Sensory input often can be enhanced by specific behaviors for looking, listening, sniffing or feeling. Rodents have large facial whiskers, the vibrissae, that are used to investigate objects by touch. Studies on anatomy and physiology of the rodent vibrissal system have examined cellular mechanisms of both sensory integration and the role of experience during development, particularly in relation to the somatosensory cortex of the brain. Sensory capabilities of the vibrissae themselves usually have been inferred from gross deficits seen after whisker removal, but little is known about how well these hairs can detect or discriminate various natural stimuli. This project uses a novel approach to determine how the vibrissae are used in behavior to make sophisticated tactile discriminations. Blindfolded animals will be trained to distinguish between surfaces of calibrated roughness; there is evidence that the rodents can discriminate with vibrissae at least as well as primates using fingertips. Video-based analysis will quantify amplitude, frequency, speed, and relations of whisker movements and head movements. The role of sensory input during development will be tested by trimming rows of whiskers of neonatal rats until they are 45 days old, then allowing whisker growth. This manipulation is known to produce abnormalities in the somatosensory cortex of the brain, and expected to produce discrimination deficits in the adults. Behavioral strategies will be compared between normal and neonatally deprived animals, to see how whisker movements are used to discriminate, and whether new strategies are learned. Finally, the whiskers will be studied as they interact with the surface, and the time patterns of whisking will be compared to the timing of excitation and inhibition seen in nerve cells in the somatosensory cortex. These novel studies will fill a critical gap in our knowledge relating brain function to tactile behavior; results will have a high impact not only on somatosensory science, but on sensory science and neurobiology, and on studies of learning and behavior.
