[Comp-neuro] Competition funded PhD position on computational sensorimotor control @ U of Birmingham and U of Warwick

Sang-Hoon Yeo s.yeo at bham.ac.uk
Wed Nov 6 16:32:01 CET 2019


Title: The integration of visually-guided interception with balance
Supervisors: Dr R Reynolds (Bham), Dr Sang-Hoon Yeo (Bham) and Prof James
Tresilian (Warwick)
Type: Competition Funded PhD Project (European/UK Students Only)

Project Description
Control of fast interceptive movements is the highlight of human
sensorimotor behaviour, whose flexibility and adaptability far surpasses
that of any existing robot. The neural control mechanism of interceptive
movement remains elusive. For example, when an object that we are reaching
for moves unexpectedly, the hand is ‘magnetically’ drawn towards the new
object location. These trajectory adjustments occur within a remarkably
short latency (<100ms), do not require conscious awareness of the change,
and may rely upon sub-cortical neural circuitry[1]. We have demonstrated
that this exceptionally fast visuomotor system also controls the lower limb
when attempting to step onto a moving target [2]. However, when standing,
such automatic adjustments may threaten balance, which is also largely
controlled by sub-cortical brain circuitry. For example, reaching for a
moving object (e.g. catching a ball), causes a concomitant shift of the
centre of mass which disturbs the balance, but we rarely fall. The
apparently contradictory requirements of reaching and balancing must
therefore be somehow seamlessly integrated at a low neural level. Staying
upright in the face of such self-imposed perturbations is natural for
humans, but we still do not understand the underlying mechanism(s). For
example, attempts to implement such control into bipedal robots often leads
to catastrophic falls (see DARPA challenge https://bit.ly/1Il2QVS). This
failure to coordinate interception and balance can also lead to human falls
as a result of neural degeneration (e.g. ageing).

We plan to investigate the integration of these two systems, balance and
interception, at both a behavioural and neural level, to address the
following questions: How are balance and visually-guided interception
integrated, and what are the limits of this process? What neural circuitry
underlies this integration? How does normal ageing affect the integration
process, and what are the consequences for fall risk? We will address these
questions using a combination of techniques from Biomechanics,
Neurophysiology and Robotics. To study the integration of balance and
interception we will use virtual reality to present visual interception
targets. This will allow us to subtly manipulate the relationship between
hand and target motion [3]. Limb trajectory will be recorded using motion
capture and processed in real-time to manipulate visual feedback. Balance
will be simultaneously assessed by measuring ground reaction forces and
full-body motion capture. The limits of the integration process (i.e. when
do you fall?) will first be tested in young healthy individuals. To
understand the neural circuitry we will use Transcranial Magnetic
Stimulation (TMS)[4], Electromyography and H-reflexes. These techniques
will allow us to determine the relative contribution of cortical and
sub-cortical brain areas to these behaviours. This, in turn, will also have
relevance for understanding rehabilitation of balance following brain
injury. Finally, we will study older adults. This will determine the extent
to which the ability to combine interception and balance is compromised by
the ageing process, and the relevance for fall risk.

Funding Notes
This project is funded by the Midlands Integrative Biosciences Partnership.
MIBTP is a BBSRC funded Doctoral Training Partnership between the
University of Warwick, the University of Birmingham, the University of
Leicester and Aston University and Harper Adams University. Successful
candidates will start in October 2020.

Candidates can apply via the MIBTP website (Weblink coming here soon) but
are strongly encouraged to contact Raymond Reynolds for further information
prior to applying (r.f.reynolds at bham.ac.uk).

References
1. B.L. Day, P. Brown, Evidence for subcortical involvement in the visual
control of human reaching, Brain. 124 (2001)
2. R.F. Reynolds, B.L. Day, Rapid visuo-motor processes drive the leg
regardless of balance constraints, Curr. Biol. 15 (2005).
3. S.H. Yeo, D.W. Franklin, D.M. Wolpert, When Optimal Feedback Control Is
Not Enough: Feedforward Strategies Are Required for Optimal Control with
Active Sensing, PLoS Comput. Biol. 12 (2016).
4. W. Marinovic, C.S. Reid, A.M. Plooy, S. Riek, J.R. Tresilian,
Corticospinal excitability during preparation for an anticipatory action is
modulated by the variability of visual information, J. Neurophysiol. 105
(2011).
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