Enduring effects of infant memories: infant odor-shock conditioning attenuates amygdala activity and adult fear conditioning.
ABSTRACT Early life adverse experience alters adult emotional and cognitive development. Here we assess early life learning about adverse experience and its consequences on adult fear conditioning and amygdala activity.
Neonatal rats were conditioned daily from 8-12 days-old with paired odor (conditioned stimulus, CS) .5mA shock, unpaired, odor-only, or naive (no infant conditioning). In adulthood, each infant training group was divided into three adult training groups: paired, unpaired or odor-only, using either the same infant CS odor, or a novel adult CS odor without or with the infant CS present as context. Adults were cue tested for freezing (odor in novel environment), with amygdala (14)C 2-DG autoradiography and electrophysiology assessment.
Infant paired odor-shock conditioning attenuated adult fear conditioning, but only if the same infant CS odor was used. The (14)C 2-DG activity correlated with infant paired odor-shock conditioning produced attenuated amygdala but heightened olfactory bulb activity. Electrophysiological amygdala assessment further suggests early experience causes changes in amygdala processing as revealed by increased paired-pulse facilitation in adulthood.
This suggests some enduring effects of early life adversity (shock) are under CS control and dependent upon learning for their impact on later adult fear learning.
Article: Postnatal exposure to synthetic predator odor (TMT) induces quantitative modification in fear-related behaviors during adulthood without change in corticosterone levels.[show abstract] [hide abstract]
ABSTRACT: Environmental stimuli and adverse experiences in early life may result in behavioral and physiological changes in adulthood. In several animal species, the odors cues are crucial in the setting of adaptive behaviors, especially towards predators. However, little is known about the effects of postnatal exposure to predator odor on the later physiological and behavioral responses to this natural stressor. Thus, the aim of this study was to investigate the effects of a postnatal exposure to synthetic predator odor (TMT) in mice pups on later adult fear-related behaviors and corticosterone levels in response to this specific stimulus. Pups postnatally exposed to only water showed later in adult life behavioral responses when exposed to TMT that were statistically different from mice that were exposed as neonates to TMT. In addition, mice exposed as neonates to TMT showed a decrease of fear-related behaviors while no differences occurred in the corticosterone levels between both groups.Behavioural brain research 12/2010; 215(1):58-62. · 3.22 Impact Factor