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· 9 July 2010 ·

Fear, Faces and the Amygdala

Brain imaging techniques such as CT, fMRI and EEG have revolutionised psychology. They are indeed exciting technologies that can offer insights into the way our brain works. And thus, scientific columns in newspapers regularly report that a behaviour or perception can be linked to a certain brain area. The idea is that if we know that if a brain area is active during a certain task that is otherwise not, it is involved in the process, or, if a brain area is defective and with it specific cognitive functions, then these are linked, too. But things are not as simple. (They never are) Just because an area is active during a cognitive process does not necessarily tell you what it actually does.

Thus, it was generally assumed that the amygdala was involved in the processing of fear and threat. When psychologists made participants observe fearful faces in an fMRI, the amygdala would light up. So the evidence clearly points out that the amygdala is processing fearful faces, isn’t it? Further evidence that the processing of fearful faces is directly linked to the amygdala seemed to be provided by the case of SM, a patient with a lesion in the amygdala, who showed an impairment in recognising fear in facial expressions. Thus, when SM was presented with a number of fearful and happy faces she was able to recognise the happy ones only, and had difficulties identifying faces expressing fear. Therefore, the case of SM seemed to provide considerable support to the hypothesis that the amygdala was involved in the processing of fearful faces. Case sorted, right?

Not quite so. Adolphs et al. (2005) investigated the case further. In faces, fear is primarily expressed in the eye region, and happiness in the area of the mouth. (smile!) Thus, when you want to tell if someone is scared you have to look at her eyes, if you want to know whether someone is happy, you should watch out for a smile. So Adolphs and colleques asked SM to specifically look at the eye region when trying to tell the emotional state of a face. And suddenly SM’s fear peception in faces was equal to that of normal people, who did not show an impairment in the amygdala. So the evidence suggests that the amygdala is not directly linked to fear processing, but rather seeks, and makes use of, information in the eye region of faces.

The lessons learnt from this and similar cases is, that although brain imaging technology provides useful insights into cognitive processes, we have to remain cautious about their interpretation. The data provided by brain imaging is correlational only, and it is very difficult to draw causal connections to what certain brain areas are actually processing.

This text was inspired by a talk by Philippe Schyns at the Mind Science and Everything Conference 2010.

For further reading, please refer to the following papers:
Adolphs, R., Gosselin, F., Buchanan, T.W., Tranel, D., Schyns, P., & Damasio, A.R. (2005), A mechanism for impaired fear recognition after amygdala damage, Nature 433, 68-72 | DOI:10.1038/nature03086

Adolphs, R, (2008) Fear, faces, and the human amygdala, Current Opinion in Neurobiology, 18 (2), Pages 166-172 | DOI:10.1016/j.conb.2008.06.006

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