Scientists have identified a unique form of cellular messaging that occurs in the human brain. It reveals how much we still have to learn about its mysterious inner workings.
Interestingly, this discovery suggests that our brains may be more powerful computational units than we realized.
In 2020, researchers from institutes in Germany and Greece reported a mechanism in the brain’s outer cortical cells that produces a new “input” signal on its own, a signal that could provide individual neurons with another way to carry out their logical functions.
By measuring electrical activity in pieces of tissue removed during surgery in epilepsy patients and analyzing their structure using a fluorescence microscope, neuroscientists found that individual cells in the cerebral cortex use not only the usual sodium ions to fire, but also calcium.
This combination of positively charged ions triggered waves of electrical potential never seen before, called calcium-mediated dendritic action potentials, or dCaAPs.
Brains—especially human brains—are often compared to computers. This analogy has its limitations, but on some levels the machines perform tasks in similar ways.
Both use electrical voltage to perform various operations. In computers, this is in the form of a simple flow of electrons through junctions called transistors.
In neurons, the signal is in the form of a wave of open and closed channels that exchange charged particles such as sodium, chloride, and potassium. This pulse of flowing ions is called Work potential.
Instead of transistors, neurons conduct these messages chemically at the end of branches called dendrites.
“Neurons are fundamental to understanding the brain because they are the core of what determines the computational power of individual neurons,” says the Humboldt University neuroscientist. Matthew Larcombe told Walter Beckwith At the American Association for the Advancement of Science in January 2020.
Dendrites are the traffic lights in our nervous system. If the action potential is large enough, it can be transmitted to other neurons, which can either block or pass on the message.
This is the basic premise of our brain – electrical voltage ripples that can be collectively communicated in two forms: either And Message (if x And If triggered, the message is passed); or or Message (if x or y is turned on, and the message is passed).
This is certainly more complex than anywhere else in the thick, wrinkled outer portion of the human central nervous system, the cerebral cortex. The innermost layers, the second and third, are particularly thick, and filled with branches that perform the higher-level functions we associate with sensation, thought, and control of movement.
The researchers closely examined the tissues of these layers, connecting the cells to a device called a somatic dendritic patch synapse to send active potentials up and down each neuron, and record their signals.
“There was an amazing eureka moment when we first saw the tree’s action potential,” Larcom said.
To make sure any findings were not unique to people with epilepsy, they re-checked their results in a small number of samples taken from brain tumors.
While the team conducted similar experiments, On miceThe types of signals they observed buzzing through human cells were very different.
More importantly, when they gave the cells a dose of a sodium channel blocker called tetrodotoxin, they found a signal. And it wasn’t until they blocked the calcium that everything went quiet.
The discovery of calcium-mediated action potentials is interesting enough. But modeling how this sensitive new type of signal works in the cerebral cortex revealed a surprise.
In addition to logic And And or– Type functions, these individual neurons can act as ‘Exclusive’ or (XOR) intersectionswhich only allows a signal to be indicated when another signal is classified in a certain style.
Traditionally, XOR “It was believed that the process required a network solution.” The researchers wrote:.
More work needs to be done to figure out how dCaAP proteins act across whole neurons, and in a living system. Not to mention whether these proteins are man-made, or whether similar mechanisms have evolved elsewhere in the animal kingdom.
Technology is also looking to our nervous system for inspiration on how to develop better devices; knowing that our individual cells have more tricks up their sleeves could lead to new ways to connect transistors.
How this new logical tool built into a single neuron translates into higher functions is a question that future researchers must answer.
This research was published in Sciences.
The original version of this article was published in January 2020.
“Beer aficionado. Gamer. Alcohol fanatic. Evil food trailblazer. Avid bacon maven.”