Weinberg, Isobel Claire; (2018) Expectation in motor planning and execution. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Expectation has been studied extensively in the decision-making field and its possible implementation in influential decision-making models has been formulated. Decision-making has historically been studied separately to motor planning. However, recent data suggest decisionmaking and motor planning overlap in time, with competing action plans in motor cortex biased by the ongoing decision. There has therefore been increasing interest in studying the interplay between decision-making and motor planning. Past experiments have typically studied the decision between two movements, when each movement is equally likely to be chosen. This aims to mimic the everyday situation in which we prepare a movement before knowing which it will be. However, a more common situation is that we expect to make one movement with a high likelihood, but also know there is a low likelihood of making a different movement. It is this uneven expectation across potential movements, and its effect on motor planning and execution, that is the focus of this thesis. I first investigate expectation in motor planning. I propose expectation may play the same role in motor cortical excitability as it is proposed to in theoretical decision making models. A series of experiment did not support this hypothesis; I discuss possible reasons for this. I next turn to an aspect of action execution: motor variability. There has been increasing interest in the idea that noise during motor planning is an important cause of motor variability. One theory has proposed that neural resources are divided when there are multiple motor plans, increasing motor variability. I propose that expectation interacts with this process by sharing these neural resources unevenly, so that variability is lower in the high-likelihood movement. I conduct two experiments to test this idea, and, based on the results, propose that expectation interacts with the motor control policy to determine motor variability.

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