Humans Share a 'Universal' Brainwave Pattern with Other Primates
And scientists think they know what these patterns mean
Hiya!
We, Humans, have tried to separate ourselves from the rest of the Natural world for the last several thousand years. Yet modern research using advanced technology is painting a very different picture. Rather than affirming our egotistical notion that we are superior to other animals, research is finding a growing number of similarities we share with them.
You’ll find several examples in the Curious Adventure archive, and today, I’m sharing another one. A collaborative team of scientists identified distinct patterns of electrical activity throughout the six microscopic layers of the brain’s cortex. Remarkably, these patterns occur across the brains of multiple primate species, including us.
Previous Research
When André Bastos was a postdoctoral student at the Massachusetts Institute of Technology (MIT), he conducted several studies involving monkeys with Earl Miller, Bastos’ professor and a member of MIT’s Picower Institute for Learning and Memory. Throughout their research, they identified distinct activity patterns in six layers of the cerebral cortex — the wrinkly outer and, therefore, most visible part of the brain.
The brain’s cortex is responsible for many functions, including high-level emotional processing, working memory, and sensory information, and is generally considered “the seat of thought.” The neurons in the cortex are arranged in six microscopic layers ranging from superficial near the skull to deeper ones closer to the core, each with its own unique combination of cells and connections with other brain regions.
In the primates, Bastos observed fast-paced, higher-frequency waves of electrical activity in the cortex's higher, most superficial layers, while slower, lower-frequency waves hung out in the deeper layers.
The faster, higher-frequency waves are called gamma rhythms, which run between 50 and 150 hertz. Miller's research in 2016 indicates that gamma waves are linked to encoding and retrieving sensory information.
Meanwhile, the lower-frequency waves are alpha and beta rhythms that range between 10 to 30 hertz. Later research by Miller in 2021 suggests that lower-frequency waves help regulate the processing of the information carried by gamma rhythms.
Bastos, now an assistant professor of psychology at Vanderbilt University, suggests thinking of it as though the slower brain waves in the deeper regions of the cortex are the gatekeepers that decide what information enters and stays in conscious thought. He explains to Live Science:
"You have information coming in that can be represented by gamma bursts and spikes. And then you can have another mechanism for saying, 'I don't care anymore, turn that off.' That's the job of alpha-beta waves — to yank one thought off stage to let another on.”
Since then, Miller and Bastos teamed up with other scientists at Vanderbilt, MIT, the University of Western Ontario in Canada, and the Netherlands Institute for Neuroscience to investigate this intriguing brain activity further.
New Research
In January 2023, Miller, Bastos, and the international team of scientists published their new research in the journal Nature Neuroscience. In it, they show that the previously observed brain activity is more expansive than they realized and, further, is ubiquitous.
The team discovered the patterns in brain activity showed up not just in a handful of areas in the cortex, as Bastos initially found, but in fourteen. He told Live Science:
"What we have shown here is that it's not just present in one area or another area, but it's really present throughout."
They also discovered the pattern arises in the brains of at least three different primates: marmosets (Callithrix jacchus), macaques (Macaca), and us (Homo sapiens).
The Study
To conduct their research, the team surgically embedded tech called multi-contact laminar probes into the subjects’ cortex, which recorded activity in every layer of the cortex simultaneously. For the human subjects, the devices were implanted while the patients underwent brain surgery to treat movement disorders such as epilepsy.
Bastos explained that the multi-contact laminar probes are like a “very micro version” of the electroencephalogram (EEG), which is one method of recording electrical brain activity. Except EEG monitors brain activity through hair, tissue, and the skull via temporary electrodes that stick atop the head. With more barriers to penetrate, EEG readings are less precise and have lower-resolution pictures than the high-definition abilities of the multi-contact laminar probes embedded at the source.
After the scientists gathered the data, they fed it to an algorithm designed to decipher which cortical layers the activity came from. Doing so showed a universal pattern of cortical activity, consisting of a peak of gamma activity close to the skull in layers two and three of the cortex and peak alpha-beta activity in layers five and six, which are deeper regions near the subcortical areas. They also found a bit of crossover occurring in layer four.
After identifying the pattern in each primate species, the team also checked to see if it appeared in mice's brains — but the activity in mice's cortex didn’t match.
As for the function the pattern in the primate cortex serves, Bastos agrees with Miller’s theory that the slower waves play the role of gatekeeping information. While further research is needed to know for sure, Bastos and his colleagues think that the patterns likely reflect the same mental process in each primate species.
In the Future
Another aspect of the scientists’ theory is that imbalances between high-and-low-frequency brain waves may be the foundation of various mental health conditions.
For instance, things like Attention Deficit Hyperactive Disorder (ADHD) may arise when higher frequency waves dominate the lower frequency waves, meaning too much sensory information gets in. Meanwhile, when the lower frequency waves dominate, not enough sensory information gets in, which may result in conditions like schizophrenia.
Miller, who is one of the senior authors of the new study and the Picower Professor of Neuroscience at MIT explains in a statement:
“The proper balance between the top-down control signals and the bottom-up sensory signals is important for everything the cortex does. When the balance goes awry, you get a wide variety of neuropsychiatric disorders.”
Next, the researchers want to investigate whether measuring these oscillations could help better diagnose such disorders and further refine their discovery. In the January Nature paper, the primate and human brain recordings occurred while the subjects were resting, not engaged in any tasks. So, in the future, the study may be repeated while the subjects perform an activity.
Mainly, though, Bastos is looking forward to future technological advancements that will hopefully allow researchers to record tens or thousands of neuronal activities simultaneously throughout different brain regions. He says:
"The hope there is that we can begin to understand in a much deeper way what is the neural basis of thought, for example, or what is the neural basis for more complex types of cognition, which we haven't really been able to touch yet."
Perspective Shift
Bastos and the other scientists have good reasons to suggest that electrical activity reflects how the brain consciously shifts focus from one piece of information to another. I didn’t have space to dive too deep into their reasoning, but MIT’s news release explains it well. But even if that isn’t the pattern’s function, the universality of these oscillations likely means they play an essential role in the brain.
I’m super curious about how many more brain patterns we share with other animals. Maybe this is just the first of many neural similarities shared among species. We likely won’t ever know how different species experience life — known as umwelt — but perhaps deciphering brain wave activity will help bring the picture a little closer into focus. At the very least, hopefully, such research will humble us some and remind us that we are not above, but part of the animal kingdom.
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I’ve read a lot about the brain, but this is new to me. I wonder how deeply Neuralink and other brain interface researchers are placing their equipment.