3 things to know about this brain cap (or EEG, or electroencephalogram)

[By: Sayaka Fujita]

When visiting our babylab in Lancaster, some people say, “I’m here to do a study with a cap like a jellyfish”. Then I know they are here for my study. Yes, I use this jellyfish cap, called EEG (or electroencephalogram, to be more precise), to monitor baby’s brain activity.

A cap which monitors brain activity sounds cool – but what exactly does it do? When was it invented, by whom, and what can it tell us? In this month’s blog, I’ll talk about three things about EEG, as well as three reasons we should be bothered to measure brain activities despite all the challenges to get good data from cheeky little ones.

1. It was first invented in 1929.

In 1875, an English electrophysiologist Richard Caton reported that changes in body movement could influence the flow of electrical currents monitored by channels placed on the surface of the head of an animal (and also this is when they noticed electrical stimulation could affect bodily movement) [1]. Half a century later, in 1929, a German psychiatrist called Hans Berger placed electrodes on the human scalp, and successfully recorded a relatively slow and rhythmic brain waves [2]. This was considered the first discovery of human EEG. However, neurophysiologists at that time initially believed that such slow waves Berger observed was merely a noise or some sort. During 1930s, similar observations were reported by renowned physiologists, which led to the acceptance of the EEG as a “real” phenomenon.

Figure 1: EEG recording in 1947 [a].
The first EEG was a very coarse measure of brain activities, and it was long before computers became available for EEG analyses. So electrical signals needed to be translated into ink onto paper by hand. Furthermore, people whose brain activity was monitored had to lie down quietly, otherwise it would interfere with the data reading. Now that technology has advanced, collecting and analysing EEG is much easier in terms of cost and portability – they are relatively cheap compared to other brain imaging techniques such as fMRI, and the improvement in techniques and algorithms allows us to measure brain activities of a moving person like a marathon runner [3].

2. It monitors electricity in a brain, but it’s completely safe.

As previously mentioned, EEG monitors electricity in a brain. Your brain has a hundred of billions of brain nerve cells called neurons. They produce electrical signals to communicate information with each other, and EEG can detect activity of large groups of neurons in small areas of the brain, which are active at the same time. This then could be recorded in a wave pattern on a computer screen (or on a graph paper a long time ago). The waves would look like this:

Figure 2: EEG wave examples, which is produced using the authors’unpublished data only for illustrative purposes.

Detecting electricity in your head may sound scary but it really is not. EEG is a completely safe, non-invasive way of monitoring brain activities as EEG channels do not give out electricity (contrary to technique like transcranial magnetic stimulation, where [ [bit to rephrase] some current is sent]). The technique is so safe that it has long been used in hospitals for about 80 years, with the first clinical EEG laboratories being founded in the US in the 1930s and 40s. It has been particularly useful for patients with seizures and epilepsy because it is known that patients with epilepsy typically demonstrate characteristic EEG patterns during an epileptic seizure [4]. It has also been used to evaluate the depth of anaesthesia, and to confirm brain death [4,5].

3. We read waves to understand your brain.

The data collected by EEG looks like a wave, as I mentioned earlier. The waves comprise multiple dimensions, but for now let’s look at the frequencies, which is basically how fast the wave changes/varies. The unit is Hz, and higher Hz means faster waves (e.g. 10 Hz means 10 cycles of wave happens per second). We typically use a range of Hz to link a certain pattern of brain waves to a certain cognitive activity. For instance, Alpha waves (7-12Hz) are known to be prominent when you close your eyes and feel relaxed, but not asleep. Theta (4–7Hz) waves have been linked to several cognitive functions including memory [6].

However, it is important to emphasise that EEG does NOT measure your thoughts or feelings. So it cannot be used to read your mind. It only tells us whether there is something going on in your brain (which is why we can use this to confirm brain death), and whether the waves look different depending on what you are doing while your brain activity is being monitored.

