CONDITIONED WHISKING IN THE RAT

The rat's mystacial vibrissae are active during exploratory and discri minative behaviors, with individual vibrissae serving as elements in a receptive array scanned across object surfaces. To facilitate neurobe havioral analysis of this sensorimotor system, we have developed an ex perimental paradigm that confines vibrissa movements to a defined phys ical location, makes possible on-line monitoring of ''whisking'' activ ity, and brings such activity under associative control using operant conditioning procedures. Rats were secured, and movements of an identi fied bilaterally homologous pair of vibrissae (right and left gamma st raddlers) were detected by laser-based photodetectors. Subjects were m aintained on a water deprivation schedule, and whisker movements were monitored during adaptation to the test situation and after the clippi ng of other vibrissae on both sides of the snout. Rats were reinforced with water delivery for emitting vibrissa movements in the presence o f a conditioned stimulus (tone) whose presentation was made contingent upon a prior period of nonwhisking. The rate and temporal distributio n of vibrissa movements were brought under experimental control by mea ns of interval and ratio reinforcement schedules. Although the procedu res provide minimal information about the kinematics or topography of conditioned vibrissa movements, they permit the investigator to manipu late response parameters normally under the voluntary control of the a nimal in a preparation amenable to neurophysiological analysis.