Authors:

MURPHY, F.C., & Lawrence, A.D

Reference:

Year of publication:

2004

CBU number:

5902

Abstract:

Several classes of threat have been proposed on the basis of evolutionary arguments and the existence of specific phobias: predator threats (e.g. snakes); social threats (e.g. menacing humans); and physical/object threats (e.g. lightening). While it is now accepted that the amygdala plays an important role in processing emotional stimuli, and perhaps threatening stimuli in particular, the extent to which the amygdala is involved in processing different forms of threat remains unclear. Whereas theoretical models that consider the amygdala as a general ‘threat detector’ might predict similar levels of amygdala activity to different forms of threat, recent studies conducted in non-human primates suggest that the amygdala may be critical for detecting some threats but not others. We used fMRI to test these two competing theories of amygdala function. In a block design, thirteen healthy volunteers viewed three different forms of threat images (animal threats, social threats, and natural threats), each with its own neutral control condition and a low-level fixation baseline. Preliminary analyses confirmed significant amygdala activity in response to both social and natural threats, relative to their respective neutral baseline conditions. While no significant amygdala activity was found for animal threat images relative to matched neutral images, this may be due to significant amygdala activity found for the matched animal neutral images, relative to the low-level baseline. The implications of these findings for the above and other theories of the amygdala will be considered.