Brains may conjure up images of zombie hordes feasting on people like an all-you-can-eat-buffet, but the living hardly know more about the human brain than the undead.
There is still a vast expanse of the human brain and nervous system that eludes scientists. Understanding our brains means looking further into brain cells, or neurons, and what they are capable of. While many recent studies and technology such as AI and Neuralink have done work advanced enough to sound like the stuff of a sci-fi novel, we still hardly know anything about the thing in our skulls whose sophisticated function gave us the name homo sapiens.
Forget the idea that humans supposedly know better than just about everything else on this planet. If we really want to find out how the brain works across species, we need to analyze neurons and, not to tempt any zombies out there, all the flavors they come in. A group of scientists from the Allen Institute, led by Hongkui Zeng. She led a study published in Nature Neuroscience and is leading an effort to create the first periodic table of the brain.
"We use single-cell gene expression data to categorize cells from different parts of the brain into types," Zeng told SYFY WIRE. "We validate these cell types by linking their gene expression with the characteristic shapes and physiological properties of the cells."
The Allen Institute team has almost completed a catalog of cell types from the mouse brain, and will soon undertake the enormous task of puttingone together for the human brain.
What constitutes intelligence is highly questionable. This is the thinking of Gül Dölen of the Brain Science Institute at Johns Hopkins, who is also developing a similar periodic table. Such a format would also allow us to more easily compare and contrast. Humans might be able to write epic novels or do mind-blowing astrophysics, but when it comes to our sense of smell, we are downright stupid compared to a pit viper. Bats can easily out-hear us, spiders have an amplified sense of touch, and we would fail a night vision challenge if we had to compete against a tarsier or even—wait for it—a cockroach.
Dölen was the daring scientist behind a study that involved giving MDMA (aka ecstasy) to octopi to see what happened in their brains. She found that, despite our obvious lack of tentacles, there were parallels between the octopus and human brain on ecstasy. The average octopus is rather antisocial, but suddenly wants to warp all eight arms around other octopi when the MDMA has taken effect. Octopi and humans have shared genes. Creating a periodic table of every possible type of brain and brain cell could make information about evolutionary relationships like this more accessible.
"The greatest mysteries of the brain we hope to see elucidated are how brain works to generate thoughts, emotions and behaviors, and then how these processes go awry in different kinds of brain diseases," said Zeng. "Understanding how brain works and using that knowledge to treat brain diseases is the ultimate goal of our research."
Neurons could reveal different types of intelligence (or any other aspect of the brain) along with their connection to other types of the same aspect in a periodic table. Unlike Dölen, Zeng is focused on applying the knowledge gained through a periodic table of neurons to brain diseases and disorders. Though mice only have 80 million neurons — nothing compared to our 86 billion — it was somewhere to start for Zeng and her team. The researchers analyzed the electrical activity of 2,000 of those neurons from the part of a mouse’s brain that controls visual processing. Having a catalog of brain cells will help scientists see the funcitons of different cell types, how some work together, and what can possibly go wrong.
Unsurprisingly, categories from this study were found to be similar to categories Zeng had figured out in a previous study that categorized gene expression. The future periodic table doesn't even have to stop at the brains of extant species. It is possible that the DNA of extinct species could give us insights into how certain neurons and their abilities evolved, especially in humans. Neanderthals may not zombify, but their genes may be able to help us from beyond the grave. Zeng believes there could be missing links we haven't yet discovered.
"Understanding the evolutionary origins of brain cell types will help us understand what makes the human brain unique," she said. "To find out how brain cell types have evolved, we need to identify and compare the cell types from different animal species. Sometimes there may be critical gaps in such comparison, and the brains of extinct animals and hominids could potentially help to fill these gaps."
What a periodic table of the brain could tell us about the function of neurons in every known organism that has them are almost limitless. Cells can be categorized by various features, from morphology to activity, and connections between these features can tell scientists which cell type groups are closest to each other. They can also show how individual neurons relate to neural circuits in the brain, which could be an asset to upcoming technology like Neuralink. The cells are almost building the periodic table themselves.
"These new studies can reveal mechanisms underlying many brain functions and properties including intelligence, but it will take a lot of studies to get there," Zeng said. "So I would say obtaining a brain periodic table is just an essential first step for solving the mysteries of the brain."
With research like this, just be sure to take extra precautions in guarding the lab against zombies.