The Role of TMS in Studying Facial Signals

Article:
“Dissociable roles of the human somatosensory and superior temporal cortices for processing social face signals”

Authors: Gilles Pourtois, David Sander, Michael Andres, Didier Grandjean, Lionel Reveret, Etienne Olivier and Patrik Vuilleumier

Published by: EuropeanJournalofNeuroscience,Vol.20,pp.3507–3515,2004

This article examines the role of the right somatosensory cortex and the right superior lateral temporal cortex in recognizing emotional expression, either fear or happiness, and shift in eye gaze. The researchers used single pulse transcranial magnetic stimulation over these two areas of the brain while participants completed the given task. The participants, who were all healthy, had to look at two successive pictures depicting people with different emotions and directions of eye gaze. They were then asked to press a button indicating whether the two pictures showed the same emotion and the same eye gaze. The pictures only showed people displaying happy or fearful emotions and eye gazes were only shifted either direction by 30 degrees.
The results concluded that TMS over the somatosensory areas interfered with recognizing fear and that TMS over the superior temporal cortex interfered with the perception of gaze shifts, meaning that the two different areas in the brain have unique functions. The experiments also found that TMS slowed down recognition of fearful expressions versus recognition of happy expressions. I thought this was a very interesting finding. The article suggests that happiness is easier to detect because it can be identified by one universal facial signal, a smile.
After reading the article, I wonder why the researchers chose to test these two emotions, as opposed to “opposite” emotions like happiness and sadness. I also wonder how TMS would affect the recognition of other emotions, especially anger, since I think that is very easy to detect. I also found it interesting that the two successive pictures were always different genders. What is it about the differing genders that the researchers were looking for? This makes me question whether being able to identify with the person on the picture may have something to do with recognition of social cues. Perhaps if the participant knew the person in the picture the results would change. The most interesting concept for me was that recognizing fear in other people uses a different part of the brain (somatosensory areas) than recognizing and responding to fear in one’s self, which we have learned involves using the amygdala.