Effects of altered olfactory experiences on the development of infant rats' responses to odors.

A "natural" olfactory learning paradigm was used to assess the effects of an altered perinatal olfactory environment on the development of odor-elicited behavior in young rats. Infant rats (from 3 to 12 days of age) reared by dams fed a eucalyptol-adulterated diet responded to the odor of eucalyptol with high levels of activity, mouthing, and probing, and also demonstrated a marked preference for that odor in a two-choice situation (Experiment 1). The effects were observed only in pups whose dam was fed eucalyptol-adulterated diet and were not observed in pups exposed to nonmaternal sources of odor. The intensity of behavioral activity elicited by eucalyptol odor varied, to some extent, with the concentration of the eucalyptol in the dam's diet during prenatal exposure (Experiment 2). Cross-fostering revealed that these effects were due almost entirely to the pups' postnatal exposure to the eucalyptol odor (Experiment 3). These findings indicate that novel odors specifically associated with the mother can gain control over orientation and ingestion-related behaviors.