Have you ever wondered what goes on in your brain while you’re reading a sentence? Or how we can track that brain activity so we can do cool things such as move a robotic arm? Well you’ve come to the right place. Welcome to the world of EEGs (aka electroencephalograms); small devices used to track the electrical activity in your brain. Despite being around for some time, EEGs are still the most common type of technology used for BMIs at the moment as they are non-invasive (so no surgery necessary on the patient).
So let’s learn more about how they work…
Electroencephalography is a method used to record all of the electrical activity generated by the brain by placing electrodes on the surface of the scalp.
In your brain, there are hundreds of thousands of cells called neurons which are all interconnected via synapses, which is when electricity is transferred through the cells. These synapses essentially either help to move information across neurons (which is called excitatory activity) or prevent the movement of information from one neuron to another (inhibitory activity). First, the electrical signals are transmitted from the dendrites to the cell membrane where they meet the axon hillock. If both the excitatory synaptic potentials and the inhibitory synaptic potentials meet the threshold, the signal gets passed through, sending electricity down the myelin sheath to the axon terminals. Essentially, the axon hillock decides whether or not the electrical signals should go on to other cells. Now during this, the synaptic activity generates a small electrical impulse called post-synaptic potential. Since the electrical impulses are so small, it is very difficult for any sort of technology to detect it. However, whenever a group of around one thousand neurons or more fire together, they generate an electrical field that is strong enough to spread through tissue, bone and skull, eventually allowing for it to be measured from the scalp.
The majority of signals that are actually able to be captured by EEGs are from cortical pyramidal cells which add up to be around ten to fifty thousand neurons. Although this may seem to be a large amount, it is tiny in comparison to the number of neurons in the entire cortex. EEGs are generally less powerful than other methods due to the fact that they are a non-invasive method, yet they can still accomplish a lot of things as I will talk about later on.
Once the raw data from the EEGs is gathered, the most common way to analyse it is via a Fourier Transformation. This transformation extracts the frequencies in the data at a certain point in time and helps to lead to the final result of a frequency spectrum diagram.
What can we do with this information?
There are many applications for EEGs, even ones outside of BMIs. EEGs have been used in the past for things from neuromarketing to just general neuroscience research. Despite this, EEGs still are extremely popular for BMIs due to their low cost, good temporal resolution, ease of use, and portability.
Although there have been setbacks as to EEGs not being as powerful as other invasive methods, a research group at the University of Minnesota was able to make an EEG-based BMI accomplish tasks close to an invasive BMI. Essentially, by using advanced functional neuroimaging, Bin He was able to have a non-invasive EEG BMI control the flight of a virtual helicopter in 3-dimensional space, based on motor imagination. As if this wasn’t cool enough already,, in June 2013, the same lab had developed the technique to fly an actual remote-control helicopter through an obstacle course.
And all this was from just one lab out of hundreds if not thousands across the globe. As of right now, the main applications of EEGs are in neuroprosthetics, brain mapping, disorders of consciousness, and just the general controlling of machines. However, there’s so much more, from making more immersive video game experiences to synthetic telepathy. I mean, how crazy is that?
Overall, EEGs are one of the most promising types of technology for the implementation of BMIs in the near future due to their non-invasiveness. Furthermore, thanks to all of the life-changing applications it can bring, EEGs might even allow us to do crazy stuff such as communicate telepathically. And the best thing about it is that all these new technologies will most likely become available within our lives. With BMIs, who knows what the world would look like 20 years from now…
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