The Basolateral Amygdala is critical for learning about neutral stimuli in the presence of danger, and the perirhinal cortex is critical in the absence of danger

N. M. Holmes, S. L. Parkes, A. S. Killcross, R. F. Westbrook
Journal of Neuroscience. 2013-08-07; 33(32): 13112-13125
DOI: 10.1523/JNEUROSCI.1998-13.2013

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1. J Neurosci. 2013 Aug 7;33(32):13112-25. doi: 10.1523/JNEUROSCI.1998-13.2013.

The basolateral amygdala is critical for learning about neutral stimuli in the
presence of danger, and the perirhinal cortex is critical in the absence of
danger.

Holmes NM(1), Parkes SL, Killcross AS, Westbrook RF.

Author information:
(1)School of Psychology, University of New South Wales, Sydney 2052, New South
Wales, Australia.

The perirhinal cortex (PRh) and basolateral amygdala (BLA) appear to mediate
distinct aspects of learning and memory. Here, we used rats to investigate the
involvement of the PRh and BLA in acquisition and extinction of associations
between two different environmental stimuli (e.g., a tone and a light) in
higher-order conditioning. When both stimuli were neutral, infusion of the GABAA,
muscimol, or the NMDA receptor (NMDAR) antagonist ifenprodil into the PRh
impaired associative formation. However, when one stimulus was neutral and the
other was a learned danger signal, acquisition and extinction of the association
between them was unaffected by manipulations targeting the PRh. Temporary
inactivation of the BLA had the opposite effect: formation and extinction of an
association between two stimuli was spared when both stimuli were neutral, but
impaired when one stimulus was a learned danger signal. Subsequent experiments
showed that the experience of fear per se shifts processing of an association
between neutral stimuli from the PRh to the BLA. When training was conducted in a
dangerous environment, formation and extinction of an association between neutral
stimuli was impaired by BLA inactivation or NMDAR blockade in this region, but
was unaffected by PRh inactivation. These double dissociations in the roles of
the PRh and BLA in learning under different stimulus and environmental conditions
imply that fear-induced activation of the amygdala changes how the brain
processes sensory stimuli. Harmless stimuli are treated as potentially harmful,
resulting in a shift from cortical to subcortical processing in the BLA.

DOI: 10.1523/JNEUROSCI.1998-13.2013
PMID: 23926265 [Indexed for MEDLINE]


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