Figure 1.

A trial in an “Air-Track” plus maze with whisker tracking. A, Mice in a plus maze. A schematic of the Air-Track plus maze used for this study is shown here with a head-fixed mouse, navigating the maze. Mice were trained to rotate the maze away from a lane that had an LED light and kept rotating the maze around themselves to find the dark lane, which they entered, and traversed to the end, to obtain a milk reward. The mouse, the LED, and the location of the reward remained fixed in place; all that moved was the maze. B, Maximum intensity projection of a mouse, its painted whiskers, and nose. Left, The painted whiskers on each side of the face and a spot painted on the nose are shown in a single frame. Some of the adjacent, untrimmed whiskers are clearly visible. Right, Maximum intensity projection of 30 trials. The movement of the whiskers around the face of the mouse forms a halo composed of the two colors painted on the whiskers and reflects all the positions the two painted whiskers occupied in the course of 30 trials in the maze. Furthermore, the small spot painted on the nose transforms into a large spot over the course of the 30 trials, indicating that the nose moves a lot as the animal traverses the maze. C, A single decomposed trial of behavior and bilateral whisker motion. We tracked the motion of two whiskers (rostral one painted red, caudal one painted green) bilaterally for the duration of each trial. Once a trial ended, the lick tube was retracted, the LED light turned on, indicating that the mouse was in the wrong lane. At this point, mice often waited at the end of the lane without moving much (top, dark gray bar, standing still) for seconds to minutes, before they exited the lane by going backward (orange). Then the mouse turned and rotated the maze around itself (yellow), until the LED at the end turned off. Mice had to enter the dark lane and move forward into it (dark blue). At the end of the lane, they waited for the lick tube to descend (light gray, expect reward), and lick for the reward (purple). There was a delay between the end of the forward motion and the time for the lick tube to descend to the animal (reward expectation). Two whiskers on each side of the face, one painted red (rostral whisker) and the other painted green (caudal whisker), could be tracked for the extent of the trial. The position of the whiskers over the course of the trial was related to the behavioral epochs. Whisker motion was related to the animal's motion. Whisking was apparent when the animal was moving backward or rotating the maze or going forward. In contrast, when the animal was standing still, whiskers did not move much. And when the animal was licking the reward, the pattern of whisker motion was distinct (low amplitude, rhythmic, bilaterally symmetric) compared with epochs where the mouse was moving the maze.