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This lesson is a part of an audio course Brain Science for Non-Scientists by Wilf Nelson

In this episode, we are going to be talking about EEG or electroencephalography and MEG or magnetoencephalography. They sound like very scary terms, and I'll be honest anything past the most basic explanation is a graduate-level topic, but it can be understood.

Before we start, you probably want to even know why you need to know this. The reason is EEG is the easiest method of brain imaging to do, it is hard, but EEG caps only cost a few thousand so most companies can get hold of one and start making all sorts of claims that their internal tests with their products have shown amazing things you wouldn't believe. Just click on the payment tab below. Brain scientists also very rarely buy from such companies; that is because we know what EEG can and can't do. I am going to teach the basics, so you and your family don't get caught out.

The brain's neurons fire electrical signals; no one disputes that so this is safe ground to start on, they fire electrical signals many times a second actually, but it is a really really tiny electrical signal. That firing goes through the neuron to then hit the end of the axon, the output wire of the cell, to fire chemicals called neurotransmitters. So EEG only sees the electrical signals, the brain is very conductive, and those signals don't just travel down the axons but also through the brain and out of the skull to the scalp. Again very very tiny signals, millivolts, and your nearby plug uses hundreds of actual volts. But that means already we only see one part of the neuron's firing, the electrical part and we have to accept without cutting open brains we are blind to the rest of what is going on with EEG.

Lesson number one, EEG is limited only to the electrical signals, and those electrical signals are used to make neurons do all sorts of chemical firing we just can't see with EEG alone. Anyone telling you EEG can make claims about the chemicals in the brain is just not telling the whole truth.

Now we get to the part where science gets involved. Ok, the brain is always active, even in sleep, even in my work where I study how neurons compete and try to make other neurons inactive they are still really active, just less active. So you get this really noisy data, and by noisy I don't mean super clean brain waves like in a movie, but instead, 250 or more electrodes all with very wiggly lines made up of dozens of signals in and of themselves that the computer can only represent as a single line per electrode. Well, that's a start but not great. My own description shows how complicated it is. So to give you the tools to understand when someone is lying or just wrong here is how an EEG study goes down.

First, we make the study, we have to really carefully design it, and if someone is explaining EEG and glosses over this, then something is very wrong. That is like saying you won a car race; cool was it a drag race, Le man 24 hours, you and your kid in go-karts, saying you won a race is meaningless without context just like saying an EEG experiment showed… and then craziness that makes a scientist roll their eyes.

So back to science, let's say I want to know how your brain creates your sense of vision. Well firstly that isn't going to happen, vision is enormously complex, and that is something thousands of scientists will try to understand over decades to centuries. Ok, let's say I want to know how your brain understands colour slowly changing and we are going to need two conditions. Why two? Well, here is why.

Lesson number two, EEG is so noisy we can only really measure changes, you in one condition of an experiment versus another. If someone says, we see a huge change in brain waves thanks to this app or drug, compared to what? Is it compared to doing nothing, just resting, or compared to another app? People hide what they are doing behind vague language, and for EEG without comparisons, it is super hard to tell what the brain is doing.

There is a newer branch of EEG research called resting-state data where you measure how the brain interacts and sends signals when it is resting because the brain is always active, but that is only in research circles right now. Resting-state data won't make you smarter; it won't make you more productive or memorise things better; it is neuroscientists studying how the brain works because they want to.

The take away from this episode is that when you see EEG in the news or adverts, it makes it seem that by just plugging on a cap and measuring a couple of electrodes you get a window into the brain. You get told people have data showing amazing memory improvements or better mood all from their product and an EEG cap. The reality is a lot tougher than that, EEG caps are filled with hundreds of electrodes pumping out millions of pieces of data that take scientists months to analyse. EEG can't pinpoint an exact thought, it needs proper controls, and it only sees one aspect of the brain. To go deep into the brain, we need other methods, we need MRI.

Next lesson we will talk about MRI and the beautiful images of the brain everyone has seen flashed up on the news, what do they actually mean?

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Written by

Wilf Nelson