Interruption of phonological coding in conduction aphasia

A case study of conduction aphasia, investigating single word repetition, phonological coding, and short-term memory, is reported. Evidence from intact adults suggests that repetition can occur through either a lexical route or a direct auditory-articulatory link. For this conduction aphasic, E.A., the direct link was impaired, although the lexical route could be used to produce accurate single word repetition. Several experiments demonstrated a significant impairment in the generation and maintenance of an abstract phonological code. The consequences of a disruption of phonological coding on speech perception and on verbal short-term memory are discussed.     

Some aspects of phonological impairment in aphasia

The relationships between expressive and receptive phonemic disorders and between disturbances of phoneme processing and general disorders of auditory comprehension were studied in 69 aphasic patients, by means of a phoneme discrimination test and of a standard aphasia battery. A significant but incomplete correlation between disorders of phonemic output and of phoneme analysis was found. The view is put forth that in some patients only phoneme encoding or decoding is disturbed, whereas in others a central level of phoneme processing is impaired. A significant but partial correlation was also found between disorders of phonological analysis and general disorders of auditory comprehension. This supports the view that, besides sequential phonological analysis, other processes operate in auditory comprehension.     

Phoneme frequency effects in jargon aphasia: a phonological investigation of nonword errors

This study investigates the nonwords produced by a jargon speaker, LT. Despite presenting with severe neologistic jargon, LT can produce discrete responses in picture naming tasks thus allowing the properties of his jargon to be investigated. This ability was exploited in two naming tasks. The first showed that LT's nonword errors are related to their targets despite being generally unrecognizable. This relatedness appears to be a general property of his errors suggesting that they are produced by lexical rather than nonlexical means. The second naming task used a set of stimuli controlled for their phonemic content. This allowed an investigation of target phonology at the level of individual phonemes. Nonword responses maintained the English distribution of consonants and showed a significant relationship to the target phonologies. A strong influence of phoneme frequency was identified. High frequency consonants showed a pattern of frequent but indiscriminate use. Low frequency consonants were realised less often but were largely restricted to target related contexts rarely appearing as error phonology. The findings are explained within a lexical activation network with the proposal that the resting levels of phoneme nodes are frequency sensitive. Predictions for the recovery of jargon aphasia and suggestions for future investigations are made.     

The nature of the phonological disorder in conduction aphasia

Sequences of attempts to name pictured objects were used to examine phonological dysfunction in three diagnostic subgroups of aphasia. A prevalence of "phonologically-oriented sequences" (i.e., those sequences that contained only attempts with a phonological resemblance to the target word) was found to be a diagnostic criterion for conduction aphasia. When compared to a group of Broca's (n = 7) and Wernicke's (n = 5) aphasics, all the conduction aphasics (n = 6) produced proportionately more of such phonologically-oriented sequences on a picture naming test. An examination of the phonologically-oriented sequences produced by the conduction aphasics indicates that speech production in conduction aphasia involves dysfunction at an early stage of sound-encoding. The theoretical implications of this view are discussed.     

Factors predicting success in picture naming in Alzheimer's disease and primary progressive aphasia

The aim of the present study was to determine the predictive value of all important variables in the picture naming performance of 8 patients with probable Alzheimer's disease (AD) and 8 patients with primary progressive aphasia (PPA). The experimental investigation controlled for (i) visual complexity, (ii) name agreement on dominant response, (iii) age of acquisition, (iv) frequency, (v) word length, (vi) concept familiarity, and (vii) category membership. The results of the multiple regression analyses showed that age of acquisition and name agreement were significant for 10/16 subjects. Visual complexity, frequency, familiarity, and category were also significant for four patients respectively. Word length had no effect. These results are at variance with those of series of patients with AD (Gaillard et al., 1998) and with PPA (Lambon Ralph et al., 1998) where concept familiarity was found to be one of the most predictive factors of naming success.     

Sentence comprehension and working memory limitation in aphasia: a dissociation between semantic-syntactic and phonological reactivation

The relation between working memory (WM) limitation and sentence comprehension was assessed in Hebrew-speaking aphasics, three conduction aphasics and three agrammatics. The study compared sentences that required different types of reactivation-syntactic-semantic reactivation, in relative clauses, and word form/phonological reactivation, in sentences with reanalysis of lexical ambiguity. The effect of phonological memory load, manipulated by number of words intervening between the activation and the reactivation, on comprehension of the two sentence types was examined. The findings were that agrammatic aphasics failed in the comprehension of object relatives but not on subject relatives irrespective of their antecedent-gap distance. Conduction aphasics, on the other hand, who showed severe WM limitation, comprehended well all types of relative clauses and were unaffected by antecedent-gap distance. The conduction aphasics failed to understand the sentences that required phonological reactivation when the phonological distance was long. These results suggest that the type of reactivation required by the sentence, as well as the type of memory overload are crucial in determining the effect of WM limitation on sentence comprehension.     

