Dopamine (DA) is a modulatory neurotransmitter required for movement, learning, and reward. Several neuropsychiatric disorders exhibit DAergic dysfunction, including Parkinson’s disease (PD). The presynaptic DA transporter (DAT) constrains DAergic signaling via DA reuptake. Acute PKC activation drives DAT endocytosis, however, endogenous receptor-mediated DAT trafficking in striatal terminals remains ill-defined. Here, I present data supporting biphasic Gq-receptor-mediated DAT trafficking in striatum. Gq-receptor activation drives initial DAT insertion, which requires DA release, DAergic DRD2auto activation, and intact retromer. Subsequent DAT retrieval requires PKC and the neuronal GTPase Rit2. Furthermore, I demonstrate that the endogenous Gq-coupled metabotropic glutamate receptor, mGluR5, expressed on DAergic neurons exerts biphasic DAT regulation. DAergic mGluR5 silencing revealed that mGluR5 is required for motor learning and coordination. DAergic mGluR5 cKO motor deficits were rescued by DAT inhibition, suggesting mGluR5-mediated DAT trafficking is required for these behaviors. Apart from its requisite role in DAT trafficking, Rit2 is a PD associated risk allele. We previously demonstrated that Rit2 is required for psychostimulant response and generalized anxiety, but not basal locomotion. However, Rit2’s roles in more complex motor behaviors and PD pathology remain unknown. DAergic Rit2 silencing revealed that Rit2 is required for male motor learning and prolonged Rit2 suppression leads to progressive manifestation of PD biomarkers, coordination deficits, and decreased DAergic tone. Motor learning deficits were rescued by boosting DA availability, echoing Rit2-mediated hypodopaminergia. Together these results identify receptor-mediated DAT trafficking mechanisms in DA terminals, demonstrate that DAT surface dynamics are required for motor function, and implicate DAergic Rit2 loss in progressive PD-like phenotypes.

Background: Due to the deficit of knowledge on fine motor skill far transfer from one domain of expertise to another, piano performance and surgical training serve as a relevant, interdisciplinary context in which to study the transfer of motor skills given both have relatively well-established levels of performance and require complex fine motor skills. Musicians tend to demonstrate greater ease in all aspects of procedural knowledge which are known to contribute to the early stages of motor learning. Previous research in the Piano Pedagogy Research Laboratory (PPRL) found that extensive piano training was correlated with faster learning of surgical knot-tying skills. However, the short-term two-day timeline was a limitation of the study. Objective: Our project has built on previous work in the PPRL to address the short-term nature of previous studies by measuring a long-term performance curve as well as retention of surgical training and also expanded on the previous project by focussing this time on laparoscopic tasks. This study compared performance curves of two participant groups (pianists and controls) over five consecutive days and retention one week later, as measured by speed and accuracy of task completion. Laparoscopic training consisted of six tasks repeated at every session. Since laparoscopy involves a variety of abilities concurrently, we also administered a battery of ten psychometric tests to isolate and measure specific aspects of non-motor and fine motor skills. Results: There was no statistical difference between participant groups on the majority of laparoscopic training and psychomotor assessments based on two-way mixed ANOVA and Mann-Whitney U test analysis, respectively. There were also little to no significant correlations between abilities and laparoscopic performance. The only significant confounding variable was that the control group was significantly more interested in surgery than the musician group (p = .037). Conclusion: Overall, these results demonstrate that piano performance training did not far transfer to laparoscopic surgery. This is relevant to the debate on far transfer of motor skills given this study’s robust design which addressed previous shortcomings by including a longer timeline and more specifications of musicians’ characteristics. Our findings indicate that fine motor skills are domain specific to music and surgery, respectively.

