title: A thalamo-cortico-amygdala pathway mediates auditory fear conditioning in the intact brain.
abstract: 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.
authors.affiliation: Department of Psychology, 335 Guthrie Hall, University of Washington, Seattle, WA 98195-1525, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Boatman
authors.forename: Jeansok J
authors.initials: JJ
authors.lastname: Kim
mesh_terms: D000161:Acoustic Stimulation; D000679:Amygdala / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D001303:Auditory Cortex / Q000033:anatomy & histology / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology*; D003714:Denervation; D005239:Fear / Q000502:physiology*; D005829:Geniculate Bodies / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology*; D016548:Prosencephalon / Q000033:anatomy & histology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley