Primary Supervisor:Dr Tom Matheson, Department of Neuroscience, Psychology and Behaviour

Secondary supervisor: Dr Swidbert R. Ott

PhD project title: Adaptability of limb movement control following injury

University of Registration: University of Leicester

Project outline:

PhD projects in this area will investigate how animals control their limb movements. We are particularly interested in understanding the interplay between active muscle contractions and passive elastic properties of limbs that can assist or resist movements. As neurobiologists we are interested in comparative aspects (how do animals adapted to different ways of moving differ in their neurobiology and biomechanics?) and in uncovering general principles of operation. The work will span from comparative behaviour, through limb movement analysis to electrophysiological recordings of motor activity, with the balance of questions and techniques tailored to the specific interests and skills of the successful applicant. Our lab works with insects – particularly locusts – to address these questions.

Most animal movements are driven by muscle contractions controlled by the nervous system, but passive elastic forces, originating in muscles, tendons or other tissues, interact with these active forces in both vertebrates and invertebrates (Page et al. 2008). We have shown experimentally that meaningful movements can be generated by passive forces alone. Surprisingly, some of these forces arise within joints themselves (Ache & Matheson, 2013). Across species, where antagonist muscles have different strengths, passive joint forces seem to support the weaker muscle. We therefore hypothesise that passive joint forces are shaped by evolutionary adaptation and form an important component of effective motor control.

In related work we have shown that locusts 'recalibrate' their aimed limb movements following damage to joint sense organs. This plasticity allows animals to regain accurate movements in the face of sensory loss. Young adult locusts can similarly adjust their movements following the loss of part of a limb. Older adults do not readjust their movements after such injury, indicating that the ability to respond to damage decreases with age.

This PhD project will merge these strands of research to seek the mechanisms governing plasticity of motor control. The successful applicant will measure active and passive limb forces in a range of species to test our hypothesis that passive joint forces are matched to active forces acting at the same joint. Are there changes in passive forces in animals that learn new movement strategies to deal with limb damage? Is neuronal plasticity matched by plasticity in biomechanical properties? Do neuronal and biomechanical properties change during development and ageing?

The successful applicant will have opportunities to be trained in analysis techniques drawn from distinct zoological, behavioural, engineering and neurobiological disciplines to address fundamental questions in limb motor control, viewed from a comparative (evolutionary) functional perspective.

References:

1. Ache JM and Matheson T (2013) Passive joint forces are tuned to limb use in insects and drive movements without motor activity. Current Biology 23: 1418-1426. doi: 10.1016/j.cub.2013.06.024
2. Calas-List D, Clare AJ, Komissarova A, Nielsen TA and Matheson T (2014) Motor inhibition affects the speed but not accuracy of aimed limb movements in an insect. Journal of Neuroscience 34: 7509 - 7521. doi: 10.1523/JNEUROSCI.2200-13.2014.
3. Page KL and Matheson T (2009) Functional recovery of aimed scratching movements following a graded proprioceptive manipulation. Journal of Neuroscience 29: 3897 - 3907. DOI: 10.1523/JNEUROSCI.0089-09.2009

BBSRC Strategic Research Priority: Understanding the Rules of Life: Neuroscience and behaviour. Integrated Understanding of Health: Ageing

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Techniques that will be undertaken during the project:

Core techniques:

• Animal behaviour
• Limb kinematics
• Muscle force measurements
• In vivo electrophysiology

Possible further techniques:

• Micro-CT (X-ray micro-computed tomography)
• Finite Element Analysis
• Biomechanical modelling

Contact: Dr Tom Matheson, University of Leicester