The basolateral amygdala is critical for the acquisition and extinction of associations between a neutral stimulus and a learned danger signal but not between two neutral stimuli
Journal of Neuroscience. 2010-09-22; 30(38): 12608-12618
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1. J Neurosci. 2010 Sep 22;30(38):12608-18. doi: 10.1523/JNEUROSCI.2949-10.2010.
The basolateral amygdala is critical for the acquisition and extinction of
associations between a neutral stimulus and a learned danger signal but not
between two neutral stimuli.
Parkes SL(1), Westbrook RF.
(1)School of Psychology, University of New South Wales, Sydney, 2052 New South
We studied the neural substrates of higher-order conditioned fear in rats. We
first studied acquisition and extinction of second-order fear. One stimulus (S1)
was paired with a footshock unconditioned stimulus (US), a second stimulus (S2)
was paired with S1, and, finally, fear of S2 was extinguished by S2 alone
exposures. Reversible inactivation of the basolateral amygdala (BLA) via
muscimol, systemic injection of the NMDA receptor (NMDAr) antagonist MK-801
[(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate], or
intra-amygdala infusion of the NMDAr NR2B subunit selective antagonist ifenprodil
impaired both acquisition and extinction of fear to S2. We then studied
acquisition and extinction of sensory preconditioned fear. S2 was first paired
with S1, S1 was then paired with the US, and, finally, fear of S2 was
extinguished by S2 alone exposures. Extinction of sensory preconditioned fear was
impaired by a BLA infusion of muscimol or ifenprodil and by MK-801. Acquisition
of the S2-S1 association and extinction of this association by S2 alone exposures
before conditioning of S1 was impaired by MK-801 but not by a BLA infusion of
muscimol. These results show that NMDAr activation in the BLA is critical for
acquisition of second-order conditioned fear and for the extinction of both
second-order and sensory preconditioned fear just as it is for acquisition and
extinction of first-order conditioned fear. Acquisition and extinction of an
association between two neutral stimuli also require NMDAr activation. However,
the present results show that the acquisition and extinction of these
associations do not require the BLA.
PMID: 20861367 [Indexed for MEDLINE]