Date of Award
Doctor of Philosophy (PhD)
School of Biological Sciences
The goal of the following research was to investigate the contributions of neural networks in selecting distinct variants of rhythmic motor activity. We used the premotor commissural ganglion (CoG) in the stomatogastric nervous system of the Jonah crab to understand how this network effectively controls the rhythms produced in downstream motor circuits. Prior research determined that individual CoG neurons are necessary to mediate sensory-induced variation in the effected motor patterns. However, single premotor neuron inputs to the STG are not sufficient to recreate the patterns induced by the selective activation of sensory pathways. Thus, it was hypothesized that the CoG-mediated effects on these sensorimotor transformations must be explained at the level of CoG population activity.
We embraced the exploratory nature of this study by approaching it in three phases. First, we established voltage-sensitive dye imaging in the stomatogastric nervous system, as a technique that reports the simultaneous activity of many neurons with single-neuron resolution. In short, this form of imaging was effective at reporting both slow and fast changes in membrane potential, and provided an effective means of staining fine neural structures through neural sheaths, structures that often act as barriers to many substances. Then, we characterized the distribution of somata in the CoG, and found that soma location was not fixed in its location from animal to animal, but that clustering of CoG somata did occur near their different nerve pathway origins. Finally, we used the voltage-sensitive dye-imaging technique to investigate the CoG population under many different sensory conditions, and found that two different sensory modalities, one chemosensory and one mechanosensory pathway, differentially affected the balance of excited and inhibited (network activation) neurons found in the CoGs. Moreover, differences in the composition of CoG participants between modalities was not extremely robust. However, it differed enough so that both CoG participation and activation were drivers of the observed changes in the downstream pyloric motor network, providing support for a premotor combinatorial code for motor pattern selection.
Goldsmith, Christopher John, "A Combinatorial Premotor Neural Code: Transformation of Sensory Information into Meaningful Rhythmic Motor Output by a Network of Heterogeneous Modulatory Neurons" (2018). Theses and Dissertations. 826.