Martina, I believe both the typical and atypical anti-psychotics act to reduce dopamine function in the brain. The atypicals have fewer seriouis side effects (such as tardive dyskinesia) than the older drugs, although they are more likely to result in weight gain. Both types of drug are most effective against the positive symptoms of schizophrenia. It is thought that the atypicals may also offer some benefit for the negative symptoms. If dopamine function is blocked too much, patients may become depressed/dysphoric (even more so), so it is a delicate balance of giving enough drug to manage the hallucinations etc. but not too much so as not to cause depression and contribute to even worse negative type symptoms. That is my understanding at least. Does that match with what your doctor has told you?

I think this article is pretty good:
http://emedicine.medscape.com/article/288259-treatment