doi:10.1016/j.visres.2009.05.004
PMCID: PMC2728219  PMID: 19460396
Local signs; letter reversals; letter mislocations; crowding; letter identification; pattern vision
6.  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.
PMCID: PMC1027454  PMID: 6875593
7.  Distinctions between orthographic long-term memory and working memory 
Cognitive neuropsychology  2009;26(8):724-751.
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.
doi:10.1080/02643291003707332
PMCID: PMC3145833  PMID: 20425660
Orthography; Spelling; Long-term memory; Working memory
8.  Anatomic, clinical, and neuropsychological correlates of spelling errors in Primary Progressive Aphasia 
Neuropsychologia  2012;50(8):1929-1935.
This study evaluates spelling errors in the three subtypes of primary progressive aphasia (PPA): agrammatic (PPA-G), logopenic (PPA-L), and semantic (PPA-S). Forty one PPA-patients and 36 age-matched healthy controls were administered a test of spelling. The total number of errors and types of errors in spelling to dictation of regular words, exception words and nonwords, were recorded. Error types were classified based on phonetic plausibility. In the first analysis, scores were evaluated by clinical diagnosis. Errors in spelling exception words and phonetically plausible errors were seen in PPA-S. Conversely, PPA-G was associated with errors in nonword spelling and phonetically implausible errors. In the next analysis, spelling scores were correlated to other neuropsychological language test scores. Significant correlations were found between exception word spelling and measures of naming and single word comprehension. Nonword spelling correlated with tests of grammar and repetition. Global language measures did not correlate significantly with spelling scores, however. Cortical thickness analysis based on MRI showed that atrophy in several language regions of interest were correlated with spelling errors. Atrophy in the left supramarginal gyrus and inferior frontal gyrus (IFG) pars orbitalis correlated with errors in nonword spelling, while thinning in the left temporal pole and fusiform gyrus correlated with errors in exception word spelling. Additionally, phonetically implausible errors in regular word spelling correlated with thinning in the left IFG pars triangularis and pars opercularis. Together, these findings suggest two independent systems for spelling to dictation, one phonetic (phoneme to grapheme conversion), and one lexical (whole word retrieval).
doi:10.1016/j.neuropsychologia.2012.04.017
PMCID: PMC3527105  PMID: 22579708
Dementia; Primary Progressive Aphasia; Agraphia; Cortical atrophy; Frontotemporal dementia
9.  Letter representations in writing: an fMRI adaptation approach 
Behavioral and neuropsychological research in reading and spelling has provided evidence for the role of the following types of orthographic representations in letter writing: letter shapes, letter case, and abstract letter identities. We report on the results of an fMRI investigation designed to identify the neural substrates of these different representational types. Using an fMRI adaptation paradigm we examined the neural distribution of inhibition and release from inhibition in a letter-writing task in which, on every trial, participants produced three repetitions of the same letter and a fourth letter that was either identical to (no-change trial) or different from the previous three (change trial). Change trials involved a change in the shape, case, and/or identity of the letter. After delineating the general letter writing network by identifying areas that exhibited significant neural adaptation effects on no-change trials, we used deconvolution analysis to examine this network for effects of release from inhibition on change trials. In this way we identified regions specifically associated with the representation of letter shape (in the left SFS and SFG/pre-CG) and letter identity [in the left fusiform gyrus (FG)] or both [right cerebellum, left post-central gyrus (post-CG), and left middle frontal gyrus (MFG)]. No regions were associated with the representation of letter case. This study showcases an investigational approach that allows for the differentiation of the neurotopography of the representational types that are key to our ability to produce written language.
doi:10.3389/fpsyg.2013.00781
PMCID: PMC3809555  PMID: 24194724
letter; writing; fMRI; fMRI adaptation; neural habituation; letter shape; letter identity; letter case
10.  Linguistic Pattern Analysis of Misspellings of Typically Developing Writers in Grades 1 to 9 
Purpose
A mixed methods approach, evaluating triple word form theory, was used to describe linguistic patterns of misspellings.
Method
Spelling errors were taken from narrative and expository writing samples provided by 888 typically developing students in grades 1–9. Errors were coded by category (phonological, orthographic, and morphological) and specific linguistic feature affected. Grade level effects were analyzed with trend analysis. Qualitative analyses determined frequent error types and how use of specific linguistic features varied across grades.
Results
Phonological, orthographic, and morphological errors were noted across all grades, but orthographic errors predominated. Linear trends revealed developmental shifts in error proportions for the orthographic and morphological categories between grades 4–5. Similar error types were noted across age groups but the nature of linguistic feature error changed with age.