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Social-comparative feedback (i.e., providing a learner with information regarding his/her performance relative to a group average) has been shown to influence a learner’s psychological and behavioural outcomes during motor skill acquisition (Avila, Chiviacowsky, Wulf, & Lewthwaite, 2012; Eliasz, 2012; Lewthwaite & Wulf, 2010; McKay, Lewthwaite, & Wulf, 2012; Stoate, Wulf, & Lewthwaite, 2012; Wulf, Chiviacowsky, & Cardozo, 2014; Wulf, Chiviacowsky, & Lewthwaite, 2010, 2012; Wulf & Lewthwaite, 2016). This research indicates that motor skill acquisition is facilitated when learners believe they are performing better than the average, regardless of their actual performance. It has been suggested (Wulf & Lewthwaite, 2016) that a better-than-average mindset enhances psychological factors such as self-efficacy and motivation and in turn, actual behaviour. However, there is also evidence to suggest that self-efficacy (having state-like properties) and motivation (having both state and trait-like properties) are related in terms of their affective influence on learning (Bandura, 1997; Schunk, 1990, 1991, 1995) but the relationship between the two constructs and its subsequent outcomes remain unclear. Even though individual differences in motivation have been suggested to influence self-efficacy beliefs, they have been largely ignored in this line of research. There is also evidence to suggest that learners possessing high levels of motivation (whether that may be at a trait or state level) may not interpret feedback in the same manner (Aronson, 1992; Festinger, 1957; Frey, 1986; Harmon-Jones, 2012; Harmon-Jones & Harmon-Jones, 2002; Harmon-Jones, Harmon-Jones, Fearn, Sigelman, & Johnson, 2008; Harmon-Jones & Mills, 1999; Harmon-Jones, Schmeichel, Inzlicht, & Harmon- Jones, 2011; Steele, 1988). Therefore, the goal of this dissertation is use both theoretical and applied perspectives to examine the degree to which social- comparative feedback affects psychological and behavioural outcomes in highly- motivated learners (e.g., medical trainees) learning procedural skills. Independent of actual performance, we provided manipulated feedback information to novice pre-clerkship medical trainees while they were learning motor skills to suggest that they were performing better or worse than the average. The first study used a basic sequential key-press learning task (Eliasz, 2012) and a basic suturing task to explore the role of social-comparative feedback in medical trainees and tested whether features of the task were important (i.e., basic laboratory task or technical skill task) during the interpretation of this feedback. The second study used the same experimental paradigm to extend our results to a relevant medical education context (i.e., medical trainees learning basic suturing techniques). The final study examined whether the credibility of the feedback provider (i.e., expert versus peer) played a role in how social-comparative feedback was being internalized by novice medical trainees. Our initial study demonstrated that, compared to those receiving positive or no social-comparative feedback, medical trainees receiving negative social- comparative feedback during motor skill acquisition had significant difficulties in learning both the laboratory and technical skill task. These findings suggested that compared to other learners, novice medical trainees (a subset of highly-motivated learners), responded differently to social-comparative feedback. The second study replicated this pattern and revealed that medical trainees receiving below-average feedback during technical skill acquisition experienced significant detriments to their performance, learning and self-efficacy. Our final study found that regardless of the feedback source (hypothetical expert versus another peer), the experience of receiving negative social-comparative feedback impacted self- reported psychological measures and the immediate performance of a basic surgical technique. This dissertation provides, to the best of our knowledge, the first demonstration that medical trainees, a subset of highly-motivated learners, interpret social-comparative feedback differently than other learners studied in the literature. More specifically, receiving positive social-comparative feedback did not facilitate the learning process as found in previous studies with non-medical learners, while the delivery of negative social-comparative feedback, irrespective of task or feedback provider, was psychologically and behaviourally detrimental to novice medical trainees learning motor skills. / Dissertation / Doctor of Philosophy (PhD) / This dissertation includes three original studies designed to examine the effects of social-comparative feedback during skill acquisition in highly- motivated learners (e.g., medical trainees). Regardless of actual task performance, novice medical trainees who were provided with feedback during the learning process indicating that they were performing worse than the group average, experienced significant detriments to their psychological and behavioural outcomes. This effect was present regardless of the task being learned (i.e., key- pressing or suturing) or who was delivering the feedback (i.e., a hypothetical ‘expert’ or ‘peer’). Receiving better-than-average feedback did not result in any additional psychological and behavioural benefits. Contrary to the research with non-medical students, where “you are above-average” social-comparative feedback facilitates learning and “you are below-average” social-comparative feedback is no different than a control condition, these studies suggest that the experience of receiving below-average feedback during the learning process can be detrimental for highly-motivated novice learners. These findings are important to consider in both the context of feedback delivery and remediation as they provide evidence that novice medical trainees, regardless of the task and feedback provider, experience difficulty in receiving information that they are performing relatively poorly compared to their peers.

