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Title: The contribution of top-down and bottom-up processes during observational practice
Author: Roberts , James W.
ISNI:       0000 0004 2746 9407
Awarding Body: Liverpool John Moores University
Current Institution: Liverpool John Moores University
Date of Award: 2012
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available