Conclusions
Triple word-form theory was supported. By grade 1, orthographic errors predominated and phonological and morphological error patterns were evident. Morphological errors increased in relative frequency in older students, probably due to a combination of word-formation issues and vocabulary growth. These patterns suggest that normal spelling development reflects non-linear growth and that it takes a long time to develop a robust orthographic lexicon that coordinates phonology, orthography, and morphology and supports word-specific, conventional spelling.
doi:10.1044/1092-4388(2012/10-0335)
PMCID: PMC3517694  PMID: 22473834
Spelling; triple word form theory; spelling errors; non-linear development
11.  How does graphotactic knowledge influence children's learning of new spellings? 
Two experiments investigated whether and how the learning of spellings by French third graders is influenced by two graphotactic patterns: consonants cannot double in word-initial position (Experiment 1) and consonants cannot double after single consonants (Experiment 2). Children silently read meaningful texts that contained three types of novel spellings: no doublet (e.g., mupile, guprane), doublet in a legal position (e.g., muppile, gupprane), and doublet in an illegal position (e.g., mmupile, guprrane). Orthographic learning was assessed with a task of spelling to dictation. In both experiments, children recalled items without doublets better than items with doublets. In Experiment 1, children recalled spellings with a doublet in illegal word-initial position better than spellings with a doublet in legal word-medial position, and almost all misspellings involved the omission of the doublet. The fact that the graphotactic violation in an item like mmupile was in the salient initial position may explain why children often remembered both the presence and the position of the doublet. In Experiment 2, children recalled non-words with a doublet before a single consonant (legal, e.g., gupprane) better than those with a doublet after a single consonant (illegal, e.g., guprrane). Omission of the doublet was the most frequent error for both types of items. Children also made some transposition errors on items with a doublet after a single consonant, recalling for example gupprane instead of guprrane. These results suggest that, when a doublet is in the hard-to-remember medial position, children sometimes remember that an item contains a doublet but not which letter is doubled. Their knowledge that double consonants can occur before but not after single consonants leads to transposition errors on items like guprrane. These results shed new light on the conditions under which children use general knowledge about the graphotactic patterns of their writing system to reconstruct spellings.
doi:10.3389/fpsyg.2013.00701
PMCID: PMC3790077  PMID: 24109466
spelling; graphotacics; implicit learning; statistical learning; orthographic learning
12.  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.
Images
PMCID: PMC491770  PMID: 6663305
13.  Are All Letters Really Processed Equally and in Parallel? Further Evidence of a Robust First Letter Advantage 
Acta psychologica  2013;144(2):10.1016/j.actpsy.2013.07.018.
This present study examined accuracy and response latency of letter processing as a function of position within a horizontal array. In a series of 4 Experiments, target-strings were briefly (33 ms for Experiment 1 to 3, 83 ms for Experiment 4) displayed and both forward and backward masked. Participants then made a two alternative forced choice. The two alternative responses differed just in one element of the string, and position of mismatch was systematically manipulated. In Experiment 1, words of different lengths (from 3 to 6 letters) were presented in separate blocks. Across different lengths, there was a robust advantage in performance when the alternative response was different for the letter occurring at the first position, compared to when the difference occurred at any other position. Experiment 2 replicated this finding with the same materials used in Experiment 1, but with words of different lengths randomly intermixed within blocks. Experiment 3 provided evidence of the first position advantage with legal nonwords and strings of consonants, but did not provide any first position advantage for non-alphabetic symbols. The lack of a first position advantage for symbols was replicated in Experiment 4, where target-strings were displayed for a longer duration (83 ms). Taken together these results suggest that the first position advantage is a phenomenon that occurs specifically and selectively for letters, independent of lexical constraints. We argue that the results are consistent with models that assume a processing advantage for coding letters in the first position, and are inconsistent with the commonly held assumption in visual word recognition models that letters are equally processed in parallel independent of letter position.
doi:10.1016/j.actpsy.2013.07.018
PMCID: PMC3859888  PMID: 24012723
letter-processing; serial position; visual word recognition
14.  ERP correlates of letter identity and letter position are modulated by lexical frequency 
Brain and language  2013;125(1):11-27.
