Annual Report 2009 - Department of Zoology - University of ...

Neurobiology
The group aims to understand neural mechanisms
that relate directly to the behaviour of an animal.
We focus on sensory processing (visual, auditory,
proprioceptive), motor control and plasticity in
the accessible nervous systems of insects and
lampreys. Our approach crosses the boundaries
from neurochemistry to from the function of neural
circuits and theoretical modelling and ethology.
Malcolm Burrows analyses neural processing in
local circuits of sensory, motor and interneurons that
control natural limb movements and the mechanisms
of jumping in insects. Berthold Hedwig studies
acoustic communication in insects: auditory pattern recognition, the motor control of singing behaviour, the mechanisms
that modify audition during the songs and the Calcium dynamics in single neurons. Simon Laughlin combines
experiment and theory to analyse the molecular and cellular factors that determine the abilities of synapses, neurons and
circuits to code, transmit and process information.
Jeremy Niven: Biophysical constraints on eye evolution
Swidbert Ott: Mechanisms of neural plasticity during
swarm-formation in the locust
Nicon Rasumov: The energy efficient brain
Stephen Rogers: Neuronal correlates of phase change in
locusts
Locusts use vision to target forelimb placement during walking
Jeremy Niven
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Biswa Sengupta: Information theory in neural cocking
Patricio Simoes: The effect of phase change in memory
and learning in desert locusts
Gregory Sutton: Biomechanics and neural control of
jumping
Accurate limb placement helps animals and robots to walk on substrates that are uneven or contain
gaps. Visual information is important in controlling limb placement in walking mammals, including
humans, but has received little attention in insects. We investigated whether desert locusts
(Schistocerca gregaria) walking along a horizontal ladder use vision to control limb placement.
Analysis of high-speed video footage showed that ladder-walking locusts targeted their front legs
to specific rungs in the absence of any previous contact, suggesting that visual information alone
is sufficient for targeting single steps. Comparison between the proportions of missed steps before
and after monocular occlusion showed that monocular visual information was used to place the
ipsilateral but not the contralateral front leg. Accurate forelimb placement also depended upon
mechanosensory inputs from the antennae as well as proprioceptive feedback from the ipsilateral
but not the contralateral forelimb. Locusts with monocular occlusion compensated for the loss
of inputs to one eye by immediately altering their stepping pattern to favour the forelimb nearest
the eye through which they could still see, emphasising the importance of vision in the control of
forelimb placement. Changing the rung position after the initiation of a step showed that targeting
of the front leg depends on visual information acquired before but not during a step. The trajectory
of the forelimb was modified only after missing the rung. This is in contrast to humans, which can
modify their leg trajectories during a step. Taken together, our data show that locusts walking in
environments where footholds are limited use visual and mechanosensory information to place their
front legs.
References
Niven, J.E. et al. (2010). Visual targeting of forelimbs in ladder-walking
locusts. Current Biology, 20, 86-91.
High-speed video footage of an adult desert
locust walking on a horizontal ladder. The
forelimbs are targeted to each subsequent
rung without having previous contact, showing
that vision is used for targeting limb placement.