The nonhuman primate amygdala is necessary for the acquisition but not the retention of fear-potentiated startle.
BACKGROUND
In a previous study, we found that rhesus monkeys prepared with bilateral lesions of the amygdala failed to acquire fear-potentiated startle to a visual cue. However, a second group of monkeys, which received the lesion after training, successfully demonstrated fear-potentiated startle learned prior to the lesion.


METHODS
In the current experiment, the eight monkeys used in the second part of the original study, four of which had bilateral amygdala lesions and the four control animals, were trained using an auditory cue and tested in the fear-potentiated startle paradigm. This test was performed to determine whether they could acquire fear-potentiated startle to a new cue.


RESULTS
Monkeys with essentially complete damage to the amygdala (based on histological analysis) that had retained and expressed fear-potentiated startle to a visual cue learned before the lesion failed to acquire fear-potentiated startle to an auditory cue when training occurred after the lesion.


CONCLUSIONS
The results suggest that while the nonhuman primate amygdala is essential for the initial acquisition of fear conditioning, it does not appear to be necessary for the memory and expression of conditioned fear. These findings are discussed in relation to a network of connections between the amygdala and the orbitofrontal cortex that may subserve different component processes of fear conditioning.
Antoniadis
Elena A
EA
Department of Psychiatry and Behavioral Sciences, University of California, Davis, Davis, California, USA.
Winslow
James T
JT
Davis
Michael
M
Amaral
David G
DG
D000161:Acoustic Stimulation; D000679:Amygdala / Q000293:injuries / Q000473:pathology / Q000502:physiology*; D000818:Animals; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D005239:Fear / Q000502:physiology* / Q000523:psychology*; D007051:Ibotenic Acid / Q000633:toxicity; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D010775:Photic Stimulation; D013216:Reflex, Startle / Q000502:physiology*
D018690:Excitatory Amino Acid Agonists; D007051:Ibotenic Acid