The limbic system is the emotional center of the brain and also is tied to smell, motivation and memory. This system was evolved from a primitive system dedicated to smell that was linked to survival behaviors in early mammals. How interesting that the part of our brains that is responsible for our feelings was first the spot dedicated to smell. It makes sense that smell is tied to memory, we've all had times when we've caught a wiff of a particular scent and had a strong memory pulled into focus but I had no idea how emotional the power of smell could be.
A associate psychiatry professor at the University of Pennsylvania conducted a study where he compared the size of olfactory bulbs in people with and without schizophrenia.
"On average, the bulb sizes of schizophrenic subjects were 23 percent smaller than those of subjects in a control group. These findings not only concentrate on an area of the brain previously ignored in schizophrenia studies, but, according to Turetsky, they also offer a biological basis to his earlier findings that people suffering from the disease were abnormal in their ability to smell." - http://www.psychologytoday.com/articles/200009/the-emotional-power-smell
If they were able to replicate these findings and find causation (not JUST correlation) that could be a huge breakthrough in the treatment for schizophrenia.
Here is a (simple) picture of the olfactory bulbs and limbic system!