The circus of the Society of Neuroscience meeting is upon us. San Diego, with no residual smell of burning in the air. I’m milling around the cavernous conference centre – actually one of the more attractive ones of this size – with over 30,000 other delegates, wondering how to choose between the parallel sessions. But there’s a feeling of famine rather than plenty – the awareness of just how much you are missing by going to one particular session.

One of the coolest things I heard today was about the non-uniformity of responsiveness of serotonergic neurons in the raphe nucleus, which is in the brain stem, the most primitive part of the brain.

Nearly all serotonin-releasing neurons in the brain emerge from this nucleus. These neurons have been implicated in all sorts of pathological behaviours – depression, aggression, obsessive-compulsive disorder, eating disorders.

You wonder how serotonin is able to control so many diverse behaviours, but you don’t really expect to find the answer in the brains stem, Zachary Mainen from Cold Spring Harbor Laboratory told me. So when he started to do single cell recordings from individual neurons in the raphe nucleus in mice performing a complex behaviour test, he expected to see each of them firing in the same, signature way – no matter whether the mouse was making a decision, searching for a reward, drinking, or just moving. But it wasn;t the case. He found different neurons responded quite independently to the different behaviours.

So cells right down deep in the unsophisticated brain stem, from where it is difficult to record, are possibly tuned for a limited range of tasks. Cool.

The circus of the Society of Neuroscience meeting is upon us. San Diego, with no residual smell of burning in the air. I’m milling around the cavernous conference centre – actually one of the more attractive ones of this size – with over 30,000 other delegates, wondering how to choose between the parallel sessions. But there’s a feeling of famine rather than plenty – the awareness of just how much you are missing by going to one particular session.

One of the coolest things I heard today was about the non-uniformity of responsiveness of serotonergic neurons in the raphe nucleus, which is in the brain stem, the most primitive part of the brain.

Nearly all serotonin-releasing neurons in the brain emerge from this nucleus. These neurons have been implicated in all sorts of pathological behaviours – depression, aggression, obsessive-compulsive disorder, eating disorders.

You wonder how serotonin is able to control so many diverse behaviours, but you don’t really expect to find the answer in the brains stem, Zachary Mainen from Cold Spring Harbor Laboratory told me. So when he started to do single cell recordings from individual neurons in the raphe nucleus in mice performing a complex behaviour test, he expected to see each of them firing in the same, signature way – no matter whether the mouse was making a decision, searching for a reward, drinking, or just moving. But it wasn;t the case. He found different neurons responded quite independently to the different behaviours.

So cells right down deep in the unsophisticated brain stem, from where it is difficult to record, are possibly tuned for a limited range of tasks. Cool.