Long and Short Whiskers Help Guide and Regulate the Precision of Rat Orientation Behavior

Rat whiskers comprise an "active sensing" system involving two functional subdivisions: long whiskers for object localization and short whiskers for object recognition. To explore their respective roles in orientation, rats were trained in a reaching-grasping task. Specifically, four consecutive salient frames were identified in control rats: (i) whisker touch (Wt), the long whiskers came into contact with the front wall; (ii) first nose touch (Fnt), the rat brought the nose into contact with the wall; (iii) poke (Pk), the rat inserted its nose through the slot and placed short whiskers on the shelf, exploring it until the pellet was detected; and (iv) nose elevation (Nel), the rat raised its nose until reach start. These frames were used to subdivide orientation behavior into three specific phases: Wt-Fnt, Fnt-Pk, and Pk-Nel. To determine their respective roles in orientation, the rats performed the task after either long whiskers trimming or short whiskers shaving. Data evidenced a temporary loss of orientation followed by a recovery specific to each experimental group. Trimmed rats presented incomplete trials with loss of invariance, longer Fnt-Pk duration, and an increased number of nose touches. Shaved rats displayed longer trial duration and longer Pk-Nel interval. This duality is explainable by a consecutive use of the two kinds of whiskers and confirms their different roles in the multisensory integration necessary for each orientation phase. The data suggest that the long whiskers can be viewed as a spatial orientation system acting as a precision mechanism guiding head position in the context of coherent behavior.