Dendrites And The Beginning Of A Revolution

For many years, neuroscience has used various tools to try to “listen” to the conversations between neurons. In the same way that linguists decipher an unknown language, scientists try to decode neural firing patterns and uncover the grammar of the brain. In this universe to be explored, it seems that new stars have been born: the dendrites.

The latest research shows that neuroscience has so far only scratched the surface when it comes to estimating the capabilities of our brains. The University of California has discovered a hidden level of neuronal communication that occurs through dendrites. This could translate into up to a hundred times more brain processing capacity than is currently thought.

This is a discovery that could significantly change the foundations of conventional neuroscience. Until a few months ago these bases were supported by the belief that dendrites were a kind of passive wiring, whose job was to carry electrical signals to the neural body, the soma. This research, on the other hand, has shown that they are much more than just passive conductors. They generate electrical impulses, with peaks five times larger and more frequent than those coming from the nuclei of neurons. 

What does this discovery mean?

It could involve a radical change in neuroscientific knowledge about the functioning of the brain. It is also hypothesized that learning processes take place at the level of the dendrites and not in the soma of neurons. 

Neuroscience, to date, has argued that the electrical impulses emitted by cell bodies are the basis of our cognitive abilities. We now know that the dendrite does not play a passive role and that it also emits its own electrical signals.

This fact in itself is already surprising, however researchers argue that the dendrites are also intelligent. They are able, over time, to regulate their electric firing. A type of plasticity that has so far only been observed in neuronal bodies. This would suggest that the dendrites are capable of learning on their own.

Since these are much more active than the cell body, we can begin to understand that much of the information generated in a neuron is created at the level of the dendrites without passing through the cell body. That is, the latter can function as a computing unit and process their own information. An autonomy that was not suspected until a few months ago.

The capacity of our brain: research

The team of researchers led by Dr. Mayank Metha has devised a system that allows electrodes to be placed in mice near the dendrites. This device made it possible to pick up the electrical signals emitted by the animals in the waking phase, while they were moving, as well as during sleep. In this way they were able to record the electrical activity of the dendrites for four days and send the data directly to the computer.

The electrodes were connected to the brain area linked to movement planning, the posterior parietal cortex. It was thus observed that in the sleep phase the electrical impulses appeared to be irregular waves, each characterized by a peak. 

This means that  during sleep the dendrites “chat” with each other, and do so with electric shots up to five times faster than those originating in cell bodies. During the wake phase the firing speed is multiplied by ten.

Dendrites: here and now gauges

Another surprising discovery, which took place in the course of this research, concerns the type of signal emitted by the dendrites. The electrical signals may have been digital, but they also exhibited large fluctuations, nearly twice as many as the plugs themselves. This type of wide-range fluctuation suggests that the dendrites also exhibit analog-like processing activity. Something that has never before been seen in any pattern of neuronal activity.

How much processed by this impulse emitted by the dendrite seems to be related to time and space. Two types of signals were isolated from observing mice wandering around the maze. One in the form of cell body spikes, as an anticipation of a certain behavior (emitted, for example, before turning the corner). The dendrites, on the other hand, emitted their impulses as the animal turned the corner.

Neuroscience appears to have underestimated the processing capacity of the brain. Only from the point of view of the volume, and considering that the dendrites are a hundred times larger than the soma, it could be assumed that the brain actually has a processing capacity a hundred times greater than previously thought. Apparently, now that we know more about dendrites, neurons will no longer be the functional units of the brain.