This is an email from Inside Your Head 🧠, a newsletter by Elemental.
Your Brain Is Electric
This is a modified excerpt from Inside Your Head 🧠, a weekly newsletter exploring why your brain makes you think, feel, and act the way you do, written by me, Elemental’s senior writer and a former brain scientist. Subscribe here so you won’t miss the next one.
Like nearly all complex machines, your brain runs on electricity. Every time a neuron fires in order to communicate with another neuron, a little burst of electricity courses through the cell to power the message. Scientists use these electric pulses to measure and track activity in the brain, and this research has contributed to a lot of what we know about what different brain regions do.
One way researchers measure electrical activity is a method known as EEG (electroencephalography), where a person wears a cap made of a web of electrodes that sits on top of their head. However, because the electrodes are reading neural activity through the scalp, EEG recordings aren’t very precise. It can tell you roughly when and what type of activity is happening but not where.
A more spatially accurate — but much more invasive — technique is to implant electrodes directly into a person’s brain. This type of research only happens on the rare occasions that someone is already undergoing brain surgery because even the most obsessed neuroscientist wouldn’t suggest opening up your skull just to take a look inside. Many people who’ve had deep brain recordings taken suffer from severe epilepsy, which is a disorder defined by abnormal electrical activity in the brain — what we know of as a seizure.
In the most severe cases of epilepsy, scientists need to identify the precise location where the seizures start in order to treat them. To do so, they place electrodes either directly onto the cortex (the outer layer of the brain) or implant them deeper into the tissue; then they record for several days until they can find the foci of the seizures. During that time, while the electrodes are already in the brain, some psychologists and neuroscientists also conduct a little research — with the patient’s explicit permission, of course.
One study from 2018 used this method to track the electrical activity of 16 epilepsy patients’ thoughts as they performed simple tasks. Tracking neural activity across different brain regions, the researchers found that seeing or hearing a word activates the visual or auditory processing parts of the brain (not surprising). Next, the neural activity moved into the prefrontal cortex, which is involved in higher order cognitive processes like planning for the future or working memory. The scientists speculate that people are processing information in the prefrontal cortex, deciding what to do next. Lastly, the motor cortex gets activated when an action is decided upon and a response is to be made, whether it’s pushing a button or speaking a word. Interestingly, there is an overlap in activity between the prefrontal and motor regions, as if the brain is primed to respond with an action even before it’s decided what the action will be.
In addition to recording electrical signals in the brain, scientists can also change the activity by zapping neurons with a small current. Deep brain stimulation, as it’s called, is used to treat neurological disorders, most notably Parkinson’s disease, by shocking malfunctioning areas of the brain. In Parkinson’s, the electrode is implanted into an area called the subthalamic nucleus, which helps control motor movements. Delivering a steady current to this area can help relieve both the tremors and difficulty moving that are characteristic of Parkinson’s.
A more advanced type of electrical brain stimulation involves only shocking the brain at the precise moment when something is going wrong. With this technique, two electrodes are implanted in the brain — one to record activity and the other to deliver a mild jolt. A tiny computer placed into the skull monitors the electrical recording and identifies when the activity starts to become abnormal, like when a seizure is about to start. At that point the second electrode goes off like a pacemaker, resetting the activity back to normal.
I think this technology is some of the coolest, craziest neuroscience research happening today, and I’ve written about it a couple of times for Elemental and OneZero. Because not only are scientists treating epilepsy with this technology, they’re also attempting to treat mood and behavioral disorders, like depression and binge-eating disorder.
A fascinating study published last month was the first to show how this type of neural stimulation might work for depression. The scientists took an individualized approach, inserting 10 electrodes into the brain of a woman who had severe treatment-resistant depression. They monitored her for days, mapping how her mood shifted when they stimulated each region. One of the best responses came when they targeted an area called the ventral striatum, which is part of the brain’s reward circuitry; the woman giggled for the first time in years.