Hiccups help baby brain development

Hiccups are uncomfortable and always seem to happen at the worst times. And there’s not a clear explanation yet for why we have them - they’re involuntary spasms of the diaphragm that don’t seem to have a purpose. But new evidence shows that for babies, hiccups might actually help their brains develop - meaning adults might get them as a relic from our infancy, when they were genuinely useful. UCL scientists suggested this after looking at thirteen babies, who happened to be hiccuping while their brains were being scanned for other studies. They found spikes of brain activity that they think help the babies figure out which parts of their bodies are which. Phil Sansom got the full story from lead author Kim Whitehead…

Kim - So what we found is that when infants have a hiccup, they have a large change in brain activity immediately after the hiccup.

Phil - Is that them sensing their own hiccup, basically?

Kim - The way that we would interpret it, yes, is that the information from the feel of the diaphragm muscle contracting and potentially the sound that the hiccup makes, the 'hic' noise, is reaching the brain and being processed by the brain, by these young babies. And because we have a little sensor on their belly as part of our setup, we were able to look at the brain activity in real time.

Phil - Did you have to wait a while for them to hiccup? Because am I right that babies are quite big hiccupers, right?

Kim - Exactly. It all relies on the fact that babies are big hiccupers. This was a retrospective analysis, we started to become interested in it, and I realised that some of the babies hiccuped by chance spontaneously during recordings that were being acquired for other scientific questions. And because they hiccup so often - so they hiccup about 1 percent of the day - just by chance we will capture some of these hiccups during our experimental protocol.

Phil - Got it. So you've got your babies with the sensor on their chest. But how do you measure what's going on in their brains?

Kim - So we use a technique called EEG, and it stands for electro-encephalopathy. And basically it's able to record the ongoing electrical activity in the brain. The EEG is completely painless, we can record it from the scalp with the little sensors, and the great thing about it is that it allows us to see brain activity change millisecond by millisecond, so that's the level of a thousandth of a second. So we see three separate brainwaves that look quite distinct. And what we've seen from other aspects of our research is that when the brain processes sensory information, it wants to get multiple parts of information. So for example it might want to process where in the body that came from. And then those later brainwaves are still a source of a lot of research interest, but they're potentially about extra-sensory information. So, "are other things happening at the same time as this sensory input that we're receiving? What other aspects can we classify in the brain?"

Phil - And then what are the consequences of big spikes in brain activity when you're hiccupping, for a baby?

Kim - So we know that brain activity is correlated with different outcomes, for example, in the milestones at school. But that's really just a correlation, so with human data it's difficult to prove what is causally related to brain development. But based on people who work with animal models of development in early life, they suggest that these really big brain waves that are very typical of the early life period help to strengthen sensory networks in the brain, at a time when the brain is just starting to establish those networks I was talking about. We have a network for touch, a network for motor control, etc. And it's useful for the immature brain to have a huge brainwave, where lots of brain cells get activated at the same time by a sensory stimulus, because it helps them to link up an experience that happens at the body surface - or the muscles of the body - helps to link that with brain pathways. And we all need that, as we grow up, in order to be aware of our surroundings, be able to interpret sensory signals.

Phil - So the hiccups might be really good for the developing baby brain?

Kim - We think that they may have a role in the developing baby brain, exactly.