Are the same phoneme and lexical layers used in speech production and comprehension? A case-series test of model of aphasic speech production

In this paper, we investigate the claim that although the same lexical units are involved in speech production and comprehension, there are separate input and output phoneme layers (Foygel and Dell, 2000). Data from a case series of aphasic patients are used to test this claim by examining the relationship between performance on a test of picture naming and performance on tests of phonological input. Estimates of each patient's semantic-lexical and phonological impairments in speech production were derived from Foygel and Dell's computational model of picture naming. It was found that the strength of the semantic-lexical impairments in speech production was significantly correlated with performance on auditory comprehension tests. This finding is consistent with the claim that the same lexical units are involved in speech comprehension and production. Conversely, the correlations between the strength of the phonological lesions in speech production and performance on tests of phonological input were non-significant, consistent with Foygel and Dell's claim that there are distinct input and output phoneme layers.     

Slow event-related brain activity of aphasic patients and controls in word comprehension and rhyming tasks

Slow event-related potentials (ERP) were examined in healthy and aphasic subjects in two-stimulus designs comprising a word comprehension and a rhyming task. Aphasics, though selected to perform above chance level, made significantly more errors and responded more slowly than controls, although canonical correlations did not indicate a statistical relationship between performance measures and ERP amplitudes. A discriminant analysis of ERP amplitudes distinguished the groups for the slow wave (SW; 0.5-1.0 s post-S1 onset) in the word comprehension, for the SW and the initial contingent negative variation (iCNV; 1.0-2.0 s post-S1 onset) in the rhyming task. Similarly for both tasks, ERP topography showed left-anterior predominance of the negative SW and iCNV in controls, whereas participants with aphasia showed smaller anterior and larger left-posterior amplitudes. The centroparietal terminal CNV (tCNV; 1 s pre-S2) was smaller in participants with aphasia than in controls, but similar in topography. Results suggest left-anterior activation for those language processes that were presumably provoked in the present tasks, like lexical access, or phonological encoding. The pattern of participants with aphasia may indicate effects of language impairment and recovery, but also consequences of the brain damage.     

Processes of phonological change in developmental speech disorders

Two analytical frameworks for identifying and measuring the processes of phonological change in the speech of children with developmental speech disorders are described. The frameworks are illustrated by an examination and evaluation of longitudinal data from children with this type of disorder. The ways in which clinicians can use the two frameworks to guide treatment planning are discussed     

Dissociation between exact and approximate addition in developmental dyslexia

Previous research has suggested that number sense and language are involved in number representation and calculation, in which number sense supports approximate arithmetic, and language permits exact enumeration and calculation. Meanwhile, individuals with dyslexia have a core deficit in phonological processing. Based on these findings, we thus hypothesized that children with dyslexia may exhibit exact calculation impairment while doing mental arithmetic. The reaction time and accuracy while doing exact and approximate addition with symbolic Arabic digits and non-symbolic visual arrays of dots were compared between typically developing children and children with dyslexia. Reaction time analyses did not reveal any differences across two groups of children, the accuracies, interestingly, revealed a distinction of approximation and exact addition across two groups of children. Specifically, two groups of children had no differences in approximation. Children with dyslexia, however, had significantly lower accuracy in exact addition in both symbolic and non-symbolic tasks than that of typically developing children. Moreover, linguistic performances were selectively associated with exact calculation across individuals. These results suggested that children with dyslexia have a mental arithmetic deficit specifically in the realm of exact calculation, while their approximation ability is relatively intact.     

Semantic and phonological fluency in children with Down syndrome: Atypical organization of language or less efficient retrieval strategies?

In this study the verbal fluency procedure was used to investigate the organization of semantic and phonological representations in children with Down syndrome (DS) and typically developing children, matched pairwise for receptive vocabulary age. Productivity was found to be significantly reduced in the DS group in both the semantic and the phonological tasks. However, group differences in the number of clusters as opposed to cluster size suggest that this may reflect less efficient retrieval strategies rather than differences in the organization of linguistic representations. Together the findings point to executive deficits in Down syndrome rather than deviant language processes.     

Input and output modes modulate phonological and semantic contributions to immediate serial recall: Evidence from a brain-damaged patient

Psycholinguistic models of short-term retention suggest that performance at verbal short-term memory (STM) tasks relies on the activation of phonological, lexical, and semantic representations, the relative impact of each depending on task variables. This was tested in normal individuals and in I.R., a brain-damaged patient with a phonological deficit. In Experiment 1, the effect of phonological and semantic similarity was assessed under different presentation formats (words, pictures) and recall modes (oral, picture pointing, and picture pointing among distractors). In Experiment 2, effects were compared using reproduction and reconstruction responses. When words were used at input, controls showed robust phonological similarity effects irrespective of response mode. In contrast, I.R. showed a reliable semantic effect. However, both studies indicated that when response mode promoted order recuperation (reconstruction and picture pointing modes), I.R. showed a typical phonological similarity effect with no semantic contribution. The data support current psycholinguistic views suggesting that the short-term retention of verbal items depends on the temporary activation of word representations. In healthy controls, presentation mode appears to modulate the role of those representations but in I.R., it was the output condition—particularly whether order was or was not required—that was found to be crucial with respect to the appearance of semantic or phonological effects. This supports the important role that order information plays in short-term memory tasks.     

Do reading processes differ in transparent versus opaque orthographies? A study of acquired dyslexia in Welsh/English bilinguals

In English, the relationship between the written and spoken forms of words is relatively opaque, leading to proposals that skilled reading requires two procedures: (a) a sublexical grapheme/phoneme conversion process allowing the correct reading of regular words (CAT) and new or pseudowords (ZAT); (b) a lexical process necessary to read irregular words accurately (TWO) and assumed to be the dominant process for familiar words. However, it has been argued that the sublexical process may be sufficient in highly transparent languages such as Welsh. If this is the case, damage to the sublexical process may lead to more severe deficits in transparent languages due to the lack of an alternative lexical process. To test this hypothesis, we compared Welsh and English oral reading and written-word recognition and comprehension in seven bilingual stroke participants with comparably impaired pseudoword reading in English and Welsh. Performance was remarkably similar across languages. Irrespective of the language tested, words were read more accurately than pseudowords. Lexical decision and word comprehension were as accurate in Welsh and in English, and when imageability effects were present they were of a similar size in both languages. This study does not support the hypothesis that orthographic transparency determines the nature of cognitive reading processes, but rather suggests that readers develop a sight vocabulary through reading experience irrespective of orthographic transparency.     

工作记忆与发展性阅读障碍

发展性阅读障碍是学习障碍的一种类型。研究发现,发展性阅读障碍者常常在工作记忆任务中表现出缺陷。根据Baddeley的工作记忆模型,这些研究一般是围绕语音环、视-空画板以及中央执行器这三个方面来进行的,涵盖了行为和脑神经机制两个层面。近年来,一些研究者开始针对发展性阅读障碍进行工作记忆训练,这方面的研究也取得了一些成果。这些研究成果为揭示汉语发展性阅读障碍的内在机制以及开发相应的训练矫正程序提供了借鉴。     

Do phonological neighbourhood density and phonotactic probability influence speech output accuracy in acquired speech impairment?

Background: Among the many factors that may affect speech production, phonological neighbourhood density (ND) and phonotactic probability (PROB) have displayed effects on speech and language performance in healthy speakers. It is not clear if they show an effect in impaired speech output after stroke and if they do whether this is facilitatory or inhibitory.

Aims: To determine whether ND and/or PROB play a role in speech production accuracy in acquired output impairment after stroke.

Methods & Procedures: A total of 20 English native speakers with acquired spoken output impairment after stroke repeated 906 single-word stimuli. They included real and nonsense words varying in syllable structure, length, and complexity, as well as syllable and word frequency, ND, and PROB. Responses were transcribed phonetically and scored as either correct or incorrect. Logistic regression analyses were completed for each speaker separately to determine the effects of ND and PROB on repetition accuracy in relation to controlled variables.

Outcomes & Results: A total of 14 speakers showed a positive effect of PROB on repetition accuracy. Only two individuals displayed a positive effect of ND. No double dissociations regarding the effect of ND and PROB were noted.

Conclusions: ND does not appear to have a significant independent effect on repetition accuracy in speakers with acquired output impairment after stroke. By contrast PROB has a positive effect on repetition accuracy in impaired speakers, but does not appear to be a major determinant of output accuracy. Results are discussed in relation to study design and future work to further examine issues around ND and PROB and their possible role in clinical differential diagnosis of output disorders.