Within the last decade, the influence of focus of attention (FOA) instruction on postural control has been an increased interest among researchers (Yeh et al., 2016; McNevin et al., 2013). The general agreement when it comes to the role of FOA has been that adopting an external (EXT) FOA enhances the efficiency of motor programming by strengthening the relationship between movement planning and outcome, when compared to an internal (INT) FOA (see Wulf, 2013). However, increasing evidence suggests that the benefits from an EXT FOA can be mitigated by certain factors (e.g., age, skill level, novelty of the task and task complexity; Becker & Smith, 2013; Emanuel et al., 2008). As such, questions remain as to what form of FOA instruction is best suited for young learners, as FOA research has been criticized for being studied almost exclusively among adults (Agar et al., 2016). Research in this area is particularly sparse as it pertains to FOA in combination with postural control among this younger age group. This is particularly problematic as significant changes in postural control, stability and balance occur during one’s first decade in life (Haas, et al., 1989; Hay & Redon, 1999; Barela et al., 2003). Moreover, there exists some methodological concerns with regard to the lack of consistency of FOA instructions being used during experimentation. This directly influences where participants are guiding their attention and their interpretation of FOA cues (Davids, 2007; Petranek, et al., 2019). Further, the lack of replicability of traditional FOA studies and the increasing number of non-statistically significant findings in this research, calls into question the overall validity, both internal and external, regarding FOA instruction (Becker & Smith, 2013; Lawrence et al., 2011). Therefore, as a series of four complementary studies, the overall aim of this thesis is to further investigate these theoretical as well as procedural gaps. The first study examines which type of FOA instruction is best suited for two groups of young learners (typically developing children between 4-6 and 7-10 years of age) performing a postural control task. Participants will be randomized into either an INT, EXT or CTRL condition, where they will perform a postural control task with different respective visual displays. A force platform will be used to assess participants’ mediolateral centre of pressure (COP) performance, and electromyography (EMG) will be used to assess muscular activation of the participants’ major ankle stabilizers. The primary goal of study one is to investigate the influence of FOA in children by following the most common and traditional of FOA instruction. The second study serves as an extension for the first study. The aim of this study is to specifically investigate the validity and reliability of using FOA instructions, and whether or not the different attentional cues can drive their intended mental focus states. The method of this study is identical to those is Study 1 with a few major exceptions. In this case, two manipulation checks will be added to the procedure in order to assess how participants perceived, comprehended, and acted to their assigned FOA instructional condition. The first manipulation check is embedded in the structure of the trial itself: the comparison of postural control performance with and without visual information, modeled after the technique used in Yeh and colleagues (2016). The second manipulation check will be a retrospective verbal interview inspired by Perreault & French (2016). Finally, the third and fourth studies look to expand the research question from study one and two to different populations of atypically developing young learners who are known to struggle with both attention and postural control. Individuals with ADHD and individuals with DCD have been shown to interpret attentional and postural information differently when compared to age-matched controls. Therefore, the aim of these studies is to compare the differing effects of FOA across neurodiverse populations. Specifically, study three will use a group of young learners (from 4 – 10 years of age) with ADHD and study four will use a group of young learners (from 4 – 10 years of age) with DCD. The only differences in these studies compared to study one will be the lack of an age split and the use of EMG assessment. / Thesis / Master of Science in Kinesiology

<p>Two studies were conducted to examine the effects of learner-adapted practice on the self-efficacy beliefs, acquisition and retention of a motor task. Through a discovery process all participants learned to perform several keypress patterns, with the goal of completing each sequence as fast and accurate as possible. The first experiment had learners practice the keypress sequences in one of two adaptive schedules, which utilized either a ‘WinSwitch’ or ‘WinRepeat’ task switching algorithm, or follow a pre-determined order of tasks (two yoked-control groups). The purpose of this experiment was to determine if adaptive schedules were effective because they were tailored to a learner’s performance characteristics or due to the nature of the contextual interference employed by the switching algorithm when the 