Does phonological working memory impairment affect sentence comprehension? A study of conduction aphasia

Background: The nature of the relation between phonological working memory and sentence comprehension is still an open question. This question has theoretical implications with respect to the existence of various working memory resources and their involvement in sentence processing. It also bears clinical implications for the language impairment of patients with phonological working memory limitation, such as individuals with conduction aphasia.

Aims: This study explored whether limited phonological working memory impairs sentence comprehension in conduction aphasia.

Methods & Procedures: The participants were 12 Hebrew-speaking individuals with conduction aphasia who, according to 10 recall and recognition span tasks, had limited phonological short-term memory in comparison to 296 control participants. Experiments 1 and 2 tested their comprehension of relative clauses, which require semantic-syntactic reactivation, using sentence–picture matching and plausibility judgement tasks. Experiments 3 and 4 tested phonological reactivation, using two tasks: a paraphrasing task for sentences containing an ambiguous word in which disambiguation requires re-accessing the word form of the ambiguous word, and rhyme judgement within sentences. In each task the distance between a word and its reactivation was manipulated by adding words/syllables, intervening arguments, or intervening embeddings.

Outcomes & Results: Although their phonological short-term memory, and hence their phonological working memory, was very impaired, the individuals with conduction aphasia comprehended relative clauses well, even in sentences with a long distance between the antecedent and the gap. They failed to understand sentences that required phonological reactivation when the phonological distance was long.

Conclusions: The theoretical implication of this study is that phonological working memory is not involved when only semantic-syntactic reactivation is required. Phonological working memory does support comprehension in very specific conditions: when phonological reactivation is required after a long phonological distance. The clinical implication of these results is that because most of the sentences in daily language input can be understood without phonological reactivation, individuals with phonological working memory impairment, such as individuals with conduction aphasia, are expected to understand sentences well, as long as they understand the meaning of the sentences and do not attempt to repeat them or encode them phonologically.     

As far as individuals with conduction aphasia understood these sentences were ungrammatical: Garden path in conduction aphasia

Background: Recent studies have indicated that working memory is not a unitary resource and that different types of working memory are used for different types of linguistic processing: syntactic, semantic, and phonological. Phonological working memory was found to support the comprehension of sentences that require re‐access to the word‐form of a word that appeared earlier in the sentence.

Aims: This study explored the relation between phonological working memory and sentence comprehension by testing the comprehension of garden path sentences in individuals with conduction aphasia who have very limited phonological working memory. Our prediction was that if phonological working memory limitation hampers word‐form reactivation, only the comprehension of garden paths that require word‐form reactivation will be impaired, whereas garden paths that require only structural reanalysis will be better preserved.

Methods & Procedures: Five individuals with conduction aphasia and 15 matched controls participated in working memory tests and a garden path comprehension test. The phonological working memory assessment included a battery of 10 tests, which showed that four of the individuals, who had input conduction aphasia, had very limited phonological working memory, and one individual, with output conduction aphasia, had unimpaired working memory. The comprehension study included 60 garden path sentences of three types: structural garden paths, which require only structural reanalysis, lexical garden paths, which require lexical re‐access in addition to structural reanalysis, and optional‐complement garden paths, which require re‐access to the lexical‐syntactic frame of the verb in addition to the structural reanalysis.

Outcomes & Results: The main result was that the individuals with input conduction aphasia showed different degrees of impairment in different types of garden path sentences. The lexical garden paths were exceptionally hard for them, with a mere 10% correct, and significantly more difficult than the structural garden paths. The individual with output conduction aphasia whose working memory was intact comprehended the lexical garden paths similarly to the normal controls.

Conclusions: These findings indicate that phonological working memory impairment only affects the comprehension of sentences that require phonological, word‐form re‐access. The type of sentence and the type of processing it requires should be taken into account when trying to predict the effect of working memory limitation on a patient's ability to understand sentences. Whereas individuals with input conduction aphasia can understand complex syntactic structures well, they have considerable difficulties understanding sentences that also require re‐access to a word‐form.     

Long-term maintenance of novel vocabulary in persons with chronic aphasia

Background: The study of novel word learning in aphasia can shed light on the functionality of patients' learning mechanisms and potentially help in treatment planning. Previous studies have indicated that persons with aphasia are able to learn some new vocabulary. However, these learning outcomes appear short-lived and evidence for the ability to use the newly learned words in the long term is lacking.

