Principles of motor learning (PMLs) refer to a set of concepts which are considered to facilitate the process of motor learning. PMLs can be broadly grouped into principles based on (1) the structure of practice/treatment, and (2) the nature of feedback provided during practice/treatment. Application of PMLs is most evident in studies involving non-speech- motor tasks (e.g., limb movement). However, only a few studies have investigated the application of PMLs in speech-motor tasks. Previous studies relating to speech-motor function have highlighted two primary limitations: (1) Failure to consider whether various PMLs contribute equally to learning in both non-speech and speech-motor tasks, (2) Failure to consider whether PMLs can be effective in a clinical cohort in comparison to a healthy group. The present research was designed to shed light on whether selected PMLs can indeed facilitate learning in both non-speech and speech-motor tasks and also to examine their efficacy in a clinical group with Parkinson’s disease (PD) in comparison to a healthy group. Eighty healthy subjects with no history of sensory, cognitive, or neurological abnormalities, ranging 40-80 years of age, and 16 patients with PD, ranging 58-78 years of age, were recruited as participants for the current study. Four practice conditions and one feedback condition were considered in the training of a speech-motor task and a non-speech- motor task. The four practice conditions were (1) constant practice, (2) variable practice, (3) blocked practice, and (4) random practice. The feedback was a combination of low-frequency, knowledge of results, knowledge of performance, and delayed feedback conditions, and was paired with each of the four practice conditions. The participants in the clinical and non-clinical groups were required to practise a speech and a non-speech-motor learning task. Each participant was randomly and equally assigned to one of the four practice groups. The speech-motor task involved production of a meaningless and temporally modified phrase, and the non-speech-motor task involved practising a 12-note musical sequence using a portable piano keyboard. Each participant was seen on three consecutive days: the first two days served as the acquisition phase and the third day was the retention phase. During the acquisition phase, the participants practised 50 trials of the speech phrase and another 50 trials of the musical tune each day, and each session lasted for 60-90 min. Performance on the speech and non-speech tasks was preceded by an orthographic model of the target phrase/musical sequence displayed on a computer monitor along with an auditory model. The participants were instructed to match their performance to the target phrase/musical sequence exactly. Feedback on performance was provided after every 10th trial. The nature of practice differed among the four practice groups. The participants returned on the third day for the retention phase and produced 10 trials of the target phrase and another 10 trials of the musical sequence. Feedback was not provided during or after the retention trials. These final trials were recorded for later acoustic analyses. The analyses focused on spatial and temporal parameters of the speech and non-speech tasks. Spatial analysis involved evaluating the production accuracy of target phrase/tune by calculating the percentage of phonemes/keystrokes correct (PPC/PKC). The temporal analysis involved calculating the temporal synchrony of the participant productions (speech phrase & tune) during the retention trials with the target phrase and tune, respectively, through the phi correlation. The PPC/PKC and phi correlation values were subjected to a series of mixed model ANOVAs. In the healthy subjects, the results of the spatial learning revealed that the participants learned the speech task better than the non-speech (keyboard) task. In terms of temporal learning, there was no difference in learning between the speech and non-speech tasks. On an overall note, the participants performed better on the spatial domain, rather than on the temporal domain, indicating a spatial-temporal trade-off. Across spatial as well as temporal learning, participants in the constant practice condition learned the speech and non-speech tasks better than participants in the other practice conditions. Another interesting finding was that there was an age effect, with the younger participants demonstrating superior spatial and temporal learning to that of the older participants, except for temporal learning on the keyboard task for which there was no difference. In contrast, the PD group showed no significant differences on spatial or temporal learning between any of the four practice conditions. Furthermore, although the PD patients had poorer performances than the healthy subjects on both the speech and keyboard tasks, they showed very similar pattern of learning across all four practice conditions to that of the healthy subjects. The findings in the current study tend to have potential applications in speech-language therapy, and are as follows: (1) a constant practice regime could be beneficial in developing speech therapy protocols to treat motor-based communication disorders (e.g., dysarthria), (2) speech therapists need to exercise caution in designing speech therapy goals incorporating similar PMLs for younger and older adults, as the application of similar PMLs in younger and older adults may bring about different learning outcomes, (3) and finally, it could be beneficial for patients to practise speech tasks which would require them to focus either on the spatial or temporal aspect, rather than focussing on both the aspects simultaneously.

