Amygdala-dependent and amygdala-independent pathways for contextual fear conditioning

Neuroscience. 2007 Jul 29;147(4):919-27. doi: 10.1016/j.neuroscience.2007.04.026. Epub 2007 Jun 22.


The basolateral amygdala (BLA), consisting of the lateral and basal nuclei, is considered to be essential for fear learning. Using a temporary inactivation technique, we found that rats could acquire a context-specific long-term fear memory without the BLA but only if intensive overtraining was used. BLA-inactivated rats' learning curves were characterized by slow learning that eventually achieved the same asymptotic performance as rats with the BLA functional. BLA inactivation abolished expression of overtrained fear when rats were overtrained with a functional BLA. However, BLA-inactivation had no effect on the expression of fear in rats that learned while the BLA was inactivated. These data suggest that there are primary and alternate pathways capable of mediating fear. Normally, learning is dominated by the more efficient primary pathway, which prevents learning in the alternate pathway. However, alternate pathways compensate when the dominant pathway is compromised.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amygdala / drug effects
  • Amygdala / physiology*
  • Analysis of Variance
  • Animals
  • Behavior, Animal
  • Conditioning, Classical / drug effects
  • Conditioning, Classical / physiology*
  • Fear*
  • Freezing Reaction, Cataleptic / drug effects
  • Freezing Reaction, Cataleptic / physiology
  • GABA Agonists / pharmacology
  • Male
  • Memory / drug effects
  • Memory / physiology
  • Muscimol / pharmacology
  • Neural Pathways / drug effects
  • Neural Pathways / physiology*
  • Rats
  • Rats, Long-Evans


  • GABA Agonists
  • Muscimol