UC San Diego

There has been a strong presumption that the rodent vibrissae are fine tactile feature detectors, sensing position, shape, and texture of objects. However, how rat vibrissae extract fine surface features, and their quantitative acuity during texture discrimination remain unknown. The goal of this thesis is to elucidate the functions of the rat vibrissa system during fine texture discrimination at the behavioral level. The first goal of this thesis is to detail training strategies developed specifically for rodent vibrissa-dependent texture discrimination tasks. In Behavioral Setup 1, rats were trained to discriminate smooth vs. grooved aluminum surfaces, and to palpate across a moderate gap for water reward. In Behavioral Setup 2, rats were trained to discriminate between sandpaper of two different roughnesses, presented across a gap. Results showed that rats could learn texture discrimination in 8 weeks (Setup 1) and 2-10 weeks (Setup 2) of training. The second goal of the thesis was to examine the relative functional roles of the micro/macrovibrissa system during texture discrimination. The specific roles of the two systems are not known. We tested whether macrovibrissae are sufficient for fine texture discrimination by removing the microvibrissae. Microvibrissa trimming did not decrease performance indicating that macrovibrissae alone can support texture discrimination. We also investigated the acuity of the vibrissa system in identifying texture differences. Sandpapers were varied to measure the psychophysical limit of texture discrimination. Though results were only obtained in one rat, these observations suggest that rats can discriminate sandpapers with finer resolution than previously known