Patterns of limb apraxia in primary progressive aphasia

Primary progressive aphasia (PPA) is a syndrome characterized by a progressive language deficit without other dementia features for at least two years (). Other deficits that are likely to co-exist with aphasia, such as apraxia, have only been investigated in a few case studies and only at a rudimentary level for the most part. In this study we investigate the frequency and severity of apraxic deficits in PPA patients. Ten PPA patients and twelve aged-matched healthy adults performed eight transitive gestures to pantomime and to imitation. Gesture performance was measured along five movement dimensions and a composite score based on the arithmetic mean of the five dimensions was calculated. Overall, PPA patients performed worse than controls with both pantomime and imitation. Furthermore, individual comparisons revealed that out of the three apraxia patterns described by (pantomime alone, imitation alone, or apraxia in both conditions), the most frequent pattern in PPA patients was apraxia in both conditions. This result corresponds with previous findings in populations of stroke and Alzheimer's patients. Considering the occurrence of apraxia in this population, this study supports the idea that a comprehensive apraxia assessment should be administered in cases of PPA.     

Category and letter fluency in semantic dementia, primary progressive aphasia, and Alzheimer's disease

This study examined the impact of various degenerative dementias on access to semantic knowledge and the status of semantic representations. Patients with semantic dementia, primary progressive aphasia, and Alzheimer's disease were compared with elderly controls on tasks of category and letter fluency, with number of words generated, mean lexical frequency and errors recorded. The findings are consistent with the view that category and letter fluency rely on both common and unique cognitive processes. Fluency tasks, with the richness of data obtained, are valuable in distinguishing different dementia syndromes from one another.     

Interaction between verbal and gestural language in progressive aphasia: a longitudinal case study.

The objective of this longitudinal study is to investigate the on-line interaction between praxis and linguistic abilities in a progressive aphasia case. During 3 years of evolution, procedural discourse of a progressive aphasic patient was videotaped five times, allowing us to analyze the progression of both language and gestural production as well as the interaction between these two. We anticipated that, in the absence of apraxia, the patient would compensate for her speech deficit by producing progressively more and more meaningful gestures. Our compensatory hypothesis was confirmed but the compensation was not as efficient as one would expect given the absence of apraxia. With the progression of the speech deficit, the patient could not replace some verbs by pantomimes that were otherwise accompanying her discourse in the preceding testing sessions. We suggest that such a compensatory ability may constitute one important characteristic of the progressive aphasia syndrome.     

Changes in brain activation induced by the training of hypothesis generation skills: an fMRI study

The aim of the present study is to investigate the learning-related changes in brain activation induced by the training of hypothesis generation skills regarding biological phenomena. Eighteen undergraduate participants were scanned twice with functional magnetic resonance imaging (fMRI) before and after training over a period of 2 months. The experimental group underwent eight biological hypothesis generation training programs, but the control group was not given any during the 2-month period. The results showed that the left frontal gyri, the cingulate gyrus, and the cuneus were activated during hypothesis generation. In addition, the brain activation of the trained group increased in the left inferior and the superior frontal gyri, which are related to working memory load and higher-order inferential processes. However, the activation after training decreased in the occipito-parietal route, which is associated with the perception and the analysis processes of visual information. Furthermore, the results have suggested that the dorsolateral prefrontal cortex (DLPFC) region is the critical area in the training of hypothesis generation skills.     

Effects of morphological complexity on phonological output deficits in fluent and nonfluent aphasia

This study examined the effects of morphological complexity on aphasic speakers with lexical-phonological output deficits. Subjects were two fluent and two nonfluent aphasic speakers who repeated morphologically simple words at the same level of accuracy and whose errors were virtually all phonological in nature. They were asked to repeat a variety of morphologically complex (i.e., affixed) words. Results were interpreted within our two-stage model of lexical-phonological production (Kohn & Smith, 1994, 1995), which we expand to include a distinction between derivational and inflectional morphology. When comparing overall performance levels between morphologically simple and complex words, only three subjects exhibited more difficulty repeating the morphologically complex targets. Nevertheless, when comparing repetition accuracy between different types of morphologically complex words (e.g., derived vs. inflected), all four subjects displayed similar patterns. These findings suggested that while morphological complexity has different effects on the two stages within the lexical-phonological output system, the relative effects of different morphological structures are constant. At the level of error analysis, patterns of affix errors distinguished the nonfluent from the fluent subjects in ways that are reminiscent of the affix errors associated with agrammatic and paragrammatic speech. This finding raised questions concerning the relationship between morphosyntactic and morphophonological deficits.     

