Voluntary behaviors, such as chewing or locomotion, are produced by rhythmic neuronal circuits and can adapt to environmental changes. Some neurons participate simultaneously in two different neuronal circuits, known as dual activity. Ultimately, behaviors are produced by muscle responses to output of these circuits. Although muscles can switch between different rhythmic behaviors, I wanted to test the hypothesis that a muscle that typically expresses one pattern can participate in two patterns simultaneously when innervated by a dual activity neuron. To investigate this, I used a model rhythmic motor system in the crab Cancer borealis. Specifically, I dissected a nerve-muscle preparation and used extracellular and intracellular electrodes to stimulate the nerve and record from muscle cells, respectively. Stimulation patterns were created from previous recordings in order to mimic natural fast, and dual activity patterns. I found that the muscle innervated by the dual activity neuron was able to follow and participate in simultaneous dual activity. Therefore, a muscle within Cancer borealis can participate in two different rhythms at the same time when innervated by a neuron with dual-activity capability. The neuron that switches between single and dual activity contains a fast neurotransmitter that elicits the electrical responses and a neuropeptide with an unknown function. The next question to address is whether this neuropeptide contributes to the ability of muscles to switch to a rhythm different from their typical version. Understanding neuron-to-muscle communication is important for a better understanding of how rhythmic behaviors adapt to environmental changes. Further understanding of rhythmic behaviors and their neural circuits could contribute to better treatment of neuromuscular disorders or diseases. Personally, this project provided hands-on experience to develop skills, such as fine motor movement, scientific writing, and presenting results in a clean, concise manner, which I hope to utilize when attending dental school.
Author: Larissa Zeigler
Faculty Advisor: Dawn Blitz, Biology
Graduate Student Advisor: Savanna-Rae Fahoum, Biology
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