UC Riverside Undergraduate Research Journal

The onset of parental care in female mammals is associated with plasticity in neural processing of infant-related sensory stimuli, which enhances mothers’ ability to detect and care for their offspring; however, little is known about sensory plasticity in fathers. We tested the hypothesis that parenthood alters neural responses to olfactory and auditory stimuli from infants in male and female California mice (Peromyscus californicus), a biparental rodent. Virgins and new parents of both sexes were exposed to a combination of a chemosensory stimulus (pup-scented or unscented cotton [control]) and an auditory stimulus (pup vocalizations or white noise [control]). Brains were collected one hour later and stained immunohistochemically for Fos, an index of neural activity. We quantified Fos in the main olfactory bulbs (MOB), a region essential to receiving olfactory information, and medial preoptic area (MPOA), a region critical for parental behavior. We predicted that Fos in MOB and MPOA would be greater in parents than virgins, especially after exposure to pup stimuli. We found that in females, MPOA and MOB Fos did not differ between virgins and mothers or across treatment groups. In contrast, fathers had lower expression of Fos in MOB but higher expression in MPOA, compared to virgin males. Moreover, Fos in MPOA was higher in males exposed to pup vocalizations and pup scent compared to those exposed exclusively to pup vocalizations. Fos in MPOA was also higher in males exposed to scent or both scent and vocalization stimuli compared to males exposed to control stimuli. These findings suggest that the onset of parenthood alters activity in the MOB and MPOA, especially in response to pup vocalizations and scents, in males but not females in this biparental rodent.