Kirrie J. Ballard

Subtypes of progressive aphasia: application of the international consensus criteria and validation using β-amyloid imaging

Primary progressive aphasia comprises a heterogeneous group of neurodegenerative conditions with diverse clinical profiles and underlying pathological substrates. A major development has been the publication of the recent International Consensus Criteria for the three major variants namely: semantic, non-fluent/agrammatic and logopenic. The logopenic variant is assumed to represent an atypical presentation of Alzheimer pathology although evidence for this is, at present, limited. The semantic and non-fluent/agrammatic variants are largely associated with frontotemporal lobar degeneration with TDP-43 and tau pathology, respectively. The applicability of the International Consensus Criteria to an unselected clinical sample is unknown and no agreed clinical evaluation scale on which to derive the diagnosis exists. We assessed 47 consecutive cases of primary progressive aphasic seen over a 3-year period in a specialist centre, using a newly developed progressive aphasia language scale. A subgroup of 30 cases underwent (11)C-labelled Pittsburgh Compound B positron emission tomography imaging, a putative biomarker of Alzheimers disease that detects β-amyloid accumulation, and they were compared with an age-matched group (n = 10) with typical, predominately amnestic Alzheimers disease. The application of an algorithm based on four key speech and language variables (motor speech disorders, agrammatism, single-word comprehension and sentence repetition) classified 45 of 47 (96%) of patients and showed high concordance with the gold standard expert clinical diagnosis based on the International Consensus Criteria. The level of neocortical β-amyloid burden varied considerably across aphasic variants. Of 13 logopenic patients, 12 (92%) had positive β-amyloid uptake. In contrast, one of nine (11%) semantic variant and two of eight (25%) non-fluent/agrammatic cases were positive. The distribution of β-amyloid across cortical regions of interest was identical in cases with the logopenic variant to that of patients with typical Alzheimers disease although the total load was lower in the aphasic cases. Impairments of sentence repetition and sentence comprehension were positively correlated with neocortical burden of β-amyloid, whereas impaired single-word comprehension showed a negative correlation. The International Consensus Criteria can be applied to the majority of cases with primary progressive aphasic using a simple speech and language assessment scale based upon four key variables. β-amyloid imaging confirms the higher rate of Alzheimer pathology in the logopenic variant and, in turn, the low rates in the other two variants. The study offers insight into the biological basis of clinical manifestations of Alzheimers disease, which appear topographically independent of β-amyloid load.

Patterns of language decline in non-fluent primary progressive aphasia

Language samples collected yearly for up to 11 years post-onset of symptoms from four subjects presenting with non-fluent primary progressive aphasia (PPA) were analyzed and compared with samples collected from both non-brain-damaged subjects and those with agrammatic Brocas aphasia resulting from a single left-hemisphere stroke. Extensive analysis of lexical and morphosyntactic variables in these samples revealed two patterns of expressive language decline in the PPA subjects - one resembling that seen in our agrammatic aphasic subjects - i.e. impaired production of closed-class elements and loss of sentential structures governed by these elements-and the other characterized by advancing word-retrieval difficulties. These data are relevant for patient-management purposes and, in addition, they provide information relevant to language representation and organization.

Understanding the nature of apraxia of speech: Theory, analysis, and treatment

Researchers have interpreted the behaviours of individuals with acquired apraxia of speech (AOS) as impairment of linguistic phonological processing, motor control, or both. Acoustic, kinematic, and perceptual studies of speech in more recent years have led to significant advances in our understanding of the disorder and wide acceptance that it affects phonetic - motoric planning of speech. However, newly developed methods for studying nonspeech motor control are providing new insights, indicating that the motor control impairment of AOS extends beyond speech and is manifest in nonspeech movements of the oral structures. We present the most recent developments in theory and methods to examine and define the nature of AOS. Theories of the disorder are then related to existing treatment approaches and the efficacy of these approaches is examined. Directions for development of new treatments are posited. It is proposed that treatment programmes driven by a principled account of how the motor system learns to produce skilled actions will provide the most efficient and effective framework for treating motorbased speech disorders. In turn, well controlled and theoretically motivated studies of treatment efficacy promise to stimulate further development of theoretical accounts and contribute to our understanding of AOS.

Influence of order of stimulus presentation on speech motor learning: A principled approach to treatment for apraxia of speech

The present study was designed to examine whether applying principles of motor learning to a commonly used treatment approach for acquired apraxia of speech (AOS) would enhance relearning of speech production skills. In particular, we examined one main principle, random practice, and compared it to blocked practice. Of importance is the fact that many speech treatments utilize blocked practice, but the literature on motor learning clearly shows that blocked practice facilitates acquisition of target behaviours, but not retention and transfer. The latter two are considered true indices of learning. In two subjects with severe AOS, results showed that random practice facilitated retention whereas blocked practice did not. The present study provides preliminary evidence that these principles may have a similar effect on learning of skilled speech motor acts as they do on learning of limb movements. The results reported here are encouraging and provide justification and focus for further investigation.

