Last time we talked about how to use fMRI for mind reading and what eye-tracking has to do with virtual reality; but what about methods enabling brainwave-controlled machines, you might ask? What about techniques allowing us to understand mental diseases on molecular level? (or you might not ask but I’m gonna talk about it anyway).
Electroencephalography (EEG) and Brain-Computer-Interface
Electroencephalography may sound like a scary torture technique but in fact the most harm it can cause you is dozing off due to a boring experiment. Non-invasive and harmless, EEG is the method that first makes people look silly by putting Professor X-style caps on their heads and then measures electrical activity going on in there.
As you might know or remember, our neurons communicate by passing on electrical signals to each other. Now, when one neuron fires its activity is immensely small; yet if voltage change occurs for thousands of neurons in synchrony, they generate an electrical field strong enough to surpass the skull and to be detected on the surface of the head (read up here if you’re interested in more in-detail biophysics behind it). Recording of these signals is where the silly-looking caps come into play: they contain electrodes actually measuring the electrical activity. The said activity is first being amplified by around 10.000 times (passing meninges, skull and scalp is no easy job! It makes the signal very weak) and then transmitted to an EEG monitor where you can observe your brainwaves (or sequence of voltage values, if you like).
EEG is excellent in allowing us to monitor the brain activity in real time capturing second-to-second changes (in comparison, fMRI signal is always a bit delayed). It’s spatial precision lags a bit behind though -- we need sophisticated algorithms to estimate where exactly the signal is coming from. There are several distinct brain waves pattern, each with its own unique personality -- think about them as your brain changing gears depending on what it needs to do in the moment. There are delta waves (typically seen during deep sleep), theta waves (dreaming), alpha (relaxation and drowsiness), beta (alertness) and gamma (one of the unsolved neuroscience mysteries; might be looking at cat pictures).
Now, seeing your brainwaves irl is undeniably impressive, but what about the brain-controlled machines I lured you with? Indeed, we can make some pretty damn awesome sci-fi scenarios come true with EEG: we can use it to make you control stuff with your mind! (or to create brain-computer-interfaces, if you’re a less sensational type). The scope of potential applications ranges from controlling a virtual helicopter in a 3D space to actually useful stuff like controlling robotic limbs -- all with your mere thoughts. While the possible perks for gamers are indisputable (imagine not needing a joystick while gaming and using the freed hand for more pizza instead!), disabled people are the ones this technology will benefit most.
So how do these weak electrical signals from under your skull turn into movements of your robotic arm? It bases on the idea that specific mental activity has specific neural underpinnings, a specific pattern of EEG signal. The device would record different patterns of scribbly waves for imagining lifting the arm and, say, thinking “yes” when looking at a letter. In order to control their brain activity and to make these signal patterns clearly distinguishable from each other (and thus easy to interpret for the algorithms) patients (or gamers) in question should train their imaginative skills very hard. What really helps is feedback: for instance, every time you try to imagine a specific motion a computer screen shows you the arrow pointing in the direction it thinks you wanna move. After the user has learnt how to use the power of imagination, software connected to the robotic arm (leg, penis, computer cursor) is fed all the different possible patterns so that it can recognize what you want and send along the command activating whatever is it they’re controlling.
(BCIs do not only use EEG; check out this to see what a BCI using implanted electrodes can do for locked-in patients!)
Cellular neuroscience and understanding mental illness
EEG, fMRI and eye-tracking are all fine and dandy, but what does actually run the show? Spoiler: things so small even Donald Trump’s hands could grasp them. The microscopic processes taking place in and in-between neurons are immensely important for us to understand and this is exactly what cellular neuroscience does. There is a lot you can do with cells: right now, for instance, I’m working in a lab where we count how many new cells were “born” in hippocampus -- our memory center -- under different conditions (high sugar diet/exercise/etc). One can explore cell behaviour in vivo -- on a living organism, in vitro -- in a glass and outside of the said poor living organism and in situ -- something in between, like investigating the brain without removing it from the mice who is already dead (or “sacrificed” as we dark scientists like to say).
An example of in vivo experiment would be taking a genetically modified mouse whose neurons of interest are fluorescent, cutting a hole in its skull and using a cool technique called two-photon microscopy to look at these fluorescent cells located relatively deep in the brain. Sounds a bit complicated and believe me, it is a bit complicated. Basically, while your mouse is awake but head-restrained the microscope shines high-energy light (which is on the blue end of the visible light spectrum) on its brain. The fluorescent cells absorb this light, get excited, and, after a short while as their excitation declines, emit lower-energy light (green, red, yellow etc). The microscope catches this colourful light through a specifically adjusted filter and voila -- you have a pretty picture!
Fluorescent microscopy can also be performed in case your experiment calls for a sacrifice of the mouse. The brain is then removed, cut in super thin slices and bombarded with all kinds of chemical solutions in order to make the cells fluorescent. Normally, the first step of this bombardment (or as we scientists call it, “staining”) includes putting the slices in a solution with antibodies that connect to cells or proteins we are interested in; in the second step we put fluorescent antibodies which connect to the primarily antibodies. This way cells of interest become all bright and shiny so that we can put it under a fluorescence microscope and enjoy another batch of pretty pictures!
Cellular neuroscience has immensely contributed to our understanding of why mental illnesses are the way they are and what needs to be done to make them go away. Thanks to it we were able to find out that when you’re depressed your hippocampus (gateway to memory) does not produce as many new cells anymore and that antidepressants seems to reverse this process by promoting production of proteins which help neurons grow; that in some cases it is enough to artificially increase the neurogenesis (=birth of new cells) rate to reduce anxiety and depression; that chronic stress tends to destroy a special kind of protein which plays an important role for proper communication between neurons and that antidepressants restore its production and make mice feel better. We learnt that there is a dopaminergic imbalance in schizophrenia and that neural stem cells do not properly develop into neurons for these patients; we also are able to find new strategies preventing Alzheimer’s. Now this was a lot of facts in short time, so have another pretty picture!