Scientists have identified a unique cell message that occurs in the human brain. It shows how much we have to learn about its mysterious inner workings.
Excitingly, the discovery hints that our brains may be more powerful computational units than we realize.
In the year In 2020, researchers in Germany and Greece reported a mechanism in the brain’s outer cortical cells that produces a novel ‘graded’ signal, providing another way for individual neurons to perform their logical tasks.
By measuring the electrical activity in surgically removed tissues from epileptic patients and analyzing their structure with fluorescence microscopy, neurologists found that individual cells in the cortex not only used the usual ‘fire’ of sodium ions, but also calcium.
This combination of positively charged ions initiates unprecedented voltage waves, known as calcium-mediated dendritic action potentials, or dCaAPs.
Brains – especially the human kind – are often compared to computers. Similarity has its limitations, but on some levels they perform tasks in the same way.
Both use electrical voltage to perform different tasks. In computers, it takes the form of a simple flow of electrons through junctions called transistors.
In neurons, the signal is in the form of waves that exchange charges such as sodium, chloride, and potassium, opening and closing channels. This flow of ions is called pulse A Functional capacity.
Instead of transistors, neurons conduct these messages chemically at the end of branches called dendrites.
“Dendrites are central to understanding the brain because they are the main component that determines the computing power of individual neurons,” says the Humboldt University neuroscientist. Matthew Larcum told Walter Beckwith. In January 2020 at the American Association for the Advancement of Science.
Dendrites are the traffic lights of our nervous system. If the action potential is important enough, it can be transmitted to other neurons, which can block or transmit the message.
This is the logical basis of our brain – voltage waves can be transmitted together in two ways: either And message (from x And y is triggered, the message is transmitted); or one Or message (from x Or y is triggered, the message is transmitted).
Certainly, nowhere is it more complex than in the dense, wrinkled outer part of the human central nervous system; Cerebral cortex. The deep second and third layers are especially thick, we associate them with emotion, thought and motor control and are packed with branches that perform higher order functions.
The researchers looked closely at these cells by connecting them to a device called a somatodendritic patch clamp to send individual neurons up and down and record their signals.
“It was a ‘eureka’ moment when we first saw dendritic action potentials.” said Larkum..
To make sure any findings weren’t specific to people with epilepsy, they double-checked their results with a few samples taken from brain tumors.
When the group did the same experiments on miceThe signals observed in human cells are very different.
More importantly, they still got a signal when they treated the cells with a sodium channel blocker called tetrodotoxin. By simply withholding calcium they all quieted down.
The finding of a calcium-mediated action-potential is interesting enough. But modeling the way this sensitive new type of signal works in the cortex has revealed something surprising.
In addition to logic And And Ortype functions, these single neurons can act as ‘special’ Or (XOR) interfacesThis symbol allows only when another symbol is rated in a different fashion.
“Usually the XOR The operation is assumed to require a network solution.” The researchers wrote.
More work needs to be done to see how dCaAPs behave in whole neurons and in living systems. Not to mention whether this is a human-thing or if similar mechanisms have evolved elsewhere in the animal kingdom.
Technology is also looking to our own nervous system for inspiration on how to develop better hardware; Knowing that our own cell has a few more tricks up its sleeve could lead to new ways to network transistors.
How this new logic tool packed into a single neuron translates into higher functions is a question for future researchers to answer.
This study was published in Science.
A version of this article was originally published in January 2020.