juliet

I thought ulcers were caused by Helicobacter pylori, for which the researchers won a Nobel prize last year? Could be wrong though - I don't know anything about the GI system.

Re the serotonin stuff... One reads lots of attempts to explain behaviour in terms of whole-brain levels of neurotransmitters, and for two main reason - you can change neurotransmitter levels with drugs, which is something there is a lot of money and interest in doing, and it's relatively easy to explain. The other way to explain behaviour is in terms of neural network type models, but there's not quite so much money in that and far fewer people can understand the research (I tried and failed). The two extremes are appropriate in different areas, I guess - IMHO it would be silly to try and explain behaviour in terms of whole-brain glutamate levels, for example, as glutaminergic neurons are everywhere, while conversely there are two pretty clear dopaminergic pathways in the brain so it's more plausible that they might have specific functions. But I've never been sure what the evidence is - and this is probably just my ignorance as I did very little pharmacology - that there is a functional serotonergic system rather than just lots of different unconnected effects happening at once.