Rapid and robust olfactory conditioning with milk before suckling experience: Promotion of nipple attachment in the newborn rat

An olfactory conditioning paradigm tested the hypothesis that newborn rats are able to Ic;Lm about events associated with their first experience with milk as early as 3-5 hr after birth. Exposure to lemon odor (conditioned st imulus. [CS]) paired with intraoral milk infusions (unconditioned stimulus, [US]) resulted in strong conditioning: In the presence of the CS, sustaine d attachment occurred to an empty nipple as if it provided milk, whereas pu ps in control conditions showed little attachment. A single CS-US pairing w as sufficient for strong conditioning, which was evident with a trace inter val as long as 60 s. Conditioning was robust enough to promote attachment t o a nipple providing saline, which is aversive to the newborn rat, and comp arably strong conditioning occurred with sucrose or saccharin as the US. Th ese findings suggest that olfactory conditioning has the potential to modif y suckling behavior.