Scientists have recently identified a unique form of cellular messenger that occurs in the human brain and has not been seen before.
Interestingly, this discovery hints that our brain may be a more powerful computing unit than we think.
In 2020, researchers from institutes in Germany and Greece reported on a mechanism in the outer cells of the cerebral cortex that itself generates a new “stepping” signal that can provide individual neurons with a different way to perform their logical functions.
By measuring the electrical activity in tissue sections removed during surgery from patients with epilepsy and analyzing their structure using fluorescence microscopy, neurologists have discovered that individual cells of the cerebral cortex use not only their usual sodium ions, but also calcium to “ignite”.
This mixture of positively charged ions fires previously unseen potential waves called calcium-mediated dendritic action potentials, or dCaAP.
The brain, especially the human brain, is often compared to a computer. This analogy has its limitations, but at some levels, tasks are performed in a similar way. Both of them use voltage to perform various operations. In computers, this happens as a fairly simple flow of electrons through junctions called transistors.
In neurons, the signal takes the form of a wave of opening and closing channels that exchange charged particles such as sodium, chloride, and potassium. This momentum of current ions is called the action potential.
Instead of transistors, neurons chemically relay these messages at the ends of branches called dendrites.
“Dendrites are fundamental to understanding the brain because they are the foundation of what determines the processing power of individual neurons,” Humboldt University neuroscientist Matthew Lark told Walter Beckwith at the American Association for the Advancement of Science in January 2020. Dendrites are traffic lights for our nervous system. If the action potential is large enough, it can travel to other nerves that can block or relay the message.
And this is the rationale behind our brains – voltage ripples that can be transmitted collectively in two forms: either a message AND (if x and y are triggered, the message is passed on); or an OR message (if x and y fire, the message is transmitted).
Nowhere is it more complex than the dense, wrinkled outer portion of the human central nervous system. cortex. The second and third deep layers are particularly thick, filled with ramifications that perform higher-order functions that we associate with feeling, thinking, and motor control.
The researchers closely examined the fabric of these layers, attaching the cells to a device called a neurosomatic patch terminal to send energy potentials up and down each neuron and record their signals.
“It was a ‘eureka’ moment when we first saw the action potential of dendrites,” Larkom said.
To make sure any findings weren’t unique to people with epilepsy, they reviewed their findings on a small number of samples taken from brain tumors.
While the team did similar experiments in mice, the types of signals they observed in human cells were very different.
Importantly, when they injected a sodium channel blocker called tetrodotoxin into the cells, the signal persisted.
In addition to the logical AND and OR functions, these individual neurons can function as “exclusive” OR (XOR) interrupts, which only allow a signal when another signal is classified in a certain way.
“Traditionally, it was thought that the XOR operation required a network solution,” the researchers write.
More work needs to be done to figure out how dCaAPs behave in all neurons and in a living system. Not to mention whether it was something human or similar mechanisms evolved somewhere else in the animal kingdom.
Technology also looks to our nervous system for inspiration to develop better devices.
This study was published in the journal Science.
Source: Science Alert
