vetusvates
Gamaliel's Principle
I thought this article was very interesting. It talks about the circuitous feedback mechanisms that tie emotions and facial expressions together.
http://scienceblogs.com/neurophilosophy/2010/04/botox_may_diminish_the_experience_of_emotions.php
http://scienceblogs.com/neurophilosophy/2010/04/botox_may_diminish_the_experience_of_emotions.php