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No description available.

In daily living activities motor control improves through adaptation. The experience from the daily living indicates that activation of the muscular function requires a full combination of predicting, anticipating and repeating the correct skills e.g. standing balance. For this adaptive process to be successful accurate somatosensory, visual and vestibular sensory inputs are required. With practice, the nervous system learns to correctly respond to sensory stimuli. Therefore, repetition and practising of multiple motor skill tasks are essential pre-requisites for functional improvement. The Targeted Training (IT) equipment has been used to treat children with neurological disorders. The theory of IT is based on the idea that external perturbations provide challenging tasks which allows the child to explore the development of balance control as well as stimulating all sensory systems that one associates with postural perturbations. Having knowledge about the potential of healthy children's responses to perturbation to Targeted Training can help to find out the expectation from children with neurological disorders by the process of adaptation to the same device. The overall aim of the study programme was to determine the neuromuscular co-ordination and adaptation to Targeted Training (IT) in healthy children. This aim was achieved by: (a) Production of a working system using the IT apparatus combined with XSens 3D orientation sensor and Surface Electromyography (sEMG); (b) establishing the validity of the XSens sensor; (c) establishing the repeatability of sEMG. Study 1 aimed to establish the accuracy of the XSens sensors with respect to the Qualisys Track Manger (QTM) camera based motion capture system which can be regarded as a 'gold standard' measurement of 3D position and orientation. In the validity study XSens sensors, consisting of a wearable motion capture system which is able to calculate roll, pitch and yaw in real time and outputting calibrated 3D linear acceleration, and the Targeted Training Equipment (ITE) were used in order to produce the same amplitude and frequency of movements for each trial. The angle produced from the QTM was compared to two angles derived from the XSens Pitch and the angular velocity from the gyroscope, by calculating Root Mean Square Differences (RMSD). A significant association was found between the QTM and XSens systems producing less than I degree error in the angle between the two systems tested for a dynamic position. Therefore XSens sensor is a suitable device for tracking the different positions of movement in the clinical area. Study 2 aimed to establish the repeatability of sEMG on selected right and left paired muscles of Rectus Abdominis (RRA & LRA) and Para Spinal (RPS & LPS) within-session and between-sessions, during bending forward and backward in functional tasks on four healthy subjects. The results of the investigation showed moderate repeatability in the three trials for subjects one and two. The values for subject three and four both within and between sessions were lower. However, these values were lower than those reported in the literature, therefore, the repeatability of sEMG data in the selected task was considered to be moderate to good. Study 3 aimed to develop a working system using the ITE combined with inertial XSens sensor recording 3D orientation and surface electromyography by applying the external perturbations to standing position in order to determine the neuromuscular co-ordination and adaptation to Targeted Training (IT) in children. After several trials were applied to children's standing balance in the ITE, results were statistically significant by the main effect of trial number on activated muscle responses in typical IT movements. A significant reduction in head-pelvis angle over time was found. Also all muscle groups from the three different segments of neck, trunk and thigh showed a large reduction of activity over time, the largest reduction was for the thigh muscles and the lowest was for neck muscles. The main finding was that the healthy children adapted to the IT task after the third session by using less muscle activity to control their balance against external perturbation. iii •

The primary aim of this thesis was to examine the nature of the representation developed during observational practice. Chapter 2 (Experiment 1-2) investigated the stimulus properties required to learn novel motor skills and the processing mechanisms responsible for learning. Participants attempted a novel relative timing pattern performed on a computer. Following the observation of a novel relative timing pattern via an expert human model (biological motion, BM), constant velocity model (non-biological motion, NBM) or end-state timing information without the trajectory (goal-directed model, GOAL), there was significantly more accurate relative timing error for BM and NBM groups (BM < GOAL, CTL; NBM < CTL (ps < 0.05)) (Experiment 1). Therefore, sequence learning through observation requires the presence of motion information, irrespective of the biological properties. These findings were extended with participants observing biological- or non-biological motion after receiving an instruction that the stimuli were in fact human- or computer-generated (BM-H, BM-C, NBM-H, NBM-C) (Experiment 2). In addition to the test of motor learning, participants completed a crecognition test featuring the detection of previously observed (trained) or novel (new) sequences. The results confirmed significantly more accurate relative timing error for the experimental groups compared to a CTL group. However, the recognition test revealed an attenuation of explicit recognition toward the observation of new sequences for the BM-H group compared to BM-C (p = 0.06), NBM-H and NBM-C groups (ps < 0.05). This indicated implicit motor learning that was specific to BM-H group. Thus, the coding of motion information was subject to top-down processes (i.e., belief), which modulate automatic bottom-up processes sensitive to biological motion. 3 Chapter 2 (Experiment 3-7) focused on the coding of biological kinematics. Thus, the natural movement profile adopted by humans was manipulated by forming an unnatural biological motion model featuring a shift in the proportion of time to peak velocity. The coding of biological kinematics would be indicated by the transition from natural movement kinematics, characterised by an early-to-mid time to peak velocity, toward a novel movement profile featuring a delayed time to peak velocity. Performance was measured by calculating the absolute difference between participant and model pTTPV (imitation error) and pTTPV of segment 1. The results revealed that the observation of unnatural biological motion produced significantly more accurate imitation error and an extended pTTPV, as per the unnatural model (p < 0.05) (Experiment 3). Subsequent experiments were intended to examine the processing mechanisms responsible for the coding of kinematics. Indeed, issuing a secondary movement task during observational practice led to an attenuation of the unnatural kinematics as indicated by no significant differences in imitation error and pTTPV between participants observing natural and unnatural biological motion (p > 0.05) (Experiment 4). This motor interference was effector-independent as indicated by the corresponding attenuation of imitation error and pTTPV after performing secondary movements of an unrelated effector (i.e., foot) (Experiment 5). These results indicate the coding of novel biological kinematics incorporate motor processes typically associated with action-execution. Meanwhile, the coding of biological kinematics was also subject to the direction of attention. That is, a secondary attention demanding counting task attenuated the coding of biological kinematics as there were no significant differences for imitation error and pTTPV (p > 0.05) (Experiment 6). Finally, the instruction to primarily attend to the trajectory compared to a general pre-cue led to a significantly more accurate imitation 4 error score, although significantly attenuated relative timing ~rror (ps < 0.05) (Experiment 7). Together, these results demonstrate the contribution of bottom-up and top-down processes during observational practice.

