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PubMed2006

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.

Aged↗
PubMed2005

Letter processing in the visual system: different activation patterns for single letters and strings.

One would expect that a lifetime of experience recognizing letters would have an important influence on the visual system. Surprisingly, there is limited evidence of a specific neural response to letters over visual control stimuli. We measured brain activation during a sequential matching task using isolated characters (Roman letters, digits, and Chinese characters) and strings of characters. We localized the visual word form area (VWFA) by contrasting the response to pseudowords against that for letter strings, but this region did not show any other sign of visual specialization for letters. In addition, a left fusiform area posterior to the VWFA was selective for letter strings, whereas a more anterior left fusiform region showed selectivity for single letters. The results of different analyses using both large regions of interest and inspections of individual patterns of response reveal a dissociation between selectivity for letter strings and selectivity for single letters. The results suggest that reading experience fine-tunes visual representations at different levels of processing. An important conclusion is that the processing of nonpronounceable letter strings cannot be assumed to be equivalent to single-letter perception.

Adult↗
PubMed2004

What do letter migration errors reveal about letter position coding in visual word recognition?

Dividing attention across multiple words occasionally results in misidentifications whereby letters apparently migrate between words. Previous studies have found that letter migrations preserve within-word letter position, which has been interpreted as support for position-specific letter coding. To investigate this issue, the authors used word pairs like STEP and SOAP, in which a letter in 1 word could migrate to an adjacent letter in another word to form an illusory word (STOP). Three experiments show that both same-position and adjacent-position letter migrations can occur, as well as migrations that cross 2 letter positions. These results argue against position-specific letter coding schemes used in many computational models of reading, and they provide support for coding schemes based on relative rather than absolute letter position.

Adolescent↗
PubMed1995

Electrophysiological indicants of black-white discrimination performance for letter and non-letter patterns.

This study examined event-related potentials (ERPs) and behavioral measures, considered to be sensitive to the selective processing of black versus white letter and non-letter patterns, in a group of seventy-four randomly selected 6 to 8 year old children. Results demonstrated faster and more accurate behavioral performance on the experimental task for the letter than for the non-letter patterns. The ERP measures provided complementary information regarding this letter facilitation effect, indicating that the selective neural processing of letter as compared to non-letter patterns was present in the electrophysiological waveform within the initial 100-140 ms after stimulus presentation. Later ERP measures (200-260 and 500-600 ms post-stimulus) in response to the letter stimuli showed greater differences as a function of task relevance over the left than over the right hemisphere. The results from the present study indicate a remarkably early facilitative influence of stimulus type (letter versus non-letter patterns) on the luminance discrimination of these stimuli and are consistent with an overlap of linguistic and perceptual processing.

Automatism↗
PubMed1985

[Effects of noise letters upon selective identification of letters].

Eighteen undergraduate students participated in two experiments which were designed to investigate the effects of noise letters upon selective identification of target letters. The reaction time of pressing buttons to the target letter was measured under various combinations of accompanying noise letters located 1 degree 48' apart from a target in visual angle, and added noise letters inserted between the target and accompanying noise letters. The results provided evidence in favor of the hypothesis which attributes the interfering effects of noise letters not to the processing level, but to the response level. Moreover, the results suggested that the noise letter adjacent to a target plays an important part in this interference, though the noise letters can be processed even in the position as much as 1 degree 48' apart from a target, and that it is especially important what relations the adjacent noise letter has with the response of the target.

Adolescent↗
PubMed1990

Cross-modality word matching in letter-by-letter readers.

Letter-by-letter readers can match spoken words to printed words they cannot read. Good word-matching ability may be attributable to a priming effect. However, since letter-by-letter readers have intact spelling ability, an alternative hypothesis is that word matching depends on a strategy of scanning printed words for recognizable letters known to be in the target items. In the present study, experimental manipulations that taxed the ability of the two subjects to process key letters (those that distinguished target words from foils) or scan for them caused a decline in word-matching performance. Thus, letter-by-letter readers may rely on sequential letter processing to accomplish cross-modality word matching.

Aged↗
PubMed1982

Differential effects of concurrent letters on visual field differences in letter recognition.

To examine whether concurrently presenting surrounding scripts affect single Alphabet recognition, subjects compared letters which appeared in the left or the right visual field to a previously presented sample letter. Four different comparison stimuli were prepared, target letter embedded in same-type print letters, in different-type letters, in different kinds of characters, and in blank space (control). The results indicated that both RTs for letter matches and visual field differences were different depending upon the kind of letters that surrounded the target Alphabet. This finding strongly suggests that letter recognition is affected by the presence of neighbouring letters, and further that the nature of the surroundings can differentially affect cerebral hemispheric functioning.

Attention↗
PubMed1996

The quality and relationship of referral and reply letters. The effect of introducing a pro forma letter.

