I’ve got a gut feeling this could be an influential study…

So, it turns out that you really do listen to your gut. Rather literally, as it turns out. It’s been known for a long time that your viscera, i.e., your guts, have signalling properties that communicate with the brain. This has been a perennial source of interest, because there are lots of theories all the way from nineteenth-century philosopher William James to modern neuroscientist Antonio Damasio that our brains construct our lived moment-to-moment experience by integrating inputs from multiple body systems, making the world of our thoughts, emotions, and decision-making intimately dependent on not only our mentation, but on the state of our whole body.

Now a group of Japanese researchers led by T. Hashimoto has published a study in the journal Neuroscience in which they may have identified which part of the brain receives the most direct input from the guts. They used a technique called electrointestinography (EIG; see the word “intestine” buried in the middle of all that Greek?), which is really just like the electroencephalography (EEG) that’s near and dear to our hearts at Choratech, except that it records electrical activity from sensors placed on the abdomen, over the intestines, rather than on the scalp, over the brain. The researchers measured the oscillatory patterns of the electrical signals that were coming from the intestines, and their research subjects also just happened to be lying in an MRI scanner (what luck!), so they could correlate rising and falling activity in the guts with the rising and falling activity in the brain.

AntInsThey found that the gut activity correlated with activity in the brain region called the insula (lit. Latin, “island”). This structure is invisible from the outside of the brain, because it’s buried underneath the bottom part of the frontal and parietal lobes, and the top part of the temporal lobes. The insula is intimately associated with detecting motivationally significant information in both the external and internal (bodily) environments, and passing that information along so it can influence decision-making and behaviour. The authors found that the gut activity correlated most closely with regions of the insula on the right side, in the middle and at the front, as shown in the accompanying image taken from their study.

Interestingly, those with the most gut activity were also those with the highest self-reported anxiety. The authors also showed significant relationships between anxiety scores and the linkage between the right insula and related structures (the left insula and the dorsal anterior cingulate), also known to be involved with the experience of anxiety.

We have a thousand colloquial expressions that suggest that our “gut” has input into our decision-making; I’m sure you can think of two or three right off the top of your head. It seems to be turning out that this isn’t just metaphor: our actual, physical gut does indeed have this type of influence, and that its gateway to the brain is somewhere in the middle and front of the right insula.

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