Aims: Participants with aphasia and matched controls underwent short training where they were taught to name novel objects with novel names. We studied the participants' word learning and particularly their long-term maintenance. We also examined whether the language and verbal short-term memory impairments of the participants with aphasia related to their ability to acquire and maintain phonological and semantic information on novel words.

Methods & Procedures: Two participants with nonfluent aphasia, LL and AR, and two matched controls took part in the experiment. They were taught to name 20 unfamiliar objects by repeating the names in the presence of the object picture. Half of the items carried a definition that was used to probe incidental semantic learning. There were four training sessions, a post-training test, and follow-up tests up to 6 months post-training. Learning measures included recognition of the trained objects, as well as spontaneous and cued recall in visual confrontation naming. Incidental semantic learning was measured by spontaneous recall of the definitions.

Outcomes & Results: Combining spontaneous and phonologically cued responses, LL acquired 70% and AR 55% of the novel words. With phonological cueing, LL named 50% of the items correctly up to 6 months post-training (vs 95–100% for the controls) and AR 25% up to 8 weeks post-training. AR's lexical-semantic processing, pseudoword repetition and verbal short-term capacity were inferior to those of LL. In line with this, AR learned fewer words and showed more decline in recognition memory for the trained items, and weaker recall of the semantic definitions.

Conclusions: Our results support previous findings that people with aphasia can learn to name novel items. More importantly, the results show for the first time that, with phonological cueing, an individual with aphasia can maintain some of this learning up to 6 months post-training. Moreover the results provide further evidence for the significance of the functional status of lexical-semantic processing on word learning success.     

Phonological short-term memory in conduction aphasia

Background: Within cognitive neuropsychological models conduction aphasia has been conceptualised as a phonological buffer deficit. It may affect the output buffer, the input buffer, or both. The phonological output buffer is a short-term storage, responsible for the short-term maintenance of phonological units until their articulation, as well as for phonological and morphological composition. The phonological input buffer holds input strings until they are identified in the input lexicon. Thus the phonological buffers are closely related to phonological short-term memory (pSTM), and hence it is important to assess pSTM in conduction aphasia. Because the input and output buffers play different roles, impairment in each of them predicts different impairments in the patient's ability to understand certain sentences, to learn new words and names, and to remember and recall lists of words and numbers for short time periods.

Aims: This study explored in detail pSTM in individuals with conduction aphasia, comparing individuals with input and output deficits, recall and recognition tasks, and stimuli of various types. It also tested pSTM in six age groups of healthy individuals, assessing the effect of age on various types of stimuli. This paper presents a new battery of 10 recall and recognition span tests, designed to assess pSTM in aphasia and to measure spans and effects on spans.

Methods & Procedures: The participants were 14 Hebrew-speaking individuals with conduction aphasia, 12 with input or input-output phonological buffer deficit, and 2 with only output deficit, and 296 healthy individuals.

Outcomes & Results: The analyses of the spans and effects on pSTM in the 10 tests indicated that all the participants with conduction aphasia had limited pSTM, significantly poorer than that of the control participants, and no semantic STM impairment. They had shorter spans, smaller length and similarity effects, and larger sentential effect than the controls. The individuals with conduction aphasia who had an impairment in the phonological input buffer showed deficit in both the recall and recognition span tasks. The individuals with the output conduction aphasia showed impairment only in the recall tasks. The healthy individuals showed age effect on span tasks involving words, but no effect of age on span tasks of nonwords.

Conclusions: pSTM is impaired in conduction aphasia, and different pSTM impairments characterise different types of conduction aphasia. Output conduction aphasia causes difficulties only when verbal output is required, whereas input conduction aphasia also causes a deficit when only recognition is required. This suggests that rehearsal can take place without the phonological output buffer. Age differentially affects pSTM for words and nonwords in healthy adults: whereas the encoding of words changes, the ability to remember nonwords is unchanged.     