'winning' criterion was satisfied. To examine the psychological factors involved in adaptive practice, the second experiment had all groups practice in a ‘WinSwitch Adaptive’ schedule and manipulated the social-comparative feedback that was provided (positive, negative or control). Together these studies revealed that the effectiveness of adaptive schedules may not necessarily be due to the fact that they are tailored to a learner's performance characteristics. They also suggest that learning is facilitated by a switching algorithm that involves some blocked practice towards the beginning and mostly random practice towards the end of acquisition (WinRepeat schedule). However, providing positive social-comparative feedback can override the negative effects of the opposite schedule (WinSwitch) and result in more effective learning and increases in self-efficacy beliefs. These findings are discussed in reference to contextual interference effects and the self-efficacy framework.</p> / Master of Science in Kinesiology

<p>Our ability to control unstable objects highlights the sophistication of voluntary motor behaviour. In this thesis, we used an inverted pendulum (i.e., stick) balancing paradigm to investigate the task, learning and context-dependent attributes of unstable object control. We hypothesized that learning would mediate the functional integration of posture and upper limb dynamics and expected changes in the task demand and context to be reflected in the control of posture and the upper limb. We found that training increased the average length of balancing trials and applied this result to further investigate the circumstantial properties of unstable object control.</p> <p>We investigated the temporal structure of posture and upper limb dynamics using statistical and nonlinear time series analysis. We demonstrated that subjects used an intermittent strategy to control the inverted pendulum (Chapters 3 and 5) and found that motor learning modulated the statistical and spatiotemporal attributes of posture (Chapter 5) and upper limb displacements (Chapters 2, 3 and 5). We confirmed the balance control strategy was intermittent by showing that posture and upper limb time series are composed of two independent timescale components: a fast component linked to small stochastic displacements and a slow component related to feedback control (Chapters 3, 4 and 5). The interplay between timescale components was affected by the balancing context (Chapter 3) and task demand (Chapter 4).</p> <p>Chapter 5 investigated the acquisition of individual and coupled posture-upper limb control mechanisms. We found that motor learning involved two independent adaptation processes. The first process modified the timescale composition of posture and upper limb displacements and was followed by incremental changes in the occurrence and duration of correlated posture-upper limb trajectories. In Chapter 6, we investigated learning-mediated changes in multijoint coordination and control. Motor learning led to the flexible, error-compensating recruitment of individual joints and we showed that the preferential constraint of destabilizing joint angle variance was the putative mechanism underlying performance.</p> <p>This thesis performed a detailed examination of unstable object control mechanisms. The undertaken studies have provided knowledge about the acquisition and adaptation of control mechanisms at multiple levels of the motor system. Our data provide convergent evidence that the control mechanisms governing complex human balancing tasks are intermittent and modulated by the task and context.</p> / Doctor of Philosophy (PhD)

Human movement is inherently complex, requiring the control and coordination of many neurophysiological and biomechanical degrees-of-freedom, and the extent to which individuals exhibit variation in their movement patterns is captured by the construct of motor variability (MV). MV is being used increasingly to describe movement quality and function among clinical populations and elderly individuals. However, current evidence presents conflicting views on whether increased MV offers benefits or is a hindrance to performance. To better understand the utility of MV for performance prediction, we focused on current research needs in the military domain. Dismounted soldiers, in particular, are expected to perform at a high level in complex environments and under demanding physical conditions. Hence, it is critical to understand what strategies allow soldiers to better adapt to fatigue and diverse environmental factors, and to develop predictive tools for estimating changes in soldier performance. Different aspects of performance such as motor learning, experience, and adaptability to fatigue were investigated when soldiers performed various gait tasks, and gait variability (GV) was quantified using four different types of measures (spatiotemporal, joint kinematics, detrended fluctuation analysis, and Lyapunov exponents). During a novel obstacle course task, we found that frontal plane coordination variability of the hip-knee and knee-ankle joint couples exhibited strong association with rate of learning the novel task, explaining 62% of the variance, and higher joint kinematic