Design, Fabrication and Development of a Novel Flexible Electromyographic Electrode Array to Study Neural Control of Adaptive Locomotion in Soft-bodied Animals.
major advances in understanding the organizational principles underlying motor control
have focused on a small number of animal species with stiff articulated skeletons. These
model systems have the advantage of easily quantifiable mechanics but the neural codes
underlying different movements are difficult to characterize because they typically
involve a large population of ... read moreneurons controlling each muscle. This arrangement also
makes it difficult to study how neural codes drive adaptive changes in behavior. This
problem is highly simplified in the larval stage of the tobacco hawkmoth Manduca sexta
because of its unique motor innervation pattern: each muscle is innervated by one,
occasionally two, excitatory motor neurons. This arrangement allows the electrical
activity of each muscle to be mapped to individual motor neurons. Furthermore, there is
no complicating influence of inhibitory activity. As a result, by correlating
electromyographic (EMG) events to spikes in motor neuron activity, muscle activation
patterns can be converted into specific motor neuron activation patterns. Using these
patterns of spike activity, the mechanical responses of the muscles during natural
strain cycles can then be quantified through in-vitro work loop analysis. To acquire
motor patterns underlying adaptive locomotion, I employed a newly developed flexible
micro-electrode array specifically designed to record high resolution muscle activity
from Manduca muscles during crawling and climbing. Because of the high signal
selectivity of the electrode array, it was possible to identify single excitatory
junction potentials (EJP) within the composite EMG signals and relate the firing
activity of single motor neurons to behavior. The hypothesis that soft-bodied animals
like Manduca exploit self-adaptive properties of muscles to simplify motor control when
presented with environmental changes, such as changes in crawling orientation, was
tested. Not only were changes in Manduca crawling kinematics identified for the first
time, but the timing of muscle activity was also found to be highly dependent of the
orientation of the plane of motion, suggesting a more direct involvement of the CNS in
Manduca adaptive behavior than previously
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Neuroscience.
Advisor: Barry Trimmer.
Committee: Daniel Cox, Eric Frank, and Robert Olberg.
Keywords: Neurosciences, Biology, and Biomedical engineering.read less