The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created two pseudowords: A transposed-letter (TL: BRIGDE) and a replaced-letter pseudoword (RL: BRITGE). ERPs were recorded while participants read words and pseudowords in two tasks: Semantic categorization (Experiment 1) and lexical decision (Experiment 2). For high-frequency stimuli, similar ERPs were obtained for words and TL-pseudowords, but the N400 component to words was reduced relative to RL-pseudowords, indicating less lexical/semantic activation. In contrast, TL- and RL-pseudowords created from low-frequency stimuli elicited similar ERPs. Behavioral responses in the lexical decision task paralleled this asymmetry. The present findings impose constraints on computational and neural models of visual-word recognition.
doi:10.1016/j.bandl.2012.12.009
PMCID: PMC3612367  PMID: 23454070
visual-word recognition; position coding; ERPs; word-frequency; transposed-letter effects
15.  A novel method for examining response to spelling treatment 
Aphasiology  2008;22(7-8):707-717.
Background
According to a dual-route model of written language processing, spelling of irregular words provides an index of the status of lexical spelling procedures, whereas nonword spelling provides information about non-lexical processing that relies on phoneme-grapheme conversion. Because regular words can be spelled using either route, accuracy for such words may reflect the combined function of the two routes, and may be mathematically predicted on the basis of spelling accuracy for irregular words and nonwords.
Aims
The purpose of the present study was to examine the application of a dual-route prediction equation, and a related multiple regression model, to evaluate pre-post treatment spelling performance of individuals with acquired alexia/agraphia.
Methods & Procedures
Eight individuals with language impairment due to left hemisphere damage received behavioral treatment to improve their written spelling. Their spelling performance was examined before and after treatment on untrained word lists with regular and irregular spellings, and pronounceable nonwords, and concurrence between predicted and observed spelling of regular words was evaluated.
Outcomes & Results
The group demonstrated significantly improved spelling performance after treatment, and the prediction equation and multiple regression model both accurately predicted regular word performance on the basis of irregular word and nonword scores. In addition, the multiple regression model provided potentially useful information about the relative contribution of the lexical and non-lexical routes to spelling performace.
Conclusions
The prediction equation and related multiple regression model used in this study can offer novel insight into the cognitive processes available to individuals with agraphia as well as provide a quantitative means to characterize response to treatment.
doi:10.1080/02687030701800826
PMCID: PMC2706544  PMID: 19587843
Aphasia; Alexia; Agraphia; Treatment; Rehabilitation
16.  Do deep dyslexia, dysphasia and dysgraphia share a common phonological impairment? 
Neuropsychologia  2007;45(7):1553-1570.
This study directly compared four patients who, to varying degrees, showed the characteristics of deep dyslexia, dysphasia and/or dysgraphia – i.e., they made semantic errors in oral reading, repetition and/or spelling to dictation. The “primary systems” hypothesis proposes that these different conditions result from severe impairment to a common phonological system, rather than damage to task-specific mechanisms (i.e. grapheme-phoneme conversion). By this view, deep dyslexic/dysphasic patients should show overlapping deficits but previous studies have not directly compared them. All four patients in the current study showed poor phonological production across different tasks, including repetition, reading aloud and spoken picture naming, in line with the primary systems hypothesis. They also showed severe deficits in tasks that required the manipulation of phonology, such as phoneme addition and deletion. Some of the characteristics of the deep syndromes – namely lexicality and imageability effects – were typically observed in all of the tasks, regardless of whether semantic errors occurred or not, suggesting that the patients’ phonological deficits impacted on repetition, reading aloud and spelling to dictation in similar ways. Differences between the syndromes were accounted for by variation in other primary systems – particularly auditory processing. Deep dysphasic symptoms occurred when the impact of phonological input on spoken output was disrupted or reduced, either as a result of auditory/phonological impairment, or for patients with good phonological input analysis, when repetition was delayed. ‘Deep’ disorders of reading aloud, repetition and spelling can therefore be explained in terms of damage to interacting primary systems such as phonology, semantics and vision, with phonology playing a critical role.
doi:10.1016/j.neuropsychologia.2006.12.002
PMCID: PMC1894936  PMID: 17227679
deep dyslexia; deep dysphasia; deep dysgraphia; reading; repetition; spelling
17.  Letter-transposition effects are not universal: The impact of transposing letters in Hebrew 
Journal of memory and language  2009;61(3):285-302.