Acquired apraxia of speech (AOS) is a type of motor speech disorder (MSD) characterized by deficits in the motor planning or programming of speech movements (Duffy, 2005). Because AOS is often a chronic condition that may severely impair intelligibility and, thus, significantly reduce quality of life (Ballard et al., 2015), it is necessary to develop efficient and effective treatment protocols. A previous study by Youmans, Youmans, and Hancock (2011), demonstrated the efficacy of script training in the treatment of AOS. Furthermore, extensive research in general motor learning has shown that feedback is one of the most important components of motor learning (Schmidt & Lee, 2011). Research devoted specifically to speech motor learning has generally favored this view, though few studies have distinguished between the two major types of feedback: feedback providing knowledge of results (KR) and feedback providing knowledge of performance (KP). The present study is the first to examine feedback type in treatment for AOS, and the first to examine the utility of script training specifically for a participant with AOS, but no aphasia. The findings from this single-case experimental design study reveal that, compared to KR, KP resulted in greater improvements in speaking rate. KR and KP feedback resulted in comparable gains for accuracy, but condition differences were difficult to interpret due to unexpected rising baselines for the KR scripts. Both KR and KP scripts, but especially the KP scripts, outperformed the untreated control scripts, providing further support for the efficacy of script training for AOS. / Communication Sciences

Apraxia of speech (AOS) is a motor speech disorder associated with an impairment in motor planning and programming. It is therefore a logical step to derive treatment of the disorder from the principles of motor learning. Principles of motor learning refer to relatively predictable benefits of certain practice conditions over others (e.g., random practice enhances learning compared to blocked practice). A number of studies have begun to examine principles of motor learning in treatment for AOS (e.g., Austermann Hula et al., 2008; Katz et al., 2010). The current project aims to continue the investigation of motor learning principles and its application to motor speech disorders. In particular, the primary goal of this study is to examine the role of feedback control in treatment for AOS. Two types of feedback control are typically distinguished: self-controlled feedback and clinician-controlled feedback (Chiviacowsky & Wulf, 2004; Chiviacowsky & Wulf, 2007; Janelle, Barba, Frehlich, Tennant, & Cauraugh, 1997; Wulf, 2007). A secondary goal is then to examine the efficacy of script training for AOS. Youmans et al. (2011) provided promising initial evidence supporting its efficacy for AOS, yet no studies have replicated these findings (Ballard et al., 2015). The results of this study suggest that self-controlled feedback is more efficacious in treating adults with AOS than clinician-controlled feedback. Greater improvements of performance for self-controlled feedback were noted especially in accuracy of productions. There was the potential to impact rate of speech as well. Findings across conditions (treated versus untreated scripts) also indicate that script training is an efficacious method of treating adults with AOS. / Public Health

The purpose of this study was to examine how a critical principle of motor learning, practice amount (high number of trials versus a low number of trials), affects speech motor learning in childhood apraxia of speech (CAS). It also sought to contribute to the literature base regarding using an integral stimulation approach for these children. Currently, a limited evidence base exists for decision-making regarding practice amount in CAS treatment. Using a single-case experimental design with two participants, three target sets of utterances (High Amount, Low Amount, and Control) received different amounts of treatment. Outcomes were compared in terms of retention. Targets were scored regarding perceptual (prosodic and segmental) accuracy. Effect sizes were computed to quantify the extent of treatment effects. For both participants, results show some evidence suggesting a higher amount of practice is advantageous and leads to greater learning. A low amount of treatment did not show clear differences compared to not receiving any treatment. Caution should be taken when interpreting these findings due to its small sample size and modest effects. Results suggest that the integral stimulation approach may only be effective if provided with a significantly high amount of practice. Further research is needed to examine how the principles of motor learning and the integral stimulation approach should be sensibly and systematically applied to promote best outcomes for this population. / Communication Sciences

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