Figure 1. A simultaneous pairing of whisker stimulus (WS) and olfactory stimulus (OS) leads to whisker-induced olfaction responses.

WS and WS-test consisted of mechanical pulses at 5 Hz and an intensity of evoking whisker response. OS was butyl acetate pulse that sufficiently evoked olfactory bulb response. Stimulus durations were 20 seconds. (A) A mouse was placed in the central arm of “T” maze. The object coated with butyl acetate is placed in an arm, and the object without butyl acetate is placed in another arm. The distance from the objects to the center is set in a situation that the mice before training and in control are just unable to identify butyl acetate. This 50% selection rate indicates a minimal concentration of their olfactory sensitivity. While stimulating their whiskers, the recall of smelling butyl acetate drives the mice moving toward the control arm. The moving traces in CR-formation mice indicate their preference away from butyl acetate. (B) shows the percentage of selecting control arm versus butyl acetate in the groups of OS/WS-pair mice (left columns) and OS/WS-unpair control (right) before (white bars) and after trainings (grays). The high rate of selecting the control arm are observed in the OS/WS-paired mice with whisker-induced olfaction response (p<0.01, n=24; paired-test for comparisons before versus after training; and ANOVA for the comparison among groups).