We examined the effects of letter transposition in Hebrew in three masked-priming experiments. Hebrew, like English has an alphabetic orthography where sequential and contiguous letter strings represent phonemes. However, being a Semitic language it has a non-concatenated morphology that is based on root derivations. Experiment 1 showed that transposed-letter (TL) root primes inhibited responses to targets derived from the non-transposed root letters, and that this inhibition was unrelated to relative root frequency. Experiment 2 replicated this result and showed that if the transposed letters of the root created a nonsense-root that had no lexical representation, then no inhibition and no facilitation were obtained. Finally, Experiment 3 demonstrated that in contrast to English, French, or Spanish, TL nonword primes did not facilitate recognition of targets, and when the root letters embedded in them consisted of a legal root morpheme, they produced inhibition. These results suggest that lexical space in alphabetic orthographies may be structured very differently in different languages if their morphological structure diverges qualitatively. In Hebrew, lexical space is organized according to root families rather than simple orthographic structure, so that all words derived from the same root are interconnected or clustered together, independent of overall orthographic similarity.
doi:10.1016/j.jml.2009.05.003
PMCID: PMC2748959  PMID: 20161017
Morphology; Letter Transposition; Hebrew; Masked-Priming
18.  The write way to spell: printing vs. typing effects on orthographic learning 
Prior research has shown superior orthographic learning resulting from spelling practice relative to repeated reading. One mechanism proposed to underlie this advantage of spelling in establishing detailed orthographic representations in memory is the motoric component of the manual movements evoked in printing or writing. This study investigated this contention directly by testing the effects of typing vs. printing on the orthographic learning achieved through spelling practice, and further evaluated whether practice modality interacts with pre-existing individual characteristics. Forty students in grade 2 (mean age 7 years 5 months) were introduced to 10 novel non-words. Some of the students practiced spelling the items by printing, while the others practiced spelling them on a keyboard. Participants were tested for recognition and spelling of these items 1 and 7 days later. Results revealed high rates of orthographic learning with no main effects of practice modality, testing time, or post-test modality. Hierarchical regression analyses revealed an interaction between typing proficiency and practice modality, such that pre-existing keyboarding skills constrained or facilitated learning within the typing-practice group. A similar interaction was not found between printing skills and learning within the printing group. Results are discussed with reference to both prominent reading theory and educational applications.
doi:10.3389/fpsyg.2014.00117
PMCID: PMC3923165  PMID: 24592247
orthographic learning; lexical representations; self-teaching; spelling; reading; literacy; printing; typing
19.  A UMLS-based spell checker for natural language processing in vaccine safety 
Background
The Institute of Medicine has identified patient safety as a key goal for health care in the United States. Detecting vaccine adverse events is an important public health activity that contributes to patient safety. Reports about adverse events following immunization (AEFI) from surveillance systems contain free-text components that can be analyzed using natural language processing. To extract Unified Medical Language System (UMLS) concepts from free text and classify AEFI reports based on concepts they contain, we first needed to clean the text by expanding abbreviations and shortcuts and correcting spelling errors. Our objective in this paper was to create a UMLS-based spelling error correction tool as a first step in the natural language processing (NLP) pipeline for AEFI reports.
Methods
We developed spell checking algorithms using open source tools. We used de-identified AEFI surveillance reports to create free-text data sets for analysis. After expansion of abbreviated clinical terms and shortcuts, we performed spelling correction in four steps: (1) error detection, (2) word list generation, (3) word list disambiguation and (4) error correction. We then measured the performance of the resulting spell checker by comparing it to manual correction.
Results
We used 12,056 words to train the spell checker and tested its performance on 8,131 words. During testing, sensitivity, specificity, and positive predictive value (PPV) for the spell checker were 74% (95% CI: 74–75), 100% (95% CI: 100–100), and 47% (95% CI: 46%–48%), respectively.
Conclusion
We created a prototype spell checker that can be used to process AEFI reports. We used the UMLS Specialist Lexicon as the primary source of dictionary terms and the WordNet lexicon as a secondary source. We used the UMLS as a domain-specific source of dictionary terms to compare potentially misspelled words in the corpus. The prototype sensitivity was comparable to currently available tools, but the specificity was much superior. The slow processing speed may be improved by trimming it down to the most useful component algorithms. Other investigators may find the methods we developed useful for cleaning text using lexicons specific to their area of interest.
