Table 1.

Odor-Shock Conditioning in Rat Pups

Measure	Sensitive period (PN1–9)		Conditional sensitive period (PN10–15)
	Saline	CORT increase (systemic or intra-amygdala CORT)	Saline	CORT reduction (maternal presence, adrenalectomy, amygdala CORT receptor blocker)
Behavior	Preference	Aversion	Aversion	Preference
Corticosterone level	Low	High	High	Low
2-DG uptake
Olfactory bulb	Increase	No change	No change	Increase
Anterior piriform cortex	Increase	No change	No change	Increase
Posterior piriform cortex	No change	Increase	Increase	No change
Amygdala	No change	Increase	Increase	No change

Note. The table summarizes our understanding of the brain regions supporting sensitive period (PN1–9) odor preference learning and conditional sensitive period (PN10–15) odor aversion learning. Learned odor preferences during the sensitive period are associated with increased neural activity, as measured by 2-deoxyglucose uptake within the olfactory bulb and anterior piriform “olfactory” cortex. There is no significant activity within the amygdala or posterior piriform cortex. In contrast, when CORTis high endogenously (PN12) or via treatment (PN8), learned odor aversions are associated with significant activity within the amygdala and posterior piriform cortex. Maternal presence during odor-shock conditioning in PN12 pups decreases CORT levels, increases neural activity within the olfactory bulb and anterior piriform “olfactory” cortex, inhibits posterior piriform cortex and amygdala responsivity, and permits odor preference learning. Note, this is the same neural circuitry responsible for PN8 preference learning (Moriceau & Sullivan, 2006; Moriceau et al., 2006; Raineki, Shionoya, Sander, & Sullivan, 2009; Sullivan, Landers, et al., 2000). PN = postnatal day.