title: Response characteristics of neurons in the medial component of the medial geniculate nucleus during Pavlovian differential fear conditioning in rabbits.
abstract: Recent evidence suggests that the amygdaloid central nucleus (ACE) may contribute significantly to Pavlovian fear-conditioned bradycardic responses during the presentation of conditioned emotional stimuli. Because the medial component of the medial geniculate nucleus (MGm) is a major source of input to the region of the ACE, the extracellular single-unit responses of MGm neurons were examined during Pavlovian differentially conditioned bradycardic responding in rabbits. Conditioning involved pairing one tone (CS+) with paraorbital shock and presenting another tone (CS-) in the absence of shock. Two general classes of MGm neurons were identified based on their conditioned-response characteristics. Both groups responded differentially to the CSs. One group responded with greater increases in activity and at a shorter latency to the CS+ compared with the CS-, whereas the other group responded with greater increases in activity and at a shorter latency to the CS- compared with the CS+. Recordings from MGm neurons in naive rabbits prior to conditioning provided evidence that the acoustic stimuli used subsequently as the CS+ and CS- did not evoke differential responses. These results suggest that the MGm along with the ACE may be forebrain components of a neural circuit involved in the acquisition and/or expression of Pavlovian fear-conditioned bradycardic responses.
authors.affiliation: Department of Psychology, University of Vermont, Burlington 05405-0134.
authors.forename: W F
authors.initials: WF
authors.lastname: Supple
authors.forename: B S
authors.initials: BS
authors.lastname: Kapp
mesh_terms: D000679:Amygdala / Q000502:physiology; D000818:Animals; D001143:Arousal / Q000502:physiology*; D001931:Brain Mapping; D003215:Conditioning, Eyelid / Q000502:physiology*; D005239:Fear / Q000502:physiology*; D005829:Geniculate Bodies / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology; D011817:Rabbits; D011930:Reaction Time / Q000502:physiology