Figure 6.

The c-Fos induction index of odor-stimulated mice indicates peak responsivity during the subjective night. The index was calculated as the number of c-Fos-IR cells within the specified brain region of odor-exposed mice divided by the number of immunopositive cells in the same region of mice not exposed to the odorant. From CT12 to CT20, the ratios of induced to spontaneously expressing c-Fos cells in the OB (a, b) and PC (c) were >1 (dashed line), indicating that circadian modulation activates responsiveness during the subjective night.