Orientador : Iverson Ladewig / Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Biológicas, Programa de Pós-Graduação em Educação Física. Defesa: Curitiba, 2004 / Inclui bibliografia e anexos

This thesis focuses on tactile perception and aims at a comprehensive analysis of its characteristics over the time-course of various goal-directed movements. Tactile perception is assessed by means of discrimination and detection paradigms, as well as event-related potentials (ERPs). The main question investigated throughout the thesis is: ‘What changes in tactile perception, if any, take place over the time course of a goal-directed movement?’ In Chapter 2, the mechanisms related to such identified changes are examined: a facilitatory one – attention, and an inhibitory one – suppression. The experiment in Chapter 3 tests, at a brain level, amongst several explanations of the experimental results outlined in Chapter 2: timing-based, effector-based, and modality-based attentional/suppressive influences. In Chapter 4, other naturalistic movements are investigated (i.e., the movements involved in juggling and throwing/catching a basketball). The results indicate a lack of facilitation in the processing of tactile information during the preparatory phase of the movement. Furthermore, differential changes are identified in tactile perception over the execution phase of the movement: At a behavioural level, tactile sensitivity significantly declines over the execution phase of the movement (though the detection of incoming tactile stimulation is enhanced), while at a neuronal level the same period exhibits significantly enhanced responses to somatosensory stimulation. The experiments reported here thus bring evidence in favour of a dissociation between detecting and discriminating what is felt while moving. These results suggest that the quality of what is felt while moving may not be important for movement and, at the same time, that different pathways in the brain may be responsible for detecting and discriminating what is felt over the time course of a goal-directed movement. Based on these findings, in Chapter 5, the implications of these results are discussed and directions for further research are outlined.

Le feedback auditif se définit comme un signal auditif qui contient de l'information sur un mouvement. Il a été montré que le feedback auditif peut guider le mouvement en temps réel, mais son influence sur l'apprentissage moteur est moins clair. Cette thèse a pour but d'examiner l'influence du feedback auditif sur l'apprentissage moteur, en se focalisant sur le contrôle temporel des mouvements. Premièrement, nous étudions l'apprentissage moteur chez les non-musiciens sains et montrons qu'ils bénéficient de l'information temporelle contenue dans le feedback auditif et qu'ils sont sensibles aux distorsions de cette information temporelle. Deuxièmement, nous appliquons ces connaissances à la réhabilitation de patients cérébro-lésés. Nous trouvons que ces patients améliorent leurs capacités de mouvement mais ne dépendent pas de la correspondance temporelle entre le mouvement et le son. Paradoxalement, ces patients ont même bénéficié des distorsions temporelles dans le feedback. Troisièmement, nous étudions les experts musicaux, car ils ont établi des liens particulièrement forts entre leur mouvement et le son. Nous développons de nouveaux outils d'analyse qui nous permettent de séparer les déviations temporelles en variation systématique et non-systématique. Le résultat principal est que ces experts sont devenus largement indépendants du feedback auditif. La proposition centrale de cette thèse est que le feedback auditif joue un rôle dans l'apprentissage moteur de la régularité, mais la façon dont le cerveau l'utilise dépend de la population étudiée. Ces résultats donnent une nouvelle perspective sur l'intégration audio-motrice et contribuent au développement de nouvelles approches pour l'apprentissage de la musique et la réhabilitation / Auditory feedback is an auditory signal that contains information about performed movement. Music performance is an excellent candidate to study its influence on motor actions, since the auditory result is the explicit goal of the movement. Indeed, auditory feedback can guide online motor actions, but its influence on motor learning has been investigated less. This thesis investigates the influence of auditory feedback in motor learning, focusing particularly on how we learn temporal control over movements. First, we investigate motor learning in non-musicians, finding that they benefit from temporal information supplied by the auditory signal and are sensitive to distortions of this temporal information. Second, we turn to stroke patients that are re-learning motor actions in a rehabilitation setting. Patients improved their movement capacities but did not depend on the time-locking between movements and the resulting auditory feedback. Surprisingly, they appear to benefit from distortions in feedback. Third, we investigate musical experts, who arguably have established strong links between movement and auditory feedback. We develop a novel analysis framework that allows us to segment timing into systematic and non-systematic variability. Our finding is that these experts have become largely independent of the auditory feedback. The main claim defended in this thesis is that auditory feedback can and does play a role in motor learning of regularity, but the way in which it is used varies qualitatively between different populations. These findings provide new insights into auditory-motor integration and are relevant for developing new perspectives on the role of music in training and rehabilitation settings