Executive dysfunction in patients with spinocerebellar ataxia type 3

The aim of this study was to assess the cognitive functions of patients with spinocerebellar ataxia type 3(SCA3). We examined 15 patients with genetically confirmed SCA3 and 15 healthy control subjects matched for age, years of education, and intellectual ability. We administered verbal memory (word recall and word recognition) and executive function tasks (word fluency test, forward and backward digit and visual span tests, Kana Pick-out Test, Trail Making Test, and conflicting instructions and a Go/NoGo task from the Frontal Assessment Battery). We found that patients with SCA3 had significantly lower scores than the healthy control subjects on the word recall, semantic, and letter fluency, and backward digit span tests, while word recognition was well preserved. The other executive function tests showed preserved functions in the SCA3 group, indicating that visual working memory, and attention and inhibition control were not affected. The patients with SCA3 showed impaired word recall and intact word recognition, and accordingly, episodic memory encoding and storage processes in short-term memory were preserved. In category and letter-fluency tests, impairment was attributable to word-retrieval from semantic memory. Impaired verbal working memory may be involved in the retrieval of verbal information from phonological storage by means of continuous subvocal rehearsal, rather than a deficit in initial phonological encoding. Essential executive dysfunction in patients with SCA3 may be due to damage in the cerebellar cortex–ventral dentate nucleus–thalamus–prefrontal cortex circuits, which are involved in strategic retrieval of verbal information from different modes of memory storage.     

Effects of syntactic and semantic argument structure on sentence repetition in agrammatism: Things we can learn from particles and prepositions

Background: Sentence production impairment in aphasia has been attributed to several possible sources that are not mutually exclusive. Linguistic accounts often attribute the difficulty to the complexity of a verb's syntactic and/or semantic argument structure. Cognitive processing accounts emphasise the reduced processing capacity observed in agrammatic aphasia, which in turn has been attributed to reduced semantic short-term memory (STM) or slowed processing.

Aims: In this study we used verb particles and prepositions to investigate effects of differences in syntactic and semantic argument structure on sentence repetition in aphasia. We predicted that verb particles and sentences containing verb-particle constructions would be easier to repeat than prepositions and prepositional transitive sentences, as the former have a less-complex semantic and syntactic argument structure than the latter. Also, semantic and phonological spans were assessed to determine if a reduction in either capacity correlates with repetition ability.

Methods & Procedures: Participants were eight individuals with chronic aphasia. The experimental task was repetition of transitive sentences balanced for length and lexical content containing either verb particles or prepositional object structures. Accuracy of sentence repetition and repetition of verb particles and prepositions within sentences was examined. We calculated the effect of structural complexity on the sentence repetition task as the difference between proportion correct of verb-particle constructions and prepositional transitives. Semantic and phonological STM spans and word spans were also assessed and correlated with this measure of the structural complexity effect on sentence repetition.

Outcomes & Results: Verb-particle sentences were repeated correctly significantly more often than prepositional transitive sentences, and within those sentences verbal particles were repeated correctly significantly more often than prepositions. The effect was strongly associated with fluency scores: it was present in participants with low fluency scores, but not in those with high fluency scores. The phonological, but not the semantic, STM probe span measure correlated with both the difference in accurate repetition of verb-particle and prepositional transitive sentences and the particles and prepositions within those sentences.

Conclusions: Results indicate that differences in argument structure of particle and preposition constructions influence sentence repetition in agrammatic aphasia. The finding that lower fluency scores are associated with poorer performance on more complex structures suggests that this effect is associated with agrammatism. The impact of these structural distinctions between particles and prepositions should be taken into account during development of treatment stimuli for those with agrammatism.     

Semantic and phonological loop effects on verbal working memory in middle-age adults with mental retardation

Semantic and phonological loop effects on verbal working memory were examined among middle-age adults with Down syndrome and those with unspecified mental retardation in the context of Baddeley's working memory model. Recall was poorer for phonologically similar, semantically similar, and long words compared to recall of dissimilar short words. Compared to their peers, participants with Down syndrome had poorer recall in all categories except phonologically similar words. Most interestingly, semantic similarity lowered recall scores only in participants with Down syndrome. This selective effect of semantics reflects an influence of long-term memory on working memory and points to the need for additional explanations outside phonological loop processes to completely account for the relative impairment of verbal working memory among individuals with Down syndrome.     

