Olfactory learning in the rat neonate soon after birth

Abstract

The first hours of a newborn rat’s life entail locating and attaching to the mother’s nipple not only for nutrition but also for protection and warmth. The present study sought to characterize olfactory learning in the rat neonate immediately after birth. Newborn rats were exposed to an odor at various time periods soon after birth and tested for behavioral activation and attachment to a surrogate nipple in the presence of this odor at 4–5 hours postpartum. Regardless of when pups were presented the odor (0, 1, or 2 hours after birth) motor activity was greater among pups previously exposed to the odor than pups with no odor experience. Similarly, latency to attach to the nipple in the presence of the odor was lower among odor-preexposed pups, especially when odor exposure began within an hour of cesarean delivery. Odor exposure immediately after birth for just 15 minutes was sufficient to increase motor activity and to decrease latency to attach to a similarly scented surrogate nipple. These results suggest that olfactory experience very soon after birth can shape subsequent olfactory responses. The relative importance of the dearth of postnatal experience or of elevated neurochemicals immediately after birth and possible associative mechanisms underlying this learning is discussed.

Olfactory learning in the rat immediately after birth: Unique salience of first odors

“…These heating chambers were maintained at 35°C ± 1°C. Within the heating chamber, pups were placed into a hexagonal shaped shallow cup (8.5 mm wide at the top, 5.5 mm wide at the bottom, 2 mm deep) lined with synthetic fur (for a schematic depiction see Miller & Spear, 2008). All conditions had two pups in each cup, one male and one female.…”

“…One purpose of the current experiments was to extend the findings of Miller & Spear (2008) by further characterizing the features of olfactory learning in the hours just after birth. Experiment 1 tested the effects of multiple odor exposures on later odor-evoked motor activity.…”

“…Postnatal age (in hours) at odor exposure was manipulated (Miller & Spear, 2008). Rat pups were exposed to an odor immediately, one hour, or two hours after cesarean delivery to study the effects this might have on later attachment to a surrogate nipple scented with that same odor and behavioral activation in its presence.…”

Interactive Contributions of Genes and Early Experience to Behavioral Development

“…However, that is all that is known. Olfactory imprinting occurs in many mammalian species, including rodents (Miller & Spear, 2008), rabbits (Patris, Ferrier, Schaal, & Coureaud, 2008;Serra &Nowak, 2008) andhumans (e.g., Schaal, Hummel, &Soussignan, 2004) but much more research needs to be done.…”

Perinatal undernourishment and handling: effects on olfactory discrimination in the newborn rat

“…This activity is initially mediated by the maternal care and thereafter by nest environmental odors that induce important basic structural and functional plasticity for the pup's learning. 5,[11][12][13][14] Several studies have developed the reliable crosshabituation paradigm to test odor discrimination in immature animals by using the heart beat response, where a novel odor is presented repeatedly to habituate the heart beat odor responses; then, a second novel odor exposure (cross-habituation) induces a heart beat odor response as a sign of odor discrimination to a new odor. 8,15 The reliability of this learning paradigm is based on the high sensitivity of heart rate at neonatal ages to chemosensory cues.…”