| Program#/Poster#: |
603.04/EEE7 |
| Title: |
Infralimbic prefrontal
cortex suppresses amygdala-mediated fear reactions as a function of active
avoidance learning |
| Location: |
Hall F-J |
| Presentation Time: |
Tuesday, Oct 16, 2012,
11:00 AM -12:00 PM |
| Authors: |
*J. M. MOSCARELLO1,
J. E. LEDOUX1,2;
1Ctr. for Neural Sci., New York Univ., New York, NY; 2Emotional
Brain Inst., Nathan Kline Inst., Orangeburg, NY |
| Abstract: |
By gaining behavioral
control over an aversive unconditioned stimulus (US) animals can achieve
a strong reduction in the expression of learned fear. The central nucleus
of the amygdala (CE) has a demonstrated role in the production of conditioned
defensive behaviors, whereas the infralimbic prefrontal cortex (ilPFC) has
been shown to inhibit the output of aversive Pavlovian reactions. These
regions were examined in a rodent model of signaled active avoidance (SigAA)
behavior, in which rats learn to shuttle during conditioned stimulus (CS)
presentation to avoid an aversive US. Pre-training lesions of ilPFC attenuated
the acquisition of SigAA and potentiated freezing to the CS, whereas lesions
of CE produced contrasting effects by facilitating avoidance and reducing
conditioned freezing. Thus, CE underpins behaviors that oppose active avoidance,
whereas ilPFC suppresses conditioned fear as avoidance is acquired. Pharamacological
inactivation of ilPFC demonstrated its involvement in both the acquisition
and maintenance phases of SigAA learning, though inactivation during acquisition
produced longer lasting effects, which continued into subsequent drug free
sessions. Intriguingly, SigAA leads to a diminution of CS-evoked fear reactions
even when the cue is presented outside the training envionrment; ilPFC inactivation
prior to CS exposure in an alternate context prevented this effect. Finally,
injection of a protein synthesis inhibitor into ilPFC or CE impaired or
facilitated SigAA, respectively, suggesting that avoidance training produces
two opposing memory traces in these regions. These data support a model
in which avoidance learning recruits ilPFC to blunt the output of CE-mediated
fear reactions. Behavioral control over US presentation recruits ilPFC to
inhibit those Pavlovian defensive reactions that aggregate into conditioned
fear. |
| Support: |
NIH grant F32MH094061 |
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