So, that is the very basics about EEG. It sounds good and straightforward – Put the cap on and get the waves, and interpret the waves. But It won’t go that easy when you want to do this with young babies.

The principle is the same, but there needs to be some modifications to use this cap with small humans. For instance, the cap size obviously needs to be much smaller than adults’. But the biggest difference is how we could get good data.

Getting good data from these little ones is VERY challenging. Babies can be fussy, hungry and sleepy so they can’t sit still, which distort the data. Even though I said earlier that we could measure a runner’s brain, wriggly babies are much more difficult.

If you look at the figures below, you’ll see what can happen in the data when the baby couldn’t stay still and quiet. It gets “noise” from the body movement, and as the noise overwrites the “real” brain activity we want to see, sadly, we can’t use it as our final data.

 

Figure 2: EEG wave examples. The left shows the data which includes “noise” from body movement while the data is collected. The right shows the data which has little noise. Both are created using the author’s unpublished data only for illustrative purposes

Also, not many babies are happy to wear the cap. The cap needs to be wet (either with water or gel) to sensitively pick up changes in electrical activities happening inside the brain, so it can be pretty annoying even for adults to wear. It’s no surprise that babies wouldn’t want to keep wearing it for long, or they want to pull it off in the middle of their session.

So, it is not an easy job to collect good brain data from babies. But then, why should we be bothered about baby brains after all? In my next blog, we’ll look at why 🙂

 

If you’re interested in this topic-

TED talks;
– Playlist “The Genius of Babies”
– TED talk by Professor Rebecca Saxe  at MIT, talking about baby brain research (using fMRI not EEG)

Web articles;
– About Neuroplasticity
“What is brain plasticity and why is it so important?”
– General articles from baby brain scientists
“What Is Going on in Babies’ Brains When They Learn to Do Something?”

Reference
[1] Caton, Richard. (1875). The electric currents of the brain. British Medical Journal, 2. 278. Retrieved from http://echo.mpiwg-berlin.mpg.de/ECHOdocuView?url=/permanent/vlp/lit27690/index.meta
[2] Berger, H. (1929). Über das elektroenkephalogramm des menschen. Archiv für psychiatrie und nervenkrankheiten87(1), 527-570. Retrieved from https://pure.mpg.de/rest/items/item_2281721/component/file_2281720/content
[3] SAGA 32/64. (2018, November 29). Retrieved from https://www.tmsi.com/products/saga32-64/.
[4] Britton, J.W., Frey, L.C., Hopp, J.L., Korb, P., Koubeissi, M.Z., Lievens, W.E., Pestana-Knight, E.M. and St, E.L. (2016). Electroencephalography (EEG): An introductory text and atlas of normal and abnormal findings in adults, children, and infants. American Epilepsy Society, Chicago.
[5] Blocka, K. (2017, September 14). EEG Electroencephalogram: Mayfield Brain & Spine. Retrieved December 26, 2019, from https://mayfieldclinic.com/pe-eeg.htm.
[6] Cohen, M. X. (2014). Analyzing neural time series data: theory and practice. MIT press.
[7] Parise, E., Reid, V. M., Stets, M., & Striano, T. (2008). Direct eye contact influences the neural processing of objects in 5-month-old infants. Social Neuroscience3(2), 141-150. https://doi.org/10.1080/17470910701865458
[8] Banks, D. (2016, April 4). What is brain plasticity and why is it so important? Retrieved December 27, 2019, from https://theconversation.com/what-is-brain-plasticity-and-why-is-it-so-important-55967.
[9] Kolb, B., Harker, A., & Gibb, R. (2017). Principles of plasticity in the developing brain. Developmental Medicine & Child Neurology59(12), 1218-1223.
https://doi.org/10.1111/dmcn.13546
[a] Photo retrieved December 26, 2019, from https://www.flickr.com/photos/piedmonthealthcare/7631904636/
Photos without source specification are from Lancaster Babylab.