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Maintaining upright posture is seemingly an automatic task in younger adults, but it may require additional resources in late adulthood due to decreases in sensorimotor and cognitive functions. The thesis used a dual-task paradigm to investigate age-related changes in relation to the secondary task and context-dependent factors attributes to postural control. The postural task involved visuomotor tracking. Successfully performing the visuomotor task necessitated proper sensory feedback, motor response, and sensorimotor integration. Moreover, we used silent counting as a cognitive task to investigate attentional demands on postural control and age-related difference in cognitive processing. We first investigated the relative contributions of visual feedback delay and cognitive task load on postural dynamics as well as age-related difference in this effect. Our results supported distinct timescale mechanisms for postural control. Moment-to-moment center of pressure fluctuations are dependent on cognitive performance during delayed visual feedback postural control. Also, we demonstrated the increased role of vision with age in postural control. Next, we investigated whether postural control improved when performing a cognitive task with an internal focus of attention. We found that devoting less attention internally by performing a cognitive dual-task enhanced postural control in young adults. Yet, the age-related declines diminish the attentional allocation ability. Lastly, we investigated how older and younger adults differ in employing sensorimotor strategies in a dual-task situation. Our results suggested that age-related changes in postural control may degrade the flexible coordination of the sensory feedback and motor execution. Furthermore, diminished cognitive and attentional capacities may alter postural performance in dual-task conditions. This thesis adds to the current understanding of the role of sensorimotor processing, attentional influence and age in the control of posture. Our data provide convergent evidence that deterioration of peripheral sensorimotor systems and reduced flexibility in central information processing are responsible for the age-related differences in postural control. Doctor of Philosophy (PhD)

When learning a new motor skill, how we choose to go about the learning process can influence how quickly and how well we learn the task. In particular, the role of learner involvement during the acquisition period can be manipulated through how practice is scheduled. Two separate sets of literature (progression of task difficulty and self-controlled practice) which discuss learner involvement during acquisition were reviewed. The motivation behind this thesis is to examine the effects of progressive and self-controlled practice on measures of retention, transfer and dual-task performance as well as to attempt to determine the underlying factors responsible for any benefits of each of these schedules. We examined the influence of practice scheduling during acquisition of a fine-motor skill within the context of the minimization and facilitation of learner involvement through a series of four experiments and one review paper. The findings of the four experiments suggest that an easy-to difficult progression through versions of a task, whether prescribed or chosen, does not always induce implicit learning processes and is also not always beneficial to performance under a secondary task load. The only manipulation that was found to have an effect on dual-task performance was, not the minimization of learner involvement but the proximity of the version of the task first practiced in acquisition to the tested version of the task. Participants that began practice using versions of the task most similar to the test version performed a novel task well under dual-task conditions and maintained this performance over time. The overall difficulty of versions of a task practiced in acquisition appears to have an influence on participants’ ability to perform well on immediate transfer tests and to maintain that performance on delayed transfer tests. These results suggest that learner involvement can be beneficial to performance on transfer tests. The possible benefit of cognitive involvement for learning of motor tasks found in the studies that examined the progression of task difficulty is consistent with one of the main explanations of the benefits of self-controlled learning summarized in the review paper. Interesting motivational implications found in study four, where motivational factors may have overridden the cognitive effort involved are also consistent with the findings summarized in the review paper from the perspective of the self-determination theory. The results and information presented in this thesis present implications for anyone responsible for organizing a practice of motor skills. The most beneficial organization of versions of a practiced task is dependent upon the goals of the testing context. Doctor of Philosophy (PhD)

