Sensory Feedback and Neuromechanical Locomotion
As a
result of the year long immersion program at College Park in
A. Cohen's biology lab, I developed a research program in sensory
feedback in neuromechanical locomotion in collaboration with an
international multidisciplinary group of researchers focused on how
the lamprey swim.
We are concerned with developing, understanding and
analyzing components of lamprey swimming: from nerve conduction along
an axon, to muscle contraction and body dynamics to interaction with
the fluid environment. Then using those components to make the model
lamprey swim. The group is a consortium of researchers from UMCP,
Princeton, JHU, Tulane, and St. George's Medical School in London.
Based on our ongoing collaboration and yearly meetings, NSF recently
awarded us a Research Coordination Network in the Physical and Life
Sciences grant (PIs L. Fauci and A. Cohen). The grant is designed
to support communication and coordination of our research efforts
across disciplinary, organizational, institutional and geographical
boundaries. As part of this multi-institution effort, I am chairing
the organizing committee (consisting of myself, N. Cowen (JHU) and
A. Smits (Princeton)) of the first annual Winter Workshop on
Neuromechanical Locomotion at Princeton University, January 2012. The
grant will also facilitate travel to conferences, extended visits, and
interdisciplinary collaborations for ourselves and our students to
interact with other members of the community. The group listed above
serves as a steering committee and is tasked with
distribution of funds.
My focus on this project was to understand sensory input into the
central pattern generator, which consists of a group of neurons in the
spinal cord that control vertebrate locomotion. This work has been
funded by an NSF grant for interdisciplinary work in the mathematical
sciences, as well as an REU
supplement for my student Geoff Clapp.
To date, I have three major contributions to the field of
vertebrate locomotion:
- Analyzing the effects of random connections in the central
pattern generator In this work, which appeared in the J. Computational
Neuroscience, I showed that random
connections between oscillators approach a deterministic limit.
- Studying entrainment ranges for the phase model The simplest
mathematical model of the central pattern generator is a called a
phase model, in which each oscillator is modeled by a single variable,
called the phase.
I developed analytical expressions for the
entrainment ranges of the phase model for two different network
architectures.
The results from the
phase model indicate that experimental results on the central pattern
generator are not generic for chains of coupled oscillators and imply
a non-uniform coupling asymmetry in the connections between
oscillators.
Additionally, we were able to
completely classify loss of entrainment mechanisms. Results of this
work appeared in the Journal of Mathematical Biology.
- Studying entrainment ranges for a neural model
I considered a
neural model in which each segment of the central pattern generator
consists of three classes of neurons (excitatory, lateral inhibitory,
and crossed inhibitory). Along with my undergraduate student Geoff
Clapp, we have shown that
entrainment ranges from this work are similar to those of the phase
model. This result suggests that the non-uniform coupling
asymmetry that was needed to qualitatively reproduce experimental data
is not model specific, but represents a more robust phenomenon among
coupled oscillators, thus providing evidence for a possible coupling
scheme for the lamprey central pattern generator. This is an example
where modeling played an essential role in developing insight into
a biological system, since experiments to address these questions
are challenging.
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