1 research outputs found
Analysis and modelling of the PY complex in the pyloric circuit of the crab stomatogastric ganglion
PhD ThesisCentral pattern generators (CPGs) are neural circuits that control rhythmic motor patterns
such as walking running and swallowing. Injuries can sever the spinal cord or
conditions such as Huntington's disease and Parkinson's disease can damage nerves from
the brain that control CPGs. Understanding the connectivity of neural circuits has
proved insu cient to understand the dynamics of such circuits. Neuromodulators and
neurohormones can di erentially a ect every connection in neural circuits and di erent
circuits are a ected in very di erent ways.
The resulting complexity of such systems make them very di cult to study but research
is greatly facilitated by the use of model organisms and computational models. The
crustacean stomatogastric ganglion (STG) has been used as a model system for many
years. Its relative simplicity and accessibility to neurons makes it an ideal system for the
study of neural interaction, CPGs and the e ect of neuromodulators on neural systems.
The e ect of dopamine on the pyloric CPG of the crab STG was recorded using voltage
sensitive dye imaging and electrophysiological techniques. To analyse voltage sensitive
dye (VSD) imaging data a heuristic method was devised that uses the timing of the activity
plateaus of neurons for the estimation of the dynamics of the temporal relationship
of the neurons' activities.
MATLABR
was used to create a Hodgkin-Huxley based model of the pyloric constrictor
pyloric dilator neurons (PDs) with parameters that could capture the dynamics of
neuromodulation. The MATLABR
model includes two compartments, the soma and the
axon, for the anterior burster neuron, the lateral pyloric neurons (LPs), two PDs and
ve individual pyloric constrictor neurons (PYs).
By di erentially changing the values of the model synapses, the model is able to reproduce
the de-synchronisation of the pyloric constrictor neurons as was observed experimentally
i
on the dea erented stomatogastric nervous system. Existing models model PYs and
PDs as single neurons. These models are unable to show the desynchronising e ect of
dopamine on multiple neurons of the same type. The model created for this research is
able to re
ect the e ect of neuromodulation on the complete circuit by allowing parameters
of synapses between neurons of the same type to be adjusted di erentially, re
ecting
the biological system more accurately