This dissertation examined perturbation effects during complex tactile information transmission. The four experiments provide evidence regarding sensory and information processing demands in early stages of complex tactile learning. Experiment 1 established complex tactile learning behavioural performance. Vibrotactile stimuli representing Morse code letters were communicated to participants with or without induced perturbation to the finger of letter reception. Response performance was measured and augmented feedback was provided retroactively. Perturbation conditions lead to poor performance during tactile acquisition, but improved performance during application of knowledge. Experiment 2 determined if the experiment 1 results demonstrated masking or response competition paradigms. Target “masking” is the reduced ability to detect or interpret a stimuli pattern by presentation of other information (Craig, 1985; Verrillo, 1985). Response competition is the competition or distraction from target response generation by secondary stimuli (Craig, 2000; Bolanowski et al., 2000). Experiment 2 tested response competition by spatially separating the perturbation and tactile information delivery sites. Experiments 3 and 4 served to replicate behavioural acquisition data from experiments 1 and 2. They also extended the findings of the first two experiments by introducing neurophysiological measurement to reflect the changes associated with the two perturbation conditions. The study discerned whether the masking and response competition paradigms from experiments 1 and 2 were predominantly impacting the peripheral or central information processing. Results from the four studies collectively demonstrate that increased demands are placed on the sensory system during early stages of complex tactile learning when perturbation is spatially congruent with tactile information delivery. Experiments 1 and 2 revealed that attention does not supersede spatial location of perturbation, and perturbation location is paramount to yield sufficient interference to impede acquisition yet lead to enhanced knowledge retention and transfer. Experiments 3 and 4 determined that cortical information processing associated with complex tactile information acquisition are neurophysiologically differentiated when relative locations of meaningful and perturbation stimuli are congruent or spatially separated. The findings from this dissertation serve as an advancement of our understanding of masking and response competition phenomenon as they pertain to complex tactile learning. Doctor of Philosophy (PhD)

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. 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). 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. 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. Doctor of Philosophy (PhD)

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. Master of Science in Kinesiology

This thesis was specifically designed to explore the role of motor information in behavior and learning in the presence and absence of physical and cognitive challenges. The first experiment examined the role of motor information in the maintenance of standing balance. This study found that light touch (motor information) was most useful when visual condition was challenging, eyes closed. Increased benefit of touch in the presence of challenge suggests that motor information may provide similar information as other senses, and act in a compensatory fashion when those senses are challenged. The second study examined the role of motor information, in the form of enactment, in learning a motor communication task. Results from this study support a role for motor information in enriching the learning environment by strengthening memory to reduce rate of forgetting. The third study examined the role of motor information in disease, using motor-centric instruction and guided movements to teach persons with Alzheimer Dementia to bowl using the Nintendo Wii TM. The spared motor learning observed in these participants confirms claims in the literature of spared motor function in persons with dementia and strengthens the claim the motor system can provide compensatory information to support challenged cognitive systems. Taken together, these findings add to the current literature supporting motor pathways with information separable form other sensory pathways and spared motor capacity to learn in dementia. Doctor of Philosophy (PhD)

Two experiments are reported that examined whether KR was necessary to develop a representation through observational motor learning. Subjects observed a learning model perform three variations of a three segment timing task and then performed two transfer tasks. The first experiment found that a cognitive representation could be formed through observational learning, even when KR was not provided during acquisition. This was determined since there were no differences in performance of the two observer groups on the transfer tests. The observers were however, better than the control group on the transfer tests. Evidence for the development of a cognitive representation was also found when auditory information was eliminated during acquisition on the second experiment. Once again there were no differences in the perforrnance of the two observer groups. These results were discussed in reference to observational motor learning and the necessity of knowledge of results to acquire movement skills. Master of Science (MS)

Three experiments are reported that examined the lnfluence of prior judgements on implicit and expliclt tests of memory in gymnastic judging. The rationale was that if gymnastlc Judging ls affected by the memory for prior eplsodes, then the accuracy of judgements should change as a result of the prior episode. The results of Experiment 1 revealed that perceptual judgements dlffered as a functlon of an item's relationship between the study phase and the perceptual test phase. Moves that had the same performance ln both phases resulted ln the hlghest level of accuracy (M = 79%). New moves were less accurate (M = 75%). The lowest level of accuracy was achieved for items where the performance was altered between study and the perceptual test (M = 72%) . Similarly, recognition judgements differed as a functlon of an item's relationship between the study phase and recognition test phase. Novlce and expert Judges revealed similar memory lnfluences for perceptual and recognition Judgements (Experiment 1). Memory influences were reduced, but still evident when subjects were given prior knowledge of these effects and procedural changes were adopted (Experiment 2). Spacing of repetitions dld not enhance prior processlng effects of perceptual Judgements, but superior retention was noted for spaced repetitions in the recognition test phase (Experiment 3). These findings are discussed in terms of memory influences on subjective experience and the practical implications of Judges' exposure to an athlete's performance prlor to competition. Master of Science (MS)