The role of noise in sensorimotor control

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The role of noise in sensorimotor control

Hamilton, Antonia Felicity de Courcy; (2003) The role of noise in sensorimotor control. Doctoral thesis (Ph.D.), University College London (United Kingdom). Green open access

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Abstract

Goal-directed arm movements show stereotypical trajectories, despite the infinite possible ways to reach a given end point. This thesis examines the hypothesis that this stereotypy arises because movements are optimised to reduce the consequences of signal-dependent noise on the motor command. Both experimental and modelling studies demonstrate that signal-dependent noise arises from the normal behaviour of the muscle and motor neuron pool, and has a particular distribution across muscles of different sizes. Specifically, noise decreases in a systematic fashion with increasing muscle strength and motor unit number. Simulations of obstacle avoidance performance in the presence of signal-dependent noise demonstrate that the optimal trajectory for reaching the target accurately and without collision matches the observed trajectories. Isometric force generation is also shown to have systematic changes in variability with posture, which can be explained by the presence of signal-dependent noise in the muscles of the arm. These results confirm the tested hypothesis and imply that consideration of the statistics of action is crucial to human movement planning. To investigate the importance of feedback in the motor system, the impact of static position on motor excitability was examined using transcranial magnetic stimulation and systematic changes in motor evoked potentials were observed. Force generated at the wrist following stimulation was analysed in terms of different possible movement representations, and the differences between force fields arising from stimulation over the cervical spinal cord and from stimulation over primary motor cortex are determined. These results demonstrate the structured influence of proprioceptive feedback on the human motor system. All the experiments are discussed in relation to current theories describing the control of human movements and the impact of noise in the motor system.

Type:	Thesis (Doctoral)
Qualification:	Ph.D.
Title:	The role of noise in sensorimotor control
Open access status:	An open access version is available from UCL Discovery
Language:	English
Additional information:	Thesis digitised by ProQuest.
Keywords:	(UMI)AAIU644284; Biological sciences; Motor control
URI:	https://discovery-pp.ucl.ac.uk/id/eprint/10103378