Scientists have discovered that the brain is 10 times more active than previously thought.
In a study on components of the neