A new study has found evidence that a section of our neurons, called the dendrites, aren’t the passive receivers we’ve always assumed them to be.
Instead, researchers have found that dendrites generate up to 10 times more electrical pulse spikes than parts of our brain cells called the soma, which until now were thought to be the main area to produce these electrical signals.
If verified, the study could change our understanding of neurons, and how the various parts of the human brain work together.
“Knowing [dendrites] are much more active than the soma fundamentally changes the nature of our understanding of how the brain computes information,” said one of the team, Mayank Mehta, from the University of California, Los Angeles (UCLA).
“It may pave the way for understanding and treating neurological disorders, and for developing brain-like computers.”
Dendrites are long, branch-like structures that make up over 90 percent of our neuronal tissue. They’re connected to the soma, which is the part of the neuron that surrounds the nucleus.
Here’s what they look like:
According to traditional thinking, somas generate the electrical pulses, also known as ‘spikes’, that brain cells use to communicate with each other.
Until recently, scientists generally assumed that these somatic spikes activated the dendrites, which then passively passed the currents onto other neurons’ somas – but this had never been directly tested.
Although recent studies of human brain slices had shown that dendrites could generate spikes, it wasn’t known if this happened naturally, and it hadn’t been shown in a live animal model.
“It was neither clear that this could happen during natural behaviour, nor how often. Measuring dendrites’ electrical activity during natural behaviour has long been a challenge because they’re so delicate.
In studies with laboratory rats, scientists have found that placing electrodes in the dendrites themselves while the animals were moving actually killed those cells.”
Obviously, this wasn’t an ideal situation, so the UCLA scientists placed the electrodes near the dendrites in rats, instead of on them.
They were able to measure the dendrites’ activity for four days,while the rats performed activities such as moving through a maze.
What’s interesting is that the researchers found many more spikes in dendrites than somas – five times more whilen the rats were sleeping, and up to 10 times more while they were exploring.
This is very different to the established understanding, and could show that our brains have much more ‘computational’ power than we thought.
“A fundamental belief in neuroscience has been that neurons are digital devices. They either generate a spike or not. These results show that the dendrites do not behave purely like a digital device,” said Mehta.
“Dendrites do generate digital, all-or-none spikes, but they also show large analogue fluctuations that are not all or none. This is a major departure from what neuroscientists have believed for about 60 years.”
So how much more processing power do we suddenly have in our brains?
Mehta explains that because dendrites are nearly 100 times larger in volume than somas, the large number of dendritic spikes means we could have over 100 times the processing capacity than we thought.
That’s a pretty big stretch, and more research will be needed before we can confirm exactly how much processing power our brain actually has.
It’s also important to note that this study has only been investigated in rats – we’d still need to investigate if the dendrites are behaving similarly in our own brains as they are in the animal models before we can start confirming any such numbers.
But these findings are an impressive step for the neurological field – and it may one day lead to better ways to treat neurological disorders, and even the basis behind how we learn.
“Our findings indicate that learning may take place when the input neuron is active at the same time that a dendrite is active – and it could be that different parts of dendrites will be active at different times, which would suggest a lot more flexibility in how learning can occur within a single neuron,” said one of the team, Jason Moore.
The research has been published in Science.