In the spring, Neurophilosophy had a post on the research of D. Havas into the effects of botox on emotion. (here).

Do you smile because you’re happy, or are you happy because you are smiling? Darwin believed that facial expressions are indeed important for experiencing emotions…Botox, which is used by millions of people every year to reduce wrinkles and frown lines on the forehead, works by paralyzing the muscles involved in producing facial expressions…it impairs the ability to process the emotional content of language, and may diminish the quality of emotional experiences…

Havas recruited 40 women for the new study, all of whom were seeking first-time botox injections as a cosmetic treatment for frown lines on the forehead. These participants were asked to read sentences describing happy, sad or emotionally neutral situations. Immediately afterwards, they were taken to the physician, who gave them a single injection of botox into the corrugator supercilii, or “frown” muscle. (Botox acts by inhibiting the release of the neurotransmitter acetylcholine from motor neurons, leading to temporary muscle paralysis 24-48 hours later. Typically, the procedure is repeated after 3-4 months; with time, the muscles may atrophy, or waste away, through disuse.) Two weeks after the injection, the participants returned to lab to read another set of similar sentences.

The reseachers found that botox slowed the reading of the sentences containing sad emotional content, which, as the earlier work showed, would normally cause the frown muscle to contract. The reading time for the happy and neutral sentence was the same in both sessions. The researchers assume that the increase in reading time means that paralysis of the frown muscles hindered the participants’ understanding of the emotional content of the sad sentences. They also argue that their findings support the hypothesis that feedback from the muscles involved in producing facial expressions is critical in regulating emotional experiences.

…news stories completely overlook the more profound implication of the results - that by paralyzing the muscles involved in producing facial expressions, botox may actually diminish the experience of emotion in those who use it.

This is another piece of evidence that consciousness is primarily concerned by perception. In this case it is registering an emotional state primarily from the perception of movement of facial muscles.