Malcolm R. McNeil

Defining aphasia: Some theoretical and clinical implications of operating from a formal definition

Theoretical and philosophical issues related to the need for and criteria of a formal definition of aphasia are discussed. Following a review of several definitions of aphasia and the contrast of two, a formal definition is advanced that meets the specific requirements of a scientific definition: criteria for group membership and the assumed mechanisms for these criteria. The specific criteria for group membership are discussed and the assumed mechanisms are presented. It is argued that this definition (or a well justified alternative) can serve as a first approximation to a general theory of aphasia. It is also claimed that it can inform the research consumer about important but unstated assumptions of researchers as well as provide clinical guidance.

Models of attention and dual-task performance as explanatory constructs in aphasia.

Aphasia has traditionally been viewed as a loss or impairment of language. However, evidence is presented suggesting that language mechanisms are fundamentally preserved and that aphasic language behaviors are instead due to impairments of cognitive processes supporting their construction. These processes may be understood as a linguistically specialized attentional system that is vulnerable to competition from other processing domains. We present two models of attention that focus on competition for central processing and discuss findings from dual-task studies of normal and aphasic performance. First, competing language and nonlanguage tasks appear to share limited-capacity, parallel processing resources. Second, aphasic individuals demonstrate slowed central processing that could be due to a reduction in processing capacity or ability to allocate that capacity. Third, the attention models discussed bear a coherent relationship to current models of language processing. Clinical implications of a cognitive processing account of aphasia are also considered.

Effects of speech rate on the absolute and relative timing of apraxic and conduction aphasic sentence production

The purpose of this investigation was to provide a constructive replication of the Kent and McNeil (1987, In Phonetic approaches to speech production in aphasia and related disorders. San Diego: College-Hill Press) study of the speech timing characteristics of apraxic and conduction aphasic speakers. Acoustic analysis was used to obtain absolute utterance durations, segment durations, and vowel formant trajectories from utterances produced under control, fast, and slow rate conditions. Segment-to-whole ratios and slope values were calculated. Results support the hypothesis presented by Kent and McNeil (1987) that there is a phonetic-motoric component contributing to the speech patterns of both the apraxic and conduction aphasic speakers sampled. Theories of rate control in normal and disordered speakers are discussed.

Behavioral and Pharmacological Treatment of Lexical-Semantic Deficits in a Single Patient With Primary Progressive Aphasia

In the context of a hybrid multiple-baseline design, this study demonstrated the positive effects of a behavioral + pharmacological (dextroamphetamine) treatment for lexical-semantic deficits in an...

Verbal working memory and its relationship to sentence‐level reading and listening comprehension in persons with aphasia

Background: Working memory (WM) has gained recent attention as a cognitive construct that may account for language comprehension deficits in persons with aphasia (PWA) (Caspari, Parkinson, LaPointe, & Katz, 1998; Martin, Kohen, & Kalinyak‐Fliszar, 2008; Wright, Downey, Gravier, Love, & Shapiro, 2007). However, few studies have investigated individual differences in performance on sentence comprehension tasks as a function of WM capacity in PWA when WM demands are manipulated. Aims: The purposes of the current study were: (1) to examine the relationships among verbal WM, sentence comprehension, and severity of impairment in PWA and (2) to investigate the differential performance of high versus low verbal WM groups on sentence comprehension tasks in which task demands were manipulated by the length of the sentence stimuli, complexity of syntactic structure, and by presentation method which varied the time over which the linguistic material was available for computation. Methods & Procedures: A total of 20 PWA were divided into high and low WM groups based on a listening version of a WM sentence span task. Each participant completed a listening version (CRTT) and three reading versions (CRTT‐R) of the Computerised Revised Token Test as the sentence comprehension tasks. Outcomes & Results: The WM task significantly predicted performance on the CRTT conditions in which information was only temporarily available, thereby imposing greater WM demands on sentence comprehension. The verbal WM task was significantly correlated with aphasia severity and a principal components analysis revealed that the WM task, overall aphasia severity, and overall reading impairment level loaded on a single factor with 76% of shared variance. The low WM groups performance was significantly lower than the high WM group on the CRTT subtests with syntactically more complex structures and on the CRTT conditions with temporally restricted presentation methods. Conclusions: This verbal WM task was significantly and moderately correlated with the overall severity of aphasia as well as with both listening and reading sentence comprehension. The WM group differences emerged only in sentence comprehension tasks with greater WM demands. These results are consistent with the notion that WM effects are most evident when WM capacity is sufficiently taxed by the task demands (e.g., Caplan & Waters, 1999; Just & Carpenter, 1992).

