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| http://www.scientificamerican.com/article.cfm?id=the-neuroscience-of-gut | 
   I found this part interesting:
"Regardless of how these intestinal “guests” exert their influence, these  studies suggest that brain-directed behaviors, which influence the  manner in which animals interact with the external world, may be deeply  influenced by that animal’s relationship with the microbial organisms  living in its gut. And the discovery that gut bacteria exert their  influence on the brain within a discrete developmental stage may have  important implications for developmental brain disorders." 
