Quantification of odor-evoked IEG induction in the mouse OB. Signal intensity (arbitrary unit) of c-fos (A), Egr1 (B) and Npas4 (C) was calculated as the percentage of area positive for ISH signals in respective layers of the OB. Columns represented mean ± SEM. Seven to eight bulbs (approximately from + 4.5 mm bregma to + 4 mm bregma) from two to three mice were analyzed. Student's t-test was performed to compare means. ** Difference between groups was highly significant (p ≤ 0.01). * Difference between groups was significant (p ≤ 0.05).