More evidence for a continuum between phonological and deep dyslexia: Novel data from three measures of direct orthography-to-phonology translation

Background: Over recent years a number of studies have suggested that phonological and deep dyslexia are not separate acquired dyslexias but actually reflect different points along a single continuum. Behaviourally this continuum was originally defined in terms of the graded presence/absence of the “symptoms” of deep dyslexia.

Aims: Given that orthography → phonology translation is core to phonological-deep dyslexia, it becomes critical to measure the degree and nature of any such direct phonological activation in these patients. Nonword reading accuracy has been the most commonly used measure of the status of direct orthographic → phonological activation but this measure can floor out in many phonological-deep dyslexic patients. In such circumstances, however, researchers have found evidence for some residual O→P function using reading tasks that do not require overt production—and these tasks might provide an important set of additional measures to test for a gradation of performance at the severer end of the phonological-deep dyslexic continuum.

Methods & Procedures: In the present study three tasks of this type (spoken-to-written nonword-matching, a novel word-matching task, and pseudohomophone reading) were developed and tested in a case-series of phonological-deep dyslexia (and made available in the appendices to this paper).

Outcomes & Results: As suggested from past studies, even patients with severely impaired overt nonword reading exhibited above-chance performance on the matching task and a pseudohomophone effect. The accuracy on these tasks varied in a graded manner across the case-series.

Conclusions: Two factors are key to this dyslexia continuum: the severity of phonological impairment and also the degree of interaction between semantic and impaired phonological representations, indicating that semantic representations become more central to reading in the face of phonological impairment.     

Dissociating short-term memory and language impairment: The importance of item and serial order information

Background: Selective verbal short-term memory (STM) deficits are rare, and when they appear, they are often associated with a history of aphasia, raising doubts about the selectivity of these deficits. Recent models of STM consider that STM for item information depends on activation of the language system, and hence item STM deficits should be associated with language impairment. By contrast, STM for order information is considered to recruit a specific system, distinct from the language system: this system could be impaired in patients with language-independent STM deficits.

Aims: We demonstrate here the power of the item–order distinction to separate STM and language impairments in two brain-damaged cases with STM impairment and a history of aphasia.

Methods & Procedures: Recognition and recall STM tasks, maximising STM for either item or order information were administered to patients MB and CG.

Outcomes & Results: Patient MB showed mild phonological impairment. As predicted, associated STM deficits were characterised by poor item STM but preserved order STM. On the other hand, patient CG showed no residual language deficits. His STM deficit was characterised by poor order STM but perfectly preserved item STM.

Conclusions: This study presents the first double dissociation between item and order STM deficits, and demonstrates the necessity of this distinction for understanding and assessing STM impairment in patients with and without aphasia.     

How does linguistic knowledge contribute to short-term memory? Contrasting effects of impaired semantic knowledge and executive control

Background: Linguistic knowledge makes an important contribution to verbal STM. Some theories, including Baddeley's original conception of the episodic buffer, hold that harnessing linguistic knowledge to support STM is executively demanding. However, some recent evidence suggests that the linguistic contribution does not depend on executive resources.

Aims: In this study we tested the hypothesis that activation of language representations is automatic and that executive control is most important when the material to be remembered is incompatible with this automatic activation.

Methods & Procedures: Word list recall was tested in three patients with transcortical sensory aphasia (TSA) following stroke. All had preserved word repetition and digit span but poor comprehension associated with impaired executive control. They were compared with two semantic dementia (SD) patients with degraded semantic representations but intact executive control. Patients repeated word lists that varied in their semantic and syntactic resemblance to meaningful sentences.

Outcomes & Results: The executively impaired TSA patients showed large benefits of semantic and syntactic structure, indicating that their executive deficits did not interfere with the normal linguistic contribution to STM. Instead they showed severe deficits in repetition of scrambled word lists that did not follow usual syntactic rules. On these, the patients changed the word order to better fit their existing knowledge of syntactic structure. In contrast, the SD patients had no problems repeating words in unusual sequences but their semantic knowledge degradation led to frequent phonological errors due to a loss of “semantic binding”, the process by which semantic knowledge of words helps to constrain their phonological representation.

Conclusions: These findings suggest that linguistic support for STM consists of (a) automatic activation of semantic and syntactic knowledge and (b) executive processes that inhibit this activation when it is incompatible with the material to be remembered.     