variability during the swing phase of baseline gait was associated with faster learning rate. In a load carriage task, GV measures were more sensitive than average gait measures in discriminating between experience and load condition: experienced cadets exhibited reduced GV (in spatiotemporal measures and joint kinematics) and lower long-term local dynamic stability at the ankle, compared to the novice group. In the final study investigating multiple measures of obstacle performance, and variables predictive of changes in performance following intense whole-body fatigue, joint kinematic variability of baseline gait explained 28-59% of the variance in individual performances changes. In summary, these results support the feasibility of anticipating and augmenting task performance based on individual motor variability. This work also provides guidelines for future research and the development of training programs specifically for improving military training, performance prediction, and performance enhancement. / Doctor of Philosophy / All people move with some level of inherent variability, even when doing the same activity, and the extent to which individuals exhibit variation in their movement patterns is captured by the construct of motor variability (MV). MV is being increasingly used to describe movement quality and function among clinical populations and elderly individuals. However, it is still unclear whether increased MV offers benefits or is a hindrance to performance. To better understand the utility of MV for performance prediction, we focused on current research needs in the military domain. Dismounted soldiers, in particular, are expected to perform at a high level in complex environments and under demanding physical conditions. Hence, it is critical to understand what strategies allow soldiers to better adapt to fatigue and diverse environmental factors, and to develop tools that might predict changes in soldier performance. Different aspects of performance were investigated, including learning a new activity, experience, and adaptability to fatigue, and gait variability was quantified through different approaches. When examining how individual learn a novel obstacle course task, we found that certain aspects of gait variability had strong associations with learning rate. In a load carriage task, variability measures were determined to be more sensitive to difference in experience level and load condition compared to typical average measures of gait. Specifically, variability increased with load, and the experienced group was less variable overall and more stable in the long term. Lastly, a subset of gait variability measures were associated with individual differences in fatigue-related changes in performance during an obstacle course. In summary, the results presented here support that it may be possible to both anticipate and enhance task performance based on individual variability. This work also provides guidelines for future research and the development of training programs specifically for improving military training, performance prediction, and performance enhancement.

The changing nature of work and its competitive characteristics are global phenomena and are mainly fuelled by ongoing technological advancement. This creates unique challenges for talent attraction and the retention of high performing individuals. In addition, the global workforce is becoming more diverse due to demographic, societal and cultural changes and companies are placing greater demands on employee competency and performance. Managing the human factor as a strategic asset in organisations remains a primary challenge in securing a competitive advantage. The road construction industry in South Africa is no different. There is growing competition between civil engineering contractors to secure tenders and to maximise profitability. This is only possible with a sufficient and sustainable labour force. Valid selection processes are therefore required to ensure that the most productive individuals are selected for the most suitable jobs. Reliable and valid performance predictors will assist employers in making appropriate selection decisions. Selecting high performing individuals will support and enhance overall organisational performance. ix In this study the investigation focused on whether psychomotor ability and learning potential are statistically significant predictors of work performance - with specific reference to drivers and machine operators in a road construction company. A quantitative approach was followed to investigate the relationships between variables, or then the prediction of one dependent variable (driver and machine operator performance) by means of two independent variables (psychomotor ability and learning potential). Results from the study did not indicate any statistically significant relationships between the variables. Only scientifically validated assessment instruments were used in the study - which means the findings led to a renewed focus on the importance of performance measurement and the psychometric quality (reliability and validity) of performance data. / Industrial and Organisational Psychology / M.A. (Industrial and Organisational Psychology)