doi:10.1186/1472-6947-7-3
PMCID: PMC1805499  PMID: 17295907
20.  Letters in the forest: global precedence effect disappears for letters but not for non-letters under reading-like conditions 
Normally skilled reading involves special processing strategies for letters, which are habitually funneled into an abstract letter code. On the basis of previous studies we argue that this habit leads to the preferred usage of an analytic strategy for the processing of letters, while non-letters are preferably processed via a holistic strategy. The well-known global precedence effect (GPE) seems to contradict to this assumption, since, with compound, hierarchical figures, including letter items, faster responses are observed to the global than to the local level of the figure, as well as an asymmetric interference effect from global to local level. We argue that with letters these effects depend on presentation conditions; only when they elicit the processing strategies automatized for reading, an analytic strategy for letters in contrast to non-letters is to be expected. We compared the GPE for letters and non-letters in central viewing, with the global stimulus size close to the functional visual field in whole word reading (6.5° of visual angle) and local stimuli close to the critical size for fluent reading of individual letters (0.5° of visual angle). Under these conditions, the GPE remained robust for non-letters. For letters, however, it disappeared: letters showed no overall response time advantage for the global level and symmetric congruence effects (local-to-global as well as global-to-local interference). We interpret these results as according to the view that reading is based on resident analytic visual processing strategies for letters.
doi:10.3389/fpsyg.2014.00705
PMCID: PMC4102249  PMID: 25101012
reading acquisition; global advantage effect; analytic processing; holistic processing; literacy; developmental dyslexia; congruence effect
21.  Effect of Orthographic Processes on Letter Identity and Letter-Position Encoding in Dyslexic Children 
The ability to identify letters and encode their position is a crucial step of the word recognition process. However and despite their word identification problem, the ability of dyslexic children to encode letter identity and letter-position within strings was not systematically investigated. This study aimed at filling this gap and further explored how letter identity and letter-position encoding is modulated by letter context in developmental dyslexia. For this purpose, a letter-string comparison task was administered to French dyslexic children and two chronological age (CA) and reading age (RA)-matched control groups. Children had to judge whether two successively and briefly presented four-letter strings were identical or different. Letter-position and letter identity were manipulated through the transposition (e.g., RTGM vs. RMGT) or substitution of two letters (e.g., TSHF vs. TGHD). Non-words, pseudo-words, and words were used as stimuli to investigate sub-lexical and lexical effects on letter encoding. Dyslexic children showed both substitution and transposition detection problems relative to CA-controls. A substitution advantage over transpositions was only found for words in dyslexic children whereas it extended to pseudo-words in RA-controls and to all type of items in CA-controls. Letters were better identified in the dyslexic group when belonging to orthographically familiar strings. Letter-position encoding was very impaired in dyslexic children who did not show any word context effect in contrast to CA-controls. Overall, the current findings point to a strong letter identity and letter-position encoding disorder in developmental dyslexia.
doi:10.3389/fpsyg.2012.00154
PMCID: PMC3356879  PMID: 22661961
letter-string processing; letter-position encoding; letter-identity encoding; letter transposition; letter substitution; reading acquisition; dyslexic children
22.  Do young children spell words syllabically? Evidence from learners of Brazilian Portuguese 
Journal of experimental child psychology  2013;116(4):10.1016/j.jecp.2013.08.002.
The theory that learners of alphabetic writing systems go through a period during which they treat writing as representing syllables is highly influential, especially as applied to learners of Romance languages. The results of Study 1, a 2-year longitudinal study of 76 Portuguese speakers in Brazil from 4 to 6 years of age, did not support this theory. Although most children produced some spellings of words in which the number of letters matched the number of syllables, few children produced significantly more such spellings than expected on the basis of chance. When such spellings did occur, they appeared to reflect partially successful attempts to represent phonemes rather than attempts to represent syllables. Study 2, with 68 Brazilian 4- and 5-year-olds, found similar results even when children spelled words that contained three or four syllables in which all vowels are letter names—conditions that have been thought to favor syllabic spelling. The influential theory that learners of Romance languages go through a period during which they use writing to represent the level of syllables appears to lack a solid empirical foundation.
doi:10.1016/j.jecp.2013.08.002
PMCID: PMC3854926  PMID: 24077463
Literacy development; Spelling; Prephonological spelling; Syllabic stage; Syllables; Letter names
23.  Modelling reading development through phonological decoding and self-teaching: implications for dyslexia 
The most influential theory of learning to read is based on the idea that children rely on phonological decoding skills to learn novel words. According to the self-teaching hypothesis, each successful decoding encounter with an unfamiliar word provides an opportunity to acquire word-specific orthographic information that is the foundation of skilled word recognition. Therefore, phonological decoding acts as a self-teaching mechanism or ‘built-in teacher’. However, all previous connectionist models have learned the task of reading aloud through exposure to a very large corpus of spelling–sound pairs, where an ‘external’ teacher supplies the pronunciation of all words that should be learnt. Such a supervised training regimen is highly implausible. Here, we implement and test the developmentally plausible phonological decoding self-teaching hypothesis in the context of the connectionist dual process model. In a series of simulations, we provide a proof of concept that this mechanism works. The model was able to acquire word-specific orthographic representations for more than 25 000 words even though it started with only a small number of grapheme–phoneme correspondences. We then show how visual and phoneme deficits that are present at the outset of reading development can cause dyslexia in the course of reading development.
