Is there a relation between working memory limitation and sentence comprehension? A study of conduction and agrammatic aphasia

The study explored the nature of the relation between phonological working memory and sentence comprehension in conduction and agrammatic aphasia. We compared two types of processing required during sentence comprehension: syntactic-semantic and word-form(phonological) reactivation, in 12 individuals with input-buffer conduction-aphasia(repetition), 3 with output-buffer conduction aphasia(reproduction) and 7 with agrammatism. This was done via the analysis of comprehension of relative-clauses, sentence with lexical ambiguity, and rhyming judgment. The results of the 3 experiments indicated that phonological working memory limitation only hampers comprehension when phonological reactivation is required, and the distance between the initial word and its reactivation exceeds the WM limitation

Letter Position Dyslexia

this paper two Hebrew-speaking acquired dyslexic patients with occipito-parietal lesions are presented, who suffer from a highly selective deficit to letter position encoding. As a result of this deficit, they predominantly make errors of letter migration within words (such as reading broad for board) in a wide variety of tasks: oral reading, lexical decision, same-different decision and letter location. The deficit is specific to orthographic material, and is manifested mainly in medial letter positions. The implications of the findings to models of reading and attention are discussed. In recent years several distinct types of acquired dyslexia have been identified. These discoveries owe much to a fruitful interaction between the study of reading disorders and information processing models. The models of normal single word reading have been constructed and shaped by the identification of selective deficits, each indicative of failures in different parts and stages of the reading process (e.g., Coltheart, 1981; Patterson, 1981). On the other hand, new dyslexic patterns have been identified following predictions derived from information processing models and other, already known, types of dyslexia have become better understood through their use. Most of the components of these word-reading models have been found to have correlates in selective reading deficits. The later stages of reading, such as the orthographic lexicon, the grapheme to phoneme converter, and the connections between them, have been found to be selectively impaired in various central dyslexias (Shallice & Warrington, 1980). We thank Uri Hadar, David Swinney, and Karalyn Patterson for their helpful comments and discussions. Address correspondence to Naama Friedmann, School ..

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Letter form as a constraint for errors i

Letter position dyslexia

Many word-reading models assume that the early stages of reading involve a separate process of letter position encoding. However, neuropsychological evidence for the existence and selectivity of this function has been rather indirect, coming mainly from position preservation in migrations between words in attentional dyslexia, and from nonselective reading deficits. No pure demonstration of selective impairment of letter position function has yet been made. In this paper two Hebrew-speaking acquired dyslexic patients with occipito-parietal lesions are presented who suffer from a highly selective deficit to letter position encoding. As a result of this deficit, they predominantly make errors of letter migration within words (such as reading “broad ” for “board”) in a wide variety of tasks: oral reading, lexical decision, same-different decision, and letter location. The deficit is specific to orthographic material, and is manifested mainly in medial letter positions. The implications of the findings to models of reading and attention are discussed

Letter Form as a Constraint for Errors in Neglect Dyslexia and Letter Position Dyslexia

Does letter-form constrain errors in peripheral dyslexia? In Hebrew, 5 of the 22 letters have two different letter forms, one is used only when the letter occurs in word-final position, the other form is used in initial and middle positions. Is the information on final-forms encoded in the letter identity information and used for word identification, or is it discarded? The current research explored this question through the effect of final vs. non final letter form on the error pattern in neglect dyslexia (neglexia) and letter position dyslexia (LPD). Left word-based neglexia results in errors of omission, substitution and addition of letters in the left side of words, which in Hebrew is the end of the word. We examined whether final letter form blocks the addition of letters to the end of the word and whether omissions of letters after letters in non-final form are avoided. The predominant error type in LPD is migration of letters within words. We tested whether migrations also occur when they cause form change of either final-form letters that move to middle position or middle-form letters that move to final position. These questions were assessed in both acquired and developmental neglexia and LPD. The results indicated a strong effect of final letter-form on acquired neglexia and on acquired and developmental LPD, which almost completely prevented form-changing errors. This effect was not found in developmental neglexia, where words that end in final-form letters were actually more impaired than other words, probably because final-form letters appear only on the neglected side of the word for Hebrew-reading children with left developmental neglexia. These data show that early visuo-orthographic analysis is sensitive to final letter form and that final letter form constrains errors in peripheral dyslexia