A thalamo-cortico-amygdala pathway mediates auditory fear conditioning in the intact brain

Eur J Neurosci. 2006 Aug;24(3):894-900. doi: 10.1111/j.1460-9568.2006.04965.x.


The neural substrates of fear conditioning in rats have been well characterized, with converging lines of evidence indicating that conditioned stimulus (CS) and unconditioned stimulus (US) information form a CS-US association in the amygdala. Auditory CS information can reach the amygdala via two routes: a direct thalamo-amygdala pathway, and an indirect thalamo-cortico-amygdala pathway. Although either pathway can fully support learning when the alternate pathway is disrupted, many studies to date have argued that the thalamo-amygdala pathway is the principal auditory CS pathway in intact brains. To test this hypothesis, we trained rats in auditory fear conditioning, and 24 h later lesioned either pathway, leaving the alternate pathway intact. Later, animals were tested for conditioned freezing to the auditory CS. We report that lesions of the thalamo-amygdala pathway produced severe but incomplete deficits in freezing during the tone retention test, while lesions of the thalamo-cortico-amygdala pathway completely abolished freezing during tone presentation. These results suggest that the thalamo-cortico-amygdala pathway is the principal auditory CS pathway when the brain is intact.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acoustic Stimulation
  • Amygdala / anatomy & histology
  • Amygdala / physiology
  • Animals
  • Auditory Cortex / anatomy & histology
  • Auditory Cortex / physiology
  • Auditory Perception / physiology*
  • Conditioning, Psychological / physiology*
  • Denervation
  • Fear / physiology*
  • Geniculate Bodies / anatomy & histology
  • Geniculate Bodies / physiology
  • Male
  • Neural Pathways / anatomy & histology
  • Neural Pathways / physiology*
  • Prosencephalon / anatomy & histology
  • Prosencephalon / physiology*
  • Rats
  • Rats, Sprague-Dawley