The effects of reward on upper limb coarticulation

Sporn, Sebastian (2021). The effects of reward on upper limb coarticulation. University of Birmingham. Ph.D.

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Abstract

Coarticulation has been studied in speech production for over 100 years and more recently has been observed in upper limb movement sequences. Coarticulation of upper limb movements has been shown to underlie our remarkable ability to produce movement sequences such as drinking a cup of coffee or driving a car reliably, smoothly and fast. Crucially, coarticulation breaks down in Parkinson’s disease and stroke patients which significantly affects their daily lives. However, how humans learn to coarticulate and specifically how coarticulation can be facilitated is unknown. Reward is a powerful tool to influence human behaviour and over the past decade research on how reward shapes learning has widely increased. Importantly, reward has been shown to enhance execution of simple movements while converging evidence found that reward can improve learning of complex motor skills. The work in this thesis explores whether reward can enhance coarticulation. To address this question a novel motor task is introduced which involves a complex sequence of reaching movements (chapter 2). Across a series of behavioural experiments (chapter 3) we demonstrate that reward facilitates coarticulation which also led to improvements in movements smoothness and speed. Importantly, these improvements were retained over a long period without reward. Extending these findings, we used a neuropharmacological modulation (chapter 4) to investigate whether dopamine plays a role in coarticulation. The results suggest that a dopamine antagonist impairs coarticulation which can be compensated for with reward-based feedback. Finally, we show that coarticulation is guided by the principal of maximum smoothness which explains why coarticulation is constrained by the transition angle between reaching movements (chapter 5).

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):