Gut feelings

It is a bit over-the-top to refer to "The second brain in our stomachs" as the BBC article titles the "network of neurons that line your stomach and your gut". I suppose you could call the network a "dedicated I/O processor" since it is ultimately responsible for deciding what to digest and what to hurl. Different parts of the network watch for different things.

It wouldn't do to have just one or two neurons monitoring "stretch", you need them all over the place and their output needs to be coordinated to give a final value of "I'm empty", "I'm a little full", "I'm very full", or "I've got an odd lump of something in here."

In addition, different parts of the gut produce different hormones. That sort of communication might as well be done locally, and the results sent to the brain; so in that sense there is some local "intelligence" in the network.

And we've been learning that intestinal flora either directly secrete hormones that effect us or that stimulate the gut to secrete them (I'm not sure if they have been able to distinguish the two possibilities), and at UCLA researchers say that consuming probiotics changed brain activity. It isn't clear what the significance of that was.

During the resting brain scan, the women consuming probiotics showed greater connectivity between a key brainstem region known as the periaqueductal grey and cognition-associated areas of the prefrontal cortex. The women who ate no product at all, on the other hand, showed greater connectivity of the periaqueductal grey to emotion- and sensation-related regions, while the group consuming the non-probiotic dairy product showed results in between.

Unfortunately I don't have access to the GastroJournal report, so I can't get a sense of how good their results were. There were only 12 women in each group, and reading brain scans without knowing what you are looking for sounds like a fruitful source of false positives. So I'm dubious, but willing to be convinced: We're full of surprises. But even if there are changes, it would still have to be proven that they are due to the bacteria.