OBJECTIVE: An intervention study was conducted to assess the effect of a pro forma letter on the quality of referral letters from general practitioners at a rural hospital in KwaZulu-Natal, and on the quality and rate of replies received. METHOD: 254 referral letters and 111 replies were evaluated. RESULTS: The quality of referral letters improved after the introduction of the pro forma letter, but the quality of replies did not. The reply rate (43.5%) did not change, and the quality of replies showed a low correlation with the quality of referral letters, indicating that improvements in the quality of referral letters will not necessarily bring about improvements in the quality of replies. Instead, the reply rate was found to be influenced mainly by the hospital to which the patient was referred. Replies were also observed to function poorly as a means of continuing medical education. CONCLUSION: Pro forma letters improve the quality of referral letters, but on their own do not improve the rate and quality of replies. Personal contact between referring doctors and consultants would seem to be an important factor in respect of the latter.

Communication↗
PubMed2005

How to make the word-length effect disappear in letter-by-letter dyslexia: implications for an account of the disorder.

The diagnosis of letter-by-letter (LBL) dyslexia is based on the observation of a substantial and monotonic increase of word naming latencies as the number of letters in the stimulus increases. This pattern of performance is typically interpreted as indicating that word recognition in LBL dyslexia depends on the sequential identification of individual letters. We show, in 7 LBL patients, that the word-length effect can be eliminated if words of different lengths are matched on the sum of the confusability (visual similarity between a letter and the remainder of the alphabet) of their constituent letters. Additional experiments demonstrate that this result is mediated by parallel letter processing and not by any compensatory serial processing strategy. These findings indicate that parallel processing contributes significantly to explicit word recognition in LBL dyslexia and that a letter-processing impairment is fundamental in causing the disorder.

Dyslexia, Acquired↗
PubMed2006

Alphabetic skills in preschool: a preliminary study of letter naming and letter writing.

Development of letter naming and writing (skills in writing first name, dictated and copied letters, and dictated and copied numbers) was examined in 79 preschool children (M age = 56 months). Skills were assessed in the fall to determine the status of these procedural skills that are components of alphabetic knowledge at the start of the school year. Children with high letter-naming scores also had high scores on letter writing, including dictated or copied letters and writing some or all of the letters of their names. Letter-naming skills were related to number-writing skills whether the numbers were dictated or copied. The highest writing scores were found for first name writing compared to writing or copying letters and numbers. A focus on the development of procedural knowledge in the preschool period may yield the hopep for impacts on later reading skills that has not been found in curricula emphasizing conceptual knowledge (e.g., knowledge of print concepts, book conventions).

Child↗
PubMed1999

The role of letter identity and letter position in orthographic priming.

Four experiments are reported investigating orthographic priming effects in French by varying the number and the position of letters shared by prime and target stimuli. Using both standard masked priming and the novel incremental priming technique (Jacobs, Grainger, & Ferrand, 1995), it is shown that net priming effects are affected not only by the number of letters shared by prime and target stimuli but also by the number of letters in the prime not present in the target. Several null results are thus explained as a tradeoff between the facilitation generated by common letters and the inhibition generated by different letters. Inhibition was significantly reduced when different letters were replaced by nonalphabetic symbols. Facilitation effects disappeared when the common letters did not have the same relative position in the prime and target strings, thus supporting a relative-position coding scheme for letters in words.

Adult↗
PubMedDate not supplied

Dissociation of reading strategies: letter-by-letter reading in the native language and normal reading in the learned language. A case study.

In letter-by-letter reading, which is typically observed in Dejerine's (1892) "pure alexia," oral reading seems to be mediated by the naming of the constituent letters of the printed sequence: reading time rises abnormally as a function of the number of letters of the target item. We describe a patient with fluent aphasia who showed the unusual pattern of letter-by-letter reading together with surface dyslexia in her native language (French) and apparently normal reading in the second, learned language (English). Thus, letter-by-letter reading should be considered as a description of a symptom rather than the consequence of a unique type of functional impairment.

Brain Injuries↗
PubMed1995

Altered visual field asymmetries for letter naming and letter matching as a result of concurrent presentation of threatening and nonthreatening words.

Thirty-two right-handed subjects (16 male and 16 female students) were administered a unilateral letter-naming task and two unilateral letter-matching tasks: physical-identity letter matching (shape task) and nominal-identity letter matching (name task). Each task contained three conditions. In control conditions, no concurrent task was given. In threat and nonthreat conditions, each unilateral stimulus was preceded by a centrally presented threatening or nonthreatening word. Subjects were instructed to recall this word after their response to the lateral stimulus. With letter naming, each trial consisted of three consonants presented horizontally to the left or right visual field. Across conditions, subjects identified more letters correctly in the right visual field than in the left visual field. The concurrent presentation of threatening words resulted in a selective enhancement of left visual-field performance. In the control condition of the shape task, same letter pairs were identified faster than different pairs when they were presented to the right visual field. The concurrent presentation of threatening words resulted in a selective shortening of left visual-field latencies to same pairs. In the name task, the concurrent presentation of threatening words resulted in improved accuracy on left visual field trials. No sex differences in perceptual asymmetries and in emotional priming effects were found. The results demonstrate that threatening stimuli can activate the right hemisphere and alter the laterality patterns for several tasks.

