Non-Nutritive, Thermotactile Cues Induce Odor Preference in Infant Mice (Mus musculus)

Mouse pups (Mus musculus) placed on the midline of a mesh floor suspended over an empty area bounded by 2 odor fields, 1 containing homecage bedding and the other clean bedding, preferentially selected the homecage area when tested on postnatal day (PD) 5, 10, or 12. PD5 pups given a choice of homecage bedding versus age-matched bedding from another litter showed no discrimination, whereas PD10/12 pups preferred own home odors. To test whether such home orientation can be shaped by experience, pups were placed for 2 hrs on PDs 8 and 9 with either a lactating dam, a nonlactating foster dam or a warm tube bearing 1 of 2 novel odors. Other pups were similarly exposed to scented gauze to test whether mere exposure (familiarization) to an odor could induce a preference. Pups naïve to both test odors and those familiar with 1 odor showed no preference for either odor on PD10. Pups placed with a lactating dam spent significantly more time over the conditioned odor. Moreover, pups placed with the nonlactating dams or the warm tube also preferred the conditioned odor, indicating that the preference can be attributed association with non-nutritive, thermotactile cues.