PhD Candidate, Northwestern University
We demonstrated that besides of tactile sensation, rat whiskers were used to sense airflow.
My work has focused on quantifying the mechanical and neuronal responses of rat vibrissal system to airflow and on studying anemotaxis (wind-following) in rats. These studies offer important insights into neuroethology as well as into the development of novel sensing devices to sense fluid flow (both air and water) and track wakes. My results are likely to have multiple applications in several engineering domains.
Anemotaxis in rats: To determine the extent to which rats use their whiskers to sense airflow my colleagues and I trained a group of five rats to localize airflow and a control group of three rats to localize light. Trimming the whiskers reduced the ability of the rats to localize wind, but not light. This is the first study to investigate the cues that allow terrestrial mammals to detect and localize airflow. These findings shed light on an entirely new function for the rat whisker system which was previously studied only in the context of direct tactile contact.
Mechanical responses of rat vibrissae (whisker) to airflow: I developed a test-bed to investigate the mechanical responses rat vibrissae to airflow, and used three-dimensional (3D) video to quantify bending and vibrations of the whiskers. I then performed simulations to generalize these results across the rat vibrissal array, and simulated the effects of rat head orientation and rat whisking motions.
Neuronal responses in trigeminal ganglion (Vg) to airflow: To investigate how information about airflow is encoded in the vibrissal system, my colleagues and I quantified the responses of the vibrissal-responsive primary sensory neurons in Vg to airflow with different speeds and directions.
Abstract: Observation of terrestrial mammals suggests that they can follow the wind (anemotaxis), but the sensory cues underlying this ability have not been studied. We identify a significant contribution to anemotaxis mediated by whiskers (vibrissae), a modality previously studied only in the context of direct tactile contact. Five rats trained on a five-alternative forced-choice airflow localization task exhibited significant performance decrements after vibrissal removal. In contrast, vibrissal removal did not disrupt the performance of control animals trained to localize a light source. The performance decrement of individual rats was related to their airspeed threshold for successful localization: animals that found the task more challenging relied more on the vibrissae for localization cues. Following vibrissal removal, the rats deviated more from the straight-line path to the air source, choosing sources farther from the correct location. Our results indicate that rats can perform anemotaxis and that whiskers greatly facilitate this ability. Because air currents carry information about both odor content and location, these findings are discussed in terms of the adaptive significance of the interaction between sniffing and whisking in rodents.
Pub.: 24 Aug '16, Pinned: 29 Aug '17
Abstract: The survival of many animals depends in part on their ability to sense the flow of the surrounding fluid medium. To date, however, little is known about how terrestrial mammals sense airflow direction or speed. The present work analyzes the mechanical response of isolated rat macrovibrissae (whiskers) to airflow to assess their viability as flow sensors. Results show that the whisker bends primarily in the direction of airflow and vibrates around a new average position at frequencies related to its resonant modes. The bending direction is not affected by airflow speed or by geometric properties of the whisker. In contrast, the bending magnitude increases strongly with airflow speed and with the ratio of the whisker's arc length to base diameter. To a much smaller degree, the bending magnitude also varies with the orientation of the whisker's intrinsic curvature relative to the direction of airflow. These results are used to predict the mechanical responses of vibrissae to airflow across the entire array, and to show that the rat could actively adjust the airflow data that the vibrissae acquire by changing the orientation of its whiskers. We suggest that, like the whiskers of pinnipeds, the macrovibrissae of terrestrial mammals are multimodal sensors - able to sense both airflow and touch - and that they may play a particularly important role in anemotaxis.
Pub.: 01 Apr '16, Pinned: 29 Aug '17