The Burden of Stroke Scale (BOSS): Validating patient-reported communication difficulty and associated psychological distress in stroke survivors

Background: The Burden of Stroke Scale (BOSS) (Doyle et al., 2002) is a health-status assessment instrument designed to measure patient-reported difficulty in multiple domains of functioning, psychological distress associated with specific functional limitations, and,general well-being in stroke survivors. Aims : This study was designed to examine the discriminative and concurrent validity of the BOSS Communication Difficulty (CD) and Communication-Associated Psychological Distress (CAPD) scales. A secondary purpose was to provide a preliminary examination of the relationships between the BOSS CD and CAPD scales and aspects of subjective well-being, including the frequency with which participants reported experiencing general positive and negative emotional states. Methods & Procedures : The BOSS was administered as a face-to-face interviewer-assisted survey to 281 medically stable, community-dwelling stroke survivors selected from five collaborating centres in the USA. Prior to administration of the BOSS, all subjects were rated for severity of communication impairment using the Boston Diagnostic Aphasia Examination (BDAE) Severity Rating Scale (Goodglass, Kaplan, & Baressi, 2001) and were administered Subtest 8 of the Revised Token Test (RTT), (McNeil & Prescott, 1978). The discriminant validity of the BOSS CD and CAPD scales was examined by comparing scores in stroke survivors with (N = 135) and without (N = 146) communication impairment, and within the communicatively impaired sample when classified according to BDAE ratings and RTT performance. Concurrent validity of the BOSS CD and CAPD scales was examined by correlating BOSS scores with BDAE ratings and RTT performance. Finally, correlations between the BOSS CAPD, BOSS CD, Positive Mood, and Negative Mood scales were calculated. Outcomes & Results : Statistical analyses revealed significant differences between communicatively impaired and non-communicatively impaired subjects on the BOSS CD and CAPD scales, as well as significant differences between communicatively impaired subjects of differing severity levels classified both by BDAE severity ratings and RTT performance. Correlational analyses revealed moderately strong relationships among the BOSS CD scale, BDAE severity ratings, and RTT performance. Finally, correlations among the BOSS CAPD, CD, Positive Mood, and Negative Mood scales revealed true covarying relationships of moderate strength between the BOSS CAPD and CD scales, and also between the CAPD and Negative Mood Scales. Conclusions : These findings provide preliminary support for the discriminant and construct validity of the BOSS Communication Difficulty (CD) and Communication Associated Distress (CAPD) Scales, and provide an empirical rationale for further research into the relationships between functional status, patient-reported health perceptions, and subjective well-being in stroke survivors with communication disorders.

Chapter 12 Motoric Characteristics of Adult Aphasic and Apraxic Speakers

Aphasia, apraxia of speech and dysarthria are the three major impairments of spoken language resulting from damage to the nervous system. Traditional definitions of these disorders imply clear separations in terms of the affected mechanisms or processes. For example, aphasia is assumed to be an impairment of language rather than a disorder of the motor control of speech. However, the contemporary classification of aphasia rests to a large degree on characteristics of speech, perhaps even on characteristics of speech motor control. This chapter examines evidence of motor disturbances in the speech patterns of certain aphasia ‘types’ and in apraxia of speech. Data from perceptual, acoustic, and physiologic investigations point strongly to the conclusion that movement-level disturbances can be observed in apraxia of speech, Broca aphasia, conduction aphasia and Wernicke aphasia. It is concluded that traditional classifications and descriptions of the aphasia syndromes and of apraxia of speech should be reconsidered in the light of recent perceptually, acoustically and physiologically derived evidence for speech movement-level deficits in speakers with these disorders.

A double-blind, placebo-controlled study of pharmacological and behavioural treatment of lexical-semantic deficits in aphasia

This investigation replicated and extended an earlier study of naming disorders (McNeil. et al. 1995) by administering a placebo and pharmacological agents (d-amphetamine and selegiline) in the presence and absence of a behavioural intervention termed lexical-semantic activation inhibition therapy (L-SAIT) to examine their effects on naming performance in two adults with stroke-induced aphasia. Results revealed acquisition and maintenance effects of L-SAIT on targeted lexical items, no effects of placebo or active pharmacological agents in the absence of L-SAIT, and no differential effects between placebo + L-SAIT and pharmacological agents + L-SAIT. Thus, positive treatment effects were attributed to L-SAIT. Generalization to untrained items within and across form class was not observed, nor was generalization to measures of informativeness of connected speech. Subject 1 evidenced improvement on the Rapid Automatized Naming Test (Denckla and Rudel 1976).

Sound production treatment for apraxia of speech: overgeneralization and maintenance effects

This investigation was designed to examine the effects of a sound production training program on the production of selected sounds from a speaker with apraxia of speech and Brocas aphasia. Treatme...

Treating apraxia of speech (AOS) with EMA-supplied visual augmented feedback

Background: Previous studies have suggested that visual augmented feedback provided by electromagnetic articulography (EMA) helps persons with apraxia of speech (AOS) recover speech motor control following stroke (e.g., Katz et al., 2007). However, the data are few, both in terms of the variety of participants and the speech motor targets investigated. Aims: This study was designed to determine whether EMA supplied feedback improves articulatory accuracy in an adult with acquired AOS. We also examined whether reduced feedback frequency results in (1) decreased performance during acquisition and (2) enhanced maintenance and generalisation of the targeted behaviours. Methods & Procedures: A multiple-baseline across-behaviours design was used to assess the efficacy of this treatment for an individual with AOS. Over a 27-week period, the participant received visual feedback provided by an EMA system for treatment of three groups of speech motor targets (SMTs): /j/, /θ/, and /t∫  / with various following VCs. The consonant clusters /br/ and /sw/ served as untreated controls. Frequency of feedback scheduling was 100% for /j/ and /t∫ /, and 50% for /θ/. Outcomes & Results: For the first group of SMTs treated, /j/, there was acquisition for 4/5 trained words. These were maintained post-treatment and at the long-term probe. Improved performance and maintenance were also noted for 5/8 untreated stimuli, with maintenance shown for most of these words by 1 month post-treatment. The next treated SMT, /θ/, showed acquisition for all five treated items. Two of these five targets were maintained one month post-treatment. All three untreated /θ/ probes showed generalisation, with two of these showing maintenance post-treatment. The third treated group of SMTs, /t∫/, showed improved performance for all of the five treated words. However, these gains could only be attributed to /t∫/ treatment for three of the five words. Two treated items appeared well maintained at 1 month post-treatment. Generalisation and maintenance were also noted for all six untreated /t∫ / words. However, generalisation from previously treated /j/ and /t∫/ targets was involved in their improved performance. The untrained (control) word data suggested that the gains noted for treated items did not result from across-the-board improvement or unassisted recovery. There were no consistent differences corresponding with low- versus high-frequency feedback conditions. Conclusions: Augmented kinematic feedback provided by an EMA system improved production for some, but not all, treated targets. Generalisation to untreated probes was also evident. Predictions concerning the effects of feedback frequency on the acquisition, maintenance, and transfer of trained behaviours were not supported.