Mechanisms for sensing fluid flow are well studied in arthropods and in some aquatic mammals, but we know very little about how terrestrial mammals detect and localize airflow (Chapter 1). In this thesis, I will describe a series of studies in rodents that investigate the behavioral, mechanical, and neural basis for vibrissal (whisker) based sensing of airflow. First (Chapter 2), my colleagues and I performed experiments to demonstrate that whiskers provide important cues during airflow sensing behavior. Rats trained on a five-alternative forced-choice airflow localization task exhibited significant performance decrements after vibrissal removal. In addition, following vibrissal removal rats deviated more from the straight-line path to the air source, choosing sources further from the correct location. In contrast, vibrissal removal did not disrupt performance of control rats trained to localize a light source. We next (Chapter 3) analyzed the whisker’s mechanical response to airflow in order to reveal the physical cues that could underlie the rat’s airflow sensing capability. Mechanical experiments showed that whiskers bend primarily in the direction of the airflow, they vibrate around their deflected position at frequencies near their resonance modes, and their bending and vibration magnitudes both scale with airflow speed. At low airspeed, whiskers vibrate parallel to the airflow direction, but, surprisingly, transition to perpendicular vibration at high airspeed. Third (Chapter 4), to investigate the neural basis for vibrissal-based airflow sensing, we recorded from trigeminal ganglion (Vg) neurons in anesthetized rats during presentation of an airflow stimulus at different speeds and from different directions. The average firing rate of Vg neurons increases with airflow speed, and depends on airflow direction. Additionally, the firing patterns of Vg neurons are related to the intrinsic vibration modes of the whisker. Together, these results demonstrate that the rodent vibrissal-trigeminal system, which has a well-established role in tactile detection and texture discrimination, also contributes significantly to airflow sensing and anemotaxis. Lastly (Chapter 5), we compare and contrast the whisker’s mechanical response to airflow and touch, and compared the rat whiskers with arthropods flow-sensing hairs and pinniped whiskers, and suggest a potential role for rat whiskers in sensing airflow during olfactory search.

Last modified

• 01/30/2019

Creator

• Yan S.W. Yu

DOI

• https://doi.org/10.21985/N27N1M

Subject

• Mechanical Engineering

Keyword

• Flow sensing
• Anemotaxis
• Wind
• Trigeminal
• Odor tracking
• Whisker

Date created

• 2017-01-01

Resource type

• Dissertation

Rights statement

• In Copyright