Doctoral Dissertation Research: Neurovascular structures of the trigeminal nerve and their relationship to diet in primates

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This doctoral dissertation project will examine the quantity and path of nerves that run through the jaws and teeth of mammals to establish if the size of these nerves is related to diet. The investigator will focus on humans and non-human primates, to determine if different diets correspond to the concentration of soft tissues (like nerves, arteries, and veins) in specific sections of the mouth and teeth. The research will advance knowledge about the relationships between soft tissues, bony tissues, jaw function, and diet, and may also inform our understanding of craniomandibular plasticity in modern humans. The project will support undergraduate and graduate STEM training, create an open, online database of scan data, and be used in a variety of science outreach projects and blog posts aimed at K-12 and general public audiences. Primates use sensory mechanisms to choose foods based on color, taste, size, and texture. These sensory mechanisms are controlled by nerves in the skin, eyes, mouth, teeth, and other structures that allow a primate to determine if a food is safe for eating. The primary nerves that supply sensation to the mouth are branches of the trigeminal nerve that pass through the maxilla and mandible. Previous research indicates that larger nerves relay more sensory information at faster speeds, suggesting that it is important to know the size of nerves to understand their functions. It has also been established that primate diets are intimately tied to tooth shape and chewing function, suggesting that the properties of teeth and their accompanying nerves are selected for simultaneously in relation to how they sense the properties (i.e., toughness, stiffness) of foods. The proposed work will use microCT scanning and iodine staining methods to examine the relationship between tooth shape and the nerves of teeth, with a focus on how these structures vary in relation to primate diets. Teeth of primates that are adapted to leaf- or insect-eating are predicted to need more nerves in the back of the mouth (under the molars), while fruit-eating primates are expected to have more nerves at the front of the mouth. This hypothesis is supported by data showing that individuals eating tougher diets manipulate food objects within their mouth more than individuals that consume softer food objects. This manipulation is partly due to how primates use nerves to assess material properties of an object to ensure that the individual does not damage their teeth during chewing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.