The role of syntactic complexity in training wh-movement structures in agrammatic aphasia: optimal order for promoting generalization.

This study examined the postulate that training production of syntactically complex sentences results in generalization to less complex sentences that have processes in common with treated structures. Three agrammatic aphasic patients were trained to produce wh-movement structures, object clefts and/or object extracted who-questions, while generalization between these structures was tested. One NP-movement structure, passive sentences, also was tested for control purposes. Wh-movement occurs from the direct object position to specifier position in the complementizer phrase [SPEC, CP] for both wh-movement structures. In who-questions movement occurs in the matrix sentence, whereas, in object clefts movement occurs within an embedded relative clause, rendering them the most complex. Results showed robust generalization effects from object clefts to matrix who-question for 1 participant (D.L.); however, no generalization was noted from who-questions to object clefts for another (F.P.), and 1 participant (C.H.) showed acquisition of who-questions, but not object clefts, during the baseline condition without direct treatment. As expected, none of the participants showed improved production of passives. These findings supported those derived from our previous studies, indicating that generalization is enhanced not only when target structures are related along dimensions articulated by linguistic theory, but also when the direction of treatment is from more to less complex structures. The present findings also support proposals that projections of higher levels in the syntactic treatment are dependent on successful projection of lower levels. For our participants, training movement within CP in a lower (embedded) clause resulted in their ability to project to CP at higher levels.

Agrammatic aphasic subjects' comprehension of subject and object extracted Wh questions.

This study attempted to replicate the unusual wh question comprehension pattern of Hickok and Avrutins (1996) subjects who showed an expected subject/object extraction asymmetry for which NP questions, but not for who questions. We also examined comprehension of what and which one questions, which are similar to who and which NP questions, respectively, and we examined passivized wh questions in order to test predictions of Grodzinskys (1995) restrictive theory of trace deletion, the Trace-Based Account (TBA). Results, using both a figurine manipulation task and a picture pointing task, showed that only one of four agrammatic (Brocas) aphasic subjects showed the pattern reported by Hickok and Avrutin and that this pattern extended to comprehension of what and which one questions. One of the subjects showed subject/object asymmetry for all wh questions tested, as would be predicted by the original trace deletion hypothesis (Grodzinsky, 1984), and two subjects showed neither pattern. None of our subjects demonstrated ability to comprehend passivized wh questions as predicted by the TBA. We discuss our findings in terms of the lack of homogeneity of wh question comprehension among individuals with agrammatic aphasia and we explore alternatives to the syntactic explanation for differences between who and which NP question comprehension advanced by Hickok and Avrutin.

Paediatric speech-language pathology service delivery: an exploratory survey of Australian parents.

Abstract Consideration of client values and preferences for service delivery is integral to engaging with the evidence-based practice triangle (E3BP), but as yet such preferences are under-researched. This exploratory study canvassed paediatric speech-language pathology services around Australia through an online survey of parents and compared reported service delivery to preferences, satisfaction, and external research evidence on recommended service delivery. Respondents were 154 parents with 192 children, living across a range of Australian locations and socio-economic status areas. Children had a range of speech and language disorders. A quarter of children waited over 6 months to receive initial assessment. Reported session type, frequency, and length were incongruent with both research recommendations and parents’ wishes. Sixty per cent of parents were happy or very happy with their experiences, while 27% were unhappy. Qualitative responses revealed concerns such as; a lack of available, frequent, or local services, long waiting times, cut-off ages for eligibility, discharge processes, and an inability to afford private services. These findings challenge the profession to actively engage with E3BP including; being cognisant of evidence-based service delivery literature, keeping clients informed of service delivery policies, individualizing services, and exploring alternative service delivery methods.

Motor programming in apraxia of speech

Apraxia of Speech (AOS) is an impairment of motor programming. However, the exact nature of this deficit remains unclear. The present study examined motor programming in AOS in the context of a recent two-stage model [Klapp, S. T. (1995). Motor response programming during simple and choice reaction time: The role of practice. Journal of Experimental Psychology: Human Perception and Performance, 21, 1015-1027; Klapp, S. T. (2003). Reaction time analysis of two types of motor preparation for speech articulation: Action as a sequence of chunks. Journal of Motor Behavior, 35, 135-150] that proposes a preprogramming stage (INT) and a process that assigns serial order to multiple programs in a sequence (SEQ). The main hypothesis was that AOS involves a process-specific deficit in the INT (preprogramming) stage of processing, rather than in the on-line serial ordering (SEQ) and initiation of movement. In addition, we tested the hypothesis that AOS involves a central (i.e., modality-general) motor programming deficit. We used a reaction time paradigm that provides two dependent measures: study time (the amount of time for participants to ready a motor response; INT), and reaction time (time to initiate movement; SEQ). Two experiments were conducted to examine INT and SEQ in AOS: Experiment 1 involved finger movements, Experiment 2 involved speech movements analogous to the finger movements. Results showed longer preprogramming time for patients with AOS but normal sequencing and initiation times, relative to controls. Together, the findings are consistent with the hypothesis of a process-specific, but central (modality-independent) deficit in AOS; alternative explanations are also discussed.

