bump!

Looks like we'll have to start over... The belly laugh's on us
So why do we need this midget-size nest of neurons? One brain can do enough damage, after all. Remember the cartoon showing two sponges at the sea floor, wondering what to do next (up on shore, World War III had just roasted the landscape to a glowing cinder). And the yellow sponge said to the brown sponge, "Looks like we'll have to start over... But this time, no brains."

The sponges had a point -- why bother with two brains?

Convenience.

But this time, no brains.The advantage of having a gut brain to take responsibility for things digestive is two-fold: first, it is very close to the structures it must control, allowing what Jackie Wood of Ohio State University calls "second-to-second control." And second, it obviates the need for a thick cable of nerves to link the skull-brain to the gut-brain.

But is it really a brain in the first place?
That depends on what you mean by brain. People tend to use the term rather loosely -- remember the insistence on calling those early room-size computers "electronic brains?"

Seriously, what can the enteric nervous system actually do? At the least, it can evaluate situations based on sensory input, and come up with conclusions about how the digestive tract can best contribute to the animal's survival. That's the kind of processing that nerves in your eye or ear simply can't do.

And the enteric nervous system seems trainable, at least so its champions claim. In other words, it can learn. Evidence for this strange proposition comes from Hirschsprung's disease, a genetic defect which deprives the last portion of the colon, near the anus, of nerves. And without these nerves, the patient can't defecate. But Wood says that a German surgeon has successfully removed the defective portion of the colon from 300 patients, and attached the adjacent piece of colon to the anus.

This piece of plumbing knows nothing about toilets, having lived its life further upstream, so to speak. But within 18 months, it "learns" to go to the bathroom, indicating that the nerves have "learned" a new job.

Not bad for a "brain" that nobody even recognized 30 years ago.

What's your upstairs brain think of mad scientists?
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NISE/NSF

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