doi:10.1098/rstb.2012.0397
PMCID: PMC3866426  PMID: 24324240
phonological decoding; developmental dyslexia; computational modelling; reading development
24.  The locus of impairment in English developmental letter position dyslexia 
Many children with reading difficulties display phonological deficits and struggle to acquire non-lexical reading skills. However, not all children with reading difficulties have these problems, such as children with selective letter position dyslexia (LPD), who make excessive migration errors (such as reading slime as “smile”). Previous research has explored three possible loci for the deficit – the phonological output buffer, the orthographic input lexicon, and the orthographic-visual analysis stage of reading. While there is compelling evidence against a phonological output buffer and orthographic input lexicon deficit account of English LPD, the evidence in support of an orthographic-visual analysis deficit is currently limited. In this multiple single-case study with three English-speaking children with developmental LPD, we aimed to both replicate and extend previous findings regarding the locus of impairment in English LPD. First, we ruled out a phonological output buffer and an orthographic input lexicon deficit by administering tasks that directly assess phonological processing and lexical guessing. We then went on to directly assess whether or not children with LPD have an orthographic-visual analysis deficit by modifying two tasks that have previously been used to localize processing at this level: a same-different decision task and a non-word reading task. The results from these tasks indicate that LPD is most likely caused by a deficit specific to the coding of letter positions at the orthographic-visual analysis stage of reading. These findings provide further evidence for the heterogeneity of dyslexia and its underlying causes.
doi:10.3389/fnhum.2014.00356
PMCID: PMC4042363  PMID: 24917802
phonological output deficit; orthographic input lexicon deficit; orthographic-visual analysis deficit; migration errors; substitution errors; developmental dyslexia
25.  The neural basis of surface dyslexia in semantic dementia 
Brain  2008;132(1):71-86.
Semantic dementia (SD) is a neurodegenerative disease characterized by atrophy of anterior temporal regions and progressive loss of semantic memory. SD patients often present with surface dyslexia, a relatively selective impairment in reading low-frequency words with exceptional or atypical spelling-to-sound correspondences. Exception words are typically ‘over-regularized’ in SD and pronounced as they are spelled (e.g. ‘sew’ is pronounced as ‘sue’). This suggests that in the absence of sufficient item-specific knowledge, exception words are read by relying mainly on subword processes for regular mapping of orthography to phonology. In this study, we investigated the functional anatomy of surface dyslexia in SD using functional magnetic resonance imaging (fMRI) and studied its relationship to structural damage with voxel-based morphometry (VBM). Five SD patients and nine healthy age-matched controls were scanned while they read regular words, exception words and pseudowords in an event-related design. Vocal responses were recorded and revealed that all patients were impaired in reading low-frequency exception words, and made frequent over-regularization errors. Consistent with prior studies, fMRI data revealed that both groups activated a similar basic network of bilateral occipital, motor and premotor regions for reading single words. VBM showed that these regions were not significantly atrophied in SD. In control subjects, a region in the left intraparietal sulcus was activated for reading pseudowords and low-frequency regular words but not exception words, suggesting a role for this area in subword mapping from orthographic to phonological representations. In SD patients only, this inferior parietal region, which was not atrophied, was also activated by reading low-frequency exception words, especially on trials where over-regularization errors occurred. These results suggest that the left intraparietal sulcus is involved in subword reading processes that are differentially recruited in SD when word-specific information is lost. This loss is likely related to degeneration of the anterior temporal lobe, which was severely atrophied in SD. Consistent with this, left mid-fusiform and superior temporal regions that showed reading-related activations in controls were not activated in SD. Taken together, these results suggest that the left inferior parietal region subserves subword orthographic-to-phonological processes that are recruited for exception word reading when retrieval of exceptional, item-specific word forms is impaired by degeneration of the anterior temporal lobe.
doi:10.1093/brain/awn300
PMCID: PMC2638692  PMID: 19022856
semantic dementia; dyslexia; parietal lobe; voxel-based morphometry; functional MRI

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