Enduring effects of infant memories: infant odor-shock conditioning attenuates amygdala activity and adult fear conditioning.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Sevelinges
Yannick
Y
Institut des Sciences Cognitives, Université Claude Bernard Lyon 1, France.
Moriceau
Stephanie
S
Holman
Parker
P
Miner
Cathrine
C
Muzny
Kyle
K
Gervais
Remi
R
Mouly
Anne-Marie
AM
Sullivan
Regina M
RM
D000375:Aging; D000679:Amygdala / Q000000981:diagnostic imaging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography / Q000379:methods; D001362:Avoidance Learning; D001522:Behavior, Animal; D003214:Conditioning, Classical / Q000502:physiology*; D003847:Deoxyglucose / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000528:radiation effects; D005239:Fear; D046352:Freezing Reaction, Cataleptic / Q000502:physiology; D008297:Male; D018782:Maze Learning; D008568:Memory / Q000502:physiology*; D009812:Odorants; D009830:Olfactory Bulb / Q000000981:diagnostic imaging; D011859:Radiography; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects