Scientists have discovered a unique form of communication between cells in the human brain that reveals how much we still have to learn about the brain’s mysterious inner workings. A fascinating discovery suggests that our brain may be a much more powerful computing device than we imagined.

In 2020, researchers from institutes in Germany and Greece reported a mechanism in the outer cells of the cerebral cortex that independently generates a new “cascade” signal and can give individual neurons a different way to carry out their logical functions.

Measuring electrical activity in areas of tissue removed during surgery from epilepsy patients and analyzing their structure using fluorescence microscopy, neurologists discovered that individual cells of the cerebral cortex use to “fire” not only the usual sodium ions, but also calcium. This combination of positively charged ions produced unprecedented voltage waves called calcium-mediated dendritic action potentials or dCaAPs (calcium-mediated dendritic action potentials).

Brain – especially human – is often compared to a computer. The analogy has its limits, but on some levels they perform tasks similarly. Both use the power of electrical voltage to perform various operations. In computers, this occurs as a fairly simple flow of electrons through junctions called transistors.

In neurons, the signal takes the waveform of the opening and closing of channels that exchange charged particles such as sodium, chloride, and potassium. This pulse of ion flow is called an action potential. Instead of transistors, neurons transmit these messages chemically at the ends of processes called dendrites.

“Dendrites are central to understanding how the brain works because they form the basis of what determines the computational power of individual neurons,” Humboldt University neuroscientist Matthew Larkum told Walter Beckwith at the American Association for the Advancement of Science in January 2020.

dendrites They are the traffic lights of our nervous system. If the action potential is large enough, it can be transmitted to other nerves that can block or transmit messages. This is the logical basis of our brain – voltage fluctuations that can be transmitted in two forms: either an “AND” message (if x and y are triggered, the message is transmitted further); or an “OR” message (if x or y fires the message is delivered).

Perhaps nowhere is this more complex than in the dense, wrinkled outer part of the human central nervous system (the cerebral cortex). The deeper second and third layers are particularly thick; It is full of branches that perform higher-level functions related to our emotions, thinking, and motor control.

The researchers closely examined the tissue of these layers by attaching the cells to a device called a somatodendritic patch clamp, which sent action potentials up and down each neuron, recording their signals.

“When we first saw dendritic action potentials, it was a ‘eureka’ moment,” says Larkum.

They double-checked the results on various samples from brain tumors to make sure any findings were not specific to patients with epilepsy. Although the team conducted similar experiments in rats, the types of signals they observed in human cells were quite different.

Importantly, when they dosed the cells with a sodium channel-blocking substance called tetrodotoxin, they still found the signal. But after blocking calcium, everything calmed down. It is quite interesting to detect a calcium-mediated action potential. But modeling how this sensitive new type of signal works in the cerebral cortex revealed a surprise.

In addition to AND and OR logic functions, these individual neurons can act as “exclusive OR” (XOR) connections that activate a signal only when another signal is evaluated in a certain way.

“Traditionally, XOR operation was thought to require a network solution,” the researchers write.

Additional studies are needed to see how dCaAPs behave in whole neurons and in a living system. Not to mention whether this is a human trait or whether similar mechanisms have evolved elsewhere in the animal world.

Technologies also look at our nervous system for inspiration to design better hardware; The knowledge that our own cells have a few more tricks up their sleeves could lead to new ways of networking transistors. Exactly how this new logical tool, crammed into a single neuron, will translate into higher functions is a question for future researchers to answer. This study was published on: Science.