Affect↗
PubMed1995

Facilitation and interference in indirect/implicit memory tests and in the process dissociation paradigm: the letter insertion and the letter deletion tasks.

This paper introduced the letter insertion and letter deletion tasks. In these tasks participants are presented with letter strings and are instructed to insert or delete a letter to create a word. Experiment 1 demonstrated facilitation priming and established these tasks as sensitive indirect measures of memory. Experiments 2 and 3 demonstrated interference priming effects. In Experiment 4 the process dissociation paradigm (Jacoby, 1991) was applied to investigate the contributions of automatic and consciously controlled processes to performance on the letter insertion task. In addition, performance in the exclusion condition demonstrated an interference effect caused by automatic retrieval. Potential applications for the letter insertion and letter deletion tasks are discussed.

Adult↗
PubMed1989

Word recognition and orthographic context effects in a letter-by-letter reader.

The performance of letter-by-letter readers when attempting to decipher written material gives the impression that words fail to directly evoke any higher-level representation. As a consequence, spelling patterns appear to be treated perceptually as if they were a collection of random letters. We tested the hypothesis that words are no longer mapped onto orthographic descriptions by examining the ability of a letter-by-letter reader to identify letters in familiar words, pseudowords, and random strings. A clear effect of orthographic context was obtained on the accuracy of letter recognition, indicating that spelling patterns do gain access to more central components of the reading mechanism. The implications of this result for our understanding of the syndrome are discussed.

Attention↗
PubMed1992

Alphabetic sequence decisions for letter pairs with separations of one to three letters.

The alphabet storage and retrieval theory of Klahr, Chase, and Lovelace (1983) was tested for applicability to letter-order decisions. Ss judged whether letter pairs with sequential separations of 1, 2, or 3 letters were in correct or incorrect order. Ss made decisions either in a continuous- or intermittent-attention mode. The results for alphabetic letter-order decisions with a letter separation of 1 were in conformance with the theory of Klahr et al. in both attention modes. However, at letter separations of 2 and 3 letters, Ss made decisions that were more compatible with a symbolic-distance mechanism. Speculation on how Ss could make alphabetic-order decisions in either a memory-consultation or a symbolic-distance manner is made.

Adult↗
PubMed1987

Letter recognition at low contrast levels: effects of letter size.

Contrast variation was used to measure recognition thresholds for lowercase letters, with the aim of obtaining a better understanding of the role that early stages of visual processing play in letter recognition. Frequency-of-recognition curves were measured for alphabets of different letter size. Since variation of the adaptational state of the eye changes the characteristics of primary visual processing in a quantifiable way, recognition thresholds were measured both at a high (150 cd m-2) and at a low (0.9 cd m-2) adaptation level. Thresholds decreased as letter size increased, in a way comparable with data on visual acuity. At the lower adaptation level, recognition thresholds became higher, which is also in accordance with visual acuity data. Furthermore, the slopes of the frequency-of-recognition curves for alphabets as a function of log contrast decreased with decreasing letter size. It is argued that this is mainly caused by an increasing dispersion of internal representations of individual letters on the internal psychological scale as letter size decreases.

Adaptation, Ocular↗
PubMed2004

Improving the quality of outpatient clinic letters using the Sheffield Assessment Instrument for Letters (SAIL).

AIM: To improve the quality of outpatient letters used as communication between hospital and primary care doctors. METHODS: On 2 separate occasions, 15 unselected outpatient letters written by each of 7 hospital practitioners were rated by another hospital doctor and a general practitioner (GP) using the Sheffield Assessment Instrument for Letters (SAIL). Individualised feedback was provided to participants following the rating of the first set of letters. The audit cycle was completed 3 months later without forewarning by repeat assessment by the same hospital and GP assessors using the SAIL tool to see if there was any improvement in correspondence. SETTING: Single centre: general paediatric outpatient department in a large district general hospital. RESULTS: All 7 doctors available for reassessment completed the audit loop, each providing 15 outpatient letters per assessment. The mean of the quality scores, derived for each letter from the summation of a 20-point checklist and a global score, improved from 23.3 (95% CI 22.1-24.4) to 26.6 (95% CI 25.8-27.4) (P = 0.001). CONCLUSIONS: The SAIL provides a feasible and reliable method of assessing the quality and content of outpatient clinic letters. This study demonstrates that it can also provide feedback with a powerful educational impact. This approach holds real potential for appraisal and revalidation, providing an effective means for the quality improvement required by clinical governance.

Communication↗