Amygdala central nucleus lesions attenuate acoustic startle stimulus-evoked heart rate changes in rats.
Amygdala central nucleus (CNA) lesions were used to test the hypothesis that stimulus-evoked heart rate changes can reflect the development of fear during acoustic startle testing. A 120-dB white noise startle stimulus produced freezing as well as phasic heart rate accelerations and decelerations, and an abrupt decrease in tonic heart rate, in sham-operated rats. These responses were all significantly reduced in CNA-lesioned rats. In contrast, an 87-dB stimulus elicited only significant phasic decelerations that were similarly attenuated by the CNA lesions. In a follow-up experiment, the CNA lesions also attenuated phasic cardiac decelerations evoked by a conditioned stimulus-like, 85-dB pure tone. The results support the contention (B. J. Young & R.N. Leaton, 1994) that heart rate changes can reflect fear conditioned during acoustic startle testing and, in addition, suggest that the amygdala mediates responses to nonsignal acoustic stimuli.
Young
B J
BJ
Department of Psychology, Dartmouth College. byoung@otago.ac.nz
Leaton
R N
RN
D000161:Acoustic Stimulation; D000679:Amygdala / Q000502:physiology*; D000818:Animals; D001143:Arousal / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping; D003214:Conditioning, Classical / Q000502:physiology*; D004292:Dominance, Cerebral / Q000502:physiology; D005239:Fear / Q000502:physiology*; D006185:Habituation, Psychophysiologic / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D051381:Rats; D013216:Reflex, Startle / Q000502:physiology*