Fluent versus nonfluent primary progressive aphasia: a comparison of clinical and functional neuroimaging features

To better characterize fluent and nonfluent variants of primary progressive aphasia (PPA). Although investigators have recognized both fluent and nonfluent patients with PPA, the clinical and neuroimaging features of these variants have not been fully defined. We present clinical and neuropsychological data on 47 PPA patients comparing the fluent (n=21) and nonfluent (n=26) subjects. We further compared language features with PET/SPECT data available on 39 of these patients. Compared to the nonfluent PPA patients, those with fluent PPA had greater impairment of confrontational naming and loss of single word comprehension. They also exhibited semantic paraphasic errors and loss of single word comprehension. Patients with nonfluent PPA were more likely to be female, were more often dysarthric, and exhibited phonological speech errors in the absence of semantic errors. No significant differences were seen with regard to left hemisphere abnormalities, suggesting that both variants result from mechanisms that overlap frontal, temporal, and parietal regions. Of the language measures, only semantic paraphasias were strongly localized, in this case to the left temporal lobe. Fluent and nonfluent forms of PPA are clinically distinguishable by letter fluency, single word comprehension, object naming, and types of paraphasic errors. Nevertheless, there is a large amount of overlap between dysfunctional anatomic regions associated with these syndromes.     

Acute pain in a clinical setting: Effects of cognitive-behavioural skills training

The present study evaluated the efficacy of cognitive-behavioural skills training, patterned after stress-inoculation training, as a preventive intervention for the attenuation of acute clinical pain during a noxious X-ray procedure—the knee arthrogram. Thirty-six adult male outpatients were randomly assigned to one of three groups: Skills Training. Attention-Placebo, and No-Treatment Control. An experimental pain test was administered before and after the interventions, as a generalization measure. Arthrogram pain was assessed by three dependent measures: patient's ratings, radiologist's ratings and videotape ratings completed by two‘blind’ raters. The results failed to support the efficacy of skills training for the attenuation of acute clinical pain, or its generalization to the experimental pain test. Although Skills Training subjects reported using significantly more coping strategies during the arthrogram. many subjects in the two control groups also reported using their own spontaneous strategies. Equivocal data were obtained on the role of ‘self-efficacy’ expectancies in mediating pain behaviour and experience. Experimental pain threshold but not pain tolerance was significantly related to acute clinical pain experienced during the arthrogram.     

The neural basis of syntactic deficits in primary progressive aphasia

Patients with primary progressive aphasia (PPA) vary considerably in terms of which brain regions are impacted, as well as in the extent to which syntactic processing is impaired. Here we review the literature on the neural basis of syntactic deficits in PPA. Structural and functional imaging studies have most consistently associated syntactic deficits with damage to left inferior frontal cortex. Posterior perisylvian regions have been implicated in some studies. Damage to the superior longitudinal fasciculus, including its arcuate component, has been linked with syntactic deficits, even after gray matter atrophy is taken into account. These findings suggest that syntactic processing depends on left frontal and posterior perisylvian regions, as well as intact connectivity between them. In contrast, anterior temporal regions, and the ventral tracts that link frontal and temporal language regions, appear to be less important for syntax, since they are damaged in many PPA patients with spared syntactic processing.     

Degree of illiteracy and phonological and metaphonological skills in unschooled adults

Phonological and metaphonological skills are explored in 97 Brazilian illiterate and semiliterate adults. A simple letter- and word-reading task was used to define the degree of illiteracy. Phonemic awareness was strongly dependent on the level of letter and word reading ability. Phonological memory was very low in illiterates and unrelated to letter knowledge. Rhyme identification was relatively preserved in illiterates and semiliterates, and unrelated to letter and word reading level. Phonetic discrimination (minimal pairs) was fairly good and marginally related to reading ability. These results suggest that phonological sensitivity, phonological memory, rhyme identification, and phonemic awareness are distinctive cognitive processes, and that only phonemic awareness is clearly and strongly dependent on the alphabetical acquisition.     

The relationship between phonological and morphological deficits in Broca's aphasia: further evidence from errors in verb inflection

A previous study of 10 patients with Broca's aphasia demonstrated that the advantage for producing the past tense of irregular over regular verbs exhibited by these patients was eliminated when the two sets of past-tense forms were matched for phonological complexity (Bird, Lambon Ralph, Seidenberg, McClelland, & Patterson, 2003). The interpretation given was that a generalised phonological impairment was central to the patients' language deficits, including their poor performance on regular past tense verbs. The current paper provides further evidence in favour of this hypothesis, on the basis of a detailed analysis of the errors produced by these same 10 patients in reading, repetition, and sentence completion for a large number of regular, irregular, and nonce verbs. The patients' predominant error types in all tasks and for all verb types were close and distant phonologically related responses. The balance between close and distant errors varied along three continua: the severity of the patient (more distant errors produced by the more severely impaired patients); the difficulty of the task (more distant errors in sentence completion>reading>repetition); the difficulty of the item (more distant errors for novel word forms than real verbs). A position analysis for these phonologically related errors revealed that vowels were most likely to be preserved and that consonant onsets and offsets were equally likely to be incorrect. Critically, the patients' errors exhibited a strong tendency to simplify the phonological form of the target. These results are consistent with the notion that the patients' relatively greater difficulty with regular past tenses reflects a phonological impairment that is sensitive to the complexity of spoken forms.