(A) Diagram of experimental set up. The mouse is head-fixed in the virtual burrow and an air puff is delivered to the nose. (B) Left, burrow position over time showing a single ingress in response to a strong air puff (gray box, 200 msec, 80 psi). Upward deflections correspond to burrow movement towards the animal’s head (ingress). Right, 15 ingress responses from a single animal to 15 air puffs. Dashed box at left demarcates epoch in which time scale is expanded at right. (C) Example of flinch in response to weak air puff. Downward going, approximately 2 Hz oscillations correspond to the animal’s breathing cycle. Upward going low-amplitude, transient deflection corresponds to startle in response to air puff (gray box, 20 msec, 2 psi). (D) Diagram of tube (top) and platform (bottom) variants. Air puffs are directed either at the snout (top, orange and bottom, pink) or at the hindquarters (top, green and bottom, blue). (E) Mean change in burrow position in response to air puff (gray box) across all animals and all trials (N = 4 animals, three trials each, per condition); same color scheme as in previous panel. (F) Change in burrow position at T = 1.5 s relative to pre-stimulus epoch, pooled across animals and trials. A Wilcoxon rank-sum test was employed to evaluate whether the change in burrow position differed significantly (p(tube-front,tube-back)=0.71, p(tube-front,platform-front)=9.7×10−05, p(tube-front,platform-back)=3.7×10−05, p(tube-back,platform-front)=9.7×10−05, p(tube-back,platform-back)=6.0×10−05, p(platform-front,platform-back)=0.078, N = 4 mice, three trials each, per condition). Individual trials, gray points. Normalized, smoothed histogram, light gray shading. Median, red line. *** indicates p<0.001, n.s. indicates p≥0.05.