Effects of working memory load on processing of sounds and meanings of words in aphasia

BACKGROUND: Language performance in aphasia can vary depending on several variables such as stimulus characteristics and task demands. This study focuses on the degree of verbal working memory (WM) load inherent in the language task and how this variable affects language performance by individuals with aphasia. AIMS: The first aim was to identify the effects of increased verbal WM load on the performance of judgments of semantic similarity (synonymy) and phonological similarity (rhyming). The second aim was to determine if any of the following abilities could modulate the verbal WM load effect: semantic or phonological access, semantic or phonological short-term memory (STM) and any of the following executive processing abilities: inhibition, verbal WM updating, and set shifting. METHOD AND PROCEDURES: Thirty-one individuals with aphasia and 11 controls participated in this study. They were administered a synonymy judgment task and a rhyming judgment task under high and low verbal WM load conditions that were compared to each other. In a second set of analyses, multiple regression was used to identify which factors (as noted above) modulated the verbal WM load effect. OUTCOME AND RESULTS: For participants with aphasia, increased verbal WM load significantly reduced accuracy of performance on synonymy and rhyming judgments. Better performance in the low verbal WM load conditions was evident even after correcting for chance. The synonymy task included concrete and abstract word triplets. When these were examined separately, the verbal WM load effect was significant for the abstract words, but not the concrete words. The same pattern was observed in the performance of the control participants. Additionally, the second set of analyses revealed that semantic STM and one executive function, inhibition ability, emerged as the strongest predictors of the verbal WM load effect in these judgment tasks for individuals with aphasia. CONCLUSIONS: The results of this study have important implications for diagnosis and treatment of aphasia. As the roles of verbal STM capacity, executive functions and verbal WM load in language processing are better understood, measurements of these variables can be incorporated into our diagnostic protocols. Moreover, if cognitive abilities such as STM and executive functions support language processing and their impairment adversely affects language function, treating them directly in the context of language tasks should translate into improved language function.     

Improved verbal learning in the semantic variant of primary progressive aphasia when using semantic cues

The semantic variant of primary progressive aphasia (PPA-S) is characterized by impairments in confrontation naming and single word comprehension. Although episodic memory may be relatively spared, there can be impairment in verbal learning tasks. We report a patient with PPA-S and impaired verbal learning who was tested to learn if when provided with semantic categories, her learning would improve. A 70-year-old right-handed woman with a 2-year history of progressive difficulties with word finding, naming, and memory was tested for language and memory deficits using the Hopkins Verbal Learning Test-Revised (HVLT-R). She was then retested with the HVLT-R after being provided with the three semantic categories to which these words belonged. Confrontation naming was impaired on the Boston Naming Test. Sentence repetition was normal. Comprehension testing with word picture matching and sentence comprehension was normal. On a test of semantic associations, Pyramids and Palm Trees, she was impaired. She was also impaired on tests of verbal learning (HVLT-R) (total: 13) but not recall. When a different version of the HVLT-R was given with the semantic categories of the words given beforehand, her scores improved (total: 26). This patient with PPA-S had an impairment of verbal learning, but not delayed recall. When given a semantic category cue beforehand, her verbal learning performance improved. This observation suggests that this patient did not spontaneously use semantic encoding. Using a semantic cueing strategy may help other patients with PPA-S improve their capacity for verbal learning.     

Verbal short‐term memory in Down's syndrome: An articulatory loop deficit?

Background Verbal short‐term memory, as measured by digit or word span, is generally impaired in individuals with Down's syndrome (DS) compared to mental age‐matched controls. Moving from the working memory model, the present authors investigated the hypothesis that impairment in some of the articulatory loop sub‐components is at the base of the deficient maintenance and recall of phonological representations in individuals with DS. Methods Two experiments were carried out in a group of adolescents with DS and in typically developing children matched for mental age. In the first experiment, the authors explored the reliance of these subjects on the subvocal rehearsal mechanism during a word‐span task and the effects produced by varying the frequency of occurrence of the words on the extension of the word span. In the second experiment, they investigated the functioning of the phonological store component of the articulatory loop in more detail. Results A reduced verbal span in DS was confirmed. Neither individuals with DS nor controls engaged in spontaneous subvocal rehearsal. Moreover, the data provide little support for defective functioning of the phonological store in DS. Conclusions No evidence was found suggesting that a dysfunction of the articulatory loop and lexical‐semantic competence significantly contributed to verbal span reduction in subjects with DS. Alternative explanations of defective verbal short‐term memory in DS, such as a central executive system impairment, must be considered.     

Effects of semantic context on access to words of low imageability in deep-phonological dysphasia: a treatment case study

Background: Deep dysphasia is a relatively rare subcategory of aphasia, characterised by word repetition impairment and a profound auditory-verbal short-term memory (STM) limitation. Repetition of words is better than nonwords (lexicality effect) and better for high-image than low-image words (imageability effect). Another related language impairment profile is phonological dysphasia, which includes all of the characteristics of deep dysphasia except for the occurrence of semantic errors in single word repetition. The overlap in symptoms of deep and phonological dysphasia has led to the hypothesis that they share the same root cause, impaired maintenance of activated representation of words, but that they differ in severity of that impairment, with deep dysphasia being more severe.

Aims: We report a single-subject multiple baseline, multiple probe treatment study of a person who presented with a pattern of repetition that was consistent with the continuum of deep-phonological dysphasia: imageability and lexicality effects in repetition of single and multiple words and semantic errors in repetition of multiple-word utterances. The aim of this treatment study was to improve access to and repetition of low-imageability words by embedding them in modifier-noun phrases that enhanced their imageability.

Methods & Procedures: The treatment involved repetition of abstract noun pairs. We created modifier-abstract noun phrases that increased the semantic and syntactic cohesiveness of the words in the pair. For example, the phrases “long distance” and “social exclusion” were developed to improve repetition of the abstract pair “distance-exclusion”. The goal of this manipulation was to increase the probability of accessing lexical and semantic representations of abstract words in repetition by enriching their semantic -syntactic context. We predicted that this increase in accessibility would be maintained when the words were repeated as pairs, but without the contextual phrase.

Outcomes & Results: Treatment outcomes indicated that increasing the semantic and syntactic cohesiveness of low-imageability and low-frequency words later improved this participant’s ability to repeat those words when presented in isolation.

Conclusions: This treatment approach to improving access to abstract word pairs for repetition was successful for our participant with phonological dysphasia. The approach exemplifies the potential value in manipulating linguistic characteristics of stimuli in ways that improve access between phonological and lexical-semantic levels of representation. Additionally, this study demonstrates how principles of a cognitive model of word processing can be used to guide treatment of word processing impairments in aphasia.     

Semantic contributions to immediate serial recall: Evidence from two contrasting aphasic individuals

This paper examines the effect of semantic variables on serial recall in two contrasting aphasic cases and a group of controls. Experiment 1 manipulates word imageability and Experiment 2 manipulates semantic similarity. Controls not only showed better recall of imageable/semantically grouped lists, but under some conditions they also produced proportionately fewer phonological errors. These findings suggest that increasing the effectiveness of lexical/semantic support reduces reliance on phonological support. Consistent with this proposal, case TV, whose phonological impairment should increase his reliance on lexical/semantic support, produced abnormally low rates of phonological errors under some conditions. Conversely, case NP, who had a lexical/semantic impairment, produced abnormally high rates of phonological errors under some conditions. Analysis of serial recall curves in both aphasics and controls support the hypothesis that phonological processes are particularly critical for the recall of list-final items. However, there was no evidence that semantic support is especially crucial for list-initial recall. Controls did not exhibit stronger effects of semantic variables at list-initial position. Case NP (lexical/semantic impairment) performed disproportionately poorly on these items, but only under certain conditions.     

The impact of phonological or semantic impairment on delayed auditory repetition: Evidence from stroke aphasia and semantic dementia

Background/Aims: This study aimed to evaluate the interactive account of repetition by examining the influence of factors that differentially tapped semantic and phonological processing in a case series of patients with semantic or phonological impairment. Methods & Procedures: We compared two patient groups: predominantly phonologically impaired cases with aphasia following cerebrovascular accident, and patients with semantic dementia. Immediate repetition was contrasted with repetition after a 5-second filled delay, and lexicality, frequency, and imageability were manipulated—therefore both the task and the neuropsychological impairment biased processing in favour of either lexical-semantic or phonological capacities. Outcomes & Results: Substantial interactivity was observed between phonological/semantic impairment and variables largely tapping these processes. The phonologically impaired patients showed substantial effects of lexicality and imageability that were larger in delayed than immediate repetition. The semantically impaired patients exhibited the complementary pattern, showing reduced effects of these lexical-semantic variables and a delay effect that was larger for more poorly comprehended, low-frequency items. Semantic errors were related to phonological deficits whereas semantic impairment led to an increase in phonological errors. The phonologically impaired stroke cases also made more perseverative responses. Conclusions: These findings support the view that repetition is underpinned by interaction between semantics and phonology within a single route and not by distinct lexical and sub-lexical pathways. The results also provide evidence of a continuum between phonological and deep dysphasia.     

Phonological working memory in children with phonological impairment

Phonological working memory was examined in a group of children with phonological impairment and a group of normal age-matched controls. Based on the Baddeley and Hitch model of working memory, traditional serial recall tasks of word length and phonological similarity were used to examine the efficiency of subvocal rehearsal and short-term storage, respectively. Analysis of recall performance for lists of four and six words revealed that, in comparison to agematched controls, children with phonological impairment are similarly sensitive to the effects of word length and phonological similarity, but demonstrate poorer overall recall for word lists of unrelated items. Theoretically, these findings suggest that the subvocal rehearsal mechanism and the phonological short-term store appear to be operating efficiently in this group of children with phonological impairment. Therefore their poorer recall performance may be attributable to interactions between short-term memory processes and aspects of phonological knowledge stored in long-term memory rather than to specific components of a phonological loop.     

Naming Concepts: Evidence of Two Routes

This study examines a parallel distributed processing (PDP) model (partly based on the Wernicke-Lichtheim information processing model) that posits two routes for naming concepts, whole word and phonological. To test the two naming route hypothesis of this model, we performed confrontation naming tests that were either uncued, semantically cued, or phonologically cued in a patient with naming impairment due to Broca’s aphasia. In spoken language and in uncued naming to confrontation, word retrieval was severely impaired and marked by semantic but no phonemic paraphasic errors. With semantic cues, naming behavior was unchanged; however, with phonological cues, naming success was enhanced but frequent phonemic paraphasias were produced. These results suggest that the patient spontaneously engaged the whole word naming route, but when given phonological cues, he engaged an alternative phonological naming route that incorporated phonological sequence knowledge.     

Case Study Impairment to phonological processes in a Cantonese‐speaking brain‐damaged patient

Background: Previous studies have shown that brain‐damaged patients with selective deficits to phonological processes produced frequent phonological errors and similar error patterns in all spoken tasks, exhibited the effects of word frequency, grammatical class, and imageability, and were unable to make rhyming judgements, due to impaired lexical retrieval and/or phonological representations. Aims: This paper describes a Cantonese‐speaking brain‐damaged patient, LKK, whose performance patterns in spoken tasks indicate impairment to both the lexically mediated non‐semantic and semantic pathways of oral production, as well as the phonological output buffer. Methods & Procedures: A range of tasks was conducted including repetition, reading aloud, oral naming, written/spoken word–picture matching, non‐verbal semantic tests, written lexical decision, and homophone judgements. Outcomes & Results: LKK performed normally on written lexical decision, word–picture matching, and non‐verbal semantic tests, but he was unable to make homophone judgements and showed impaired production in all oral tasks. He was better able to read aloud names of objects than to name them. He also made more semantic errors in naming than reading. His accuracy in reading single words was affected by word frequency and form class. Further observations of his oral production included better (but nevertheless impaired) performance on repetition than reading and naming, a consistent effect of word length across tasks, and a tendency for phonological errors to occur on the coda compared with the onset. Conclusions: There was sufficient evidence for deficits of the phonological lexicon and/or the access to it along the non‐semantic route and the semantic pathway at the post‐semantic level in LKK. The effect of word length and comparable patterns of error distribution across spoken tasks suggested additional impairment to the phonological output buffer. The different levels of accuracy in repetition, reading, and naming, as well as the differential rates of semantic errors in these tasks were consistent with predictions of the summation hypothesis.