Treating control of voicing in apraxia of speech with variable practice

Background: Apraxia of speech (AOS) is generally considered a phonetic‐motoric disorder. As such, it is reasonable to draw on the motor learning literature to develop interventions for improving articulation. The often cited problem of impaired voicing control is used to test the application of a variable practice approach to training skilled movements in AOS. It is predicted that variable practice—practising a behaviour over a range of possible values or contexts—increases accuracy and stability of a trained behaviour. This work was supported in part by a NIH‐NIDCD RO3 grant DC005698 to Kirrie Ballard, an American Speech Language Hearing Foundation Grant for New Investigators to Kirrie Ballard, and a San Diego State University Research Foundation Grant to Donald Robin. We thank Vanessa Doerscher for assistance with running participants, and Rebekah Abel, Valerie Flemmer, Skott Freedman, Denise Gordon, Ling‐Yu Guo, Elizabeth Lang, Michael Molley, Ydine Sandberg, and Vanessa Shaw for assistance with data analysis. Aims: The aims of the study were to test the influence of variable practice conditions on acquisition and long‐term maintenance of voiced and voiceless phonemes in words at the phrase/sentence level as well as on generalisation of treatment effects to phonemes of same and different manner. The protocol was tested on two individuals with moderate AOS, one of whom exhibited a concomitant moderate aphasia. Methods & Procedures: A single subject multiple baseline across‐subjects design was used to examine efficacy of treatment for improving control of voicing for three fricative/affricate phonemes (Participant 1) or three plosive phonemes (Participant 2). The training sets included two voiced phonemes and one voiceless phoneme, each presented in the initial position of 10 different words. This provided a range of voice onset times and a range of phonetic contexts for each target phoneme, thus providing the variable practice. The inclusion of a voiceless phoneme that was produced at a high level of accuracy during baseline was hypothesised to reduce the chance of overgeneralisation from voiced to voiceless phoneme production. Outcomes & Results: Consistent with predictions, participants demonstrated improved production of trained voiced phonemes and generalisation of treatment effects to untrained phonemes of same manner only. These effects were maintained up to 3 months post‐treatment. Results support training multiple fricatives or plosives in parallel in a variety of phonetic contexts (i.e., variable practice) as well as including a combination of voiced and voiceless phonemes in treatment to ensure maintenance of accurate voiceless phoneme production. Conclusions: Results from two participants, varying in overall communication impairment severity, provide promising evidence that a variable practice approach to retraining speech behaviours in AOS is effective. Specifically, this approach resulted in long‐term maintenance of treatment effects and generalisation of treatment effects to untrained phonemes within manner class. Just as importantly, it did not result in overgeneralisation of voicing to voiceless phonemes. Further testing is required before recommending general clinical application.

An integrative model of speech motor control: A response to Ziegler

Background : Ziegler (2003) reviews neural and behavioural evidence to support a task-dependent model of motor control, whereby motor speech disorders represent impairment of a sensory-minor system specialised for speech. Based on this approach, Ziegler argues against the examination of volitional or novel nonspeech motor activities to gain insight into motor control for speech. Aims : The primary objective of this paper is to discuss Zieglers (2003) conceptualisation of the task-dependent model and present an alternative integrative model. In the latter, speech and volitional nonspeech motor control are integrated into the functioning of a more general motor system where neural and behavioural systems demonstrate areas of overlap. Studies of the nervous system, the evolutionary foundations of speech in great apes, behaviour, and motor learning are presented to support an integrative model of motor control. Main Contribution : Neurological and evolutionary evidence strongly suggest that neural networks are flexible, multifaceted, multifunctional and overlapping in function. It is highly likely that a higher-level behaviour like speech involves networks that are similarly multifunctional and overlapping with other motor functions. Zieglers concept of task-dependent motor control may relate as much to parameters such as complexity, familiarity, and automaticity of task performance as to the nonpeech-speech distinction. Studies are reviewed that support the inclusion of nonspeech motor tasks in assessment of the disordered speech motor control system. Specific nonspeech tasks clearly facilitate differential diagnosis and provide insight into the functioning breakdown of the motor system for related but more complex speech behaviours. Finally, motor learing studies are discussed with particular reference to how these might inform models of motor control. Conclusions : This response cautions against the seemingly premature acceptance of a model assuming separate sensory motor systems for volitional nonspeech motor activities and speech. Continued research, without the limitations imposed by such an assumption, is required to enhance understanding of component parts of complex behaviours and how those components interact in normal and damaged systems at different levels of a performance. These data have the potential to form the basis for new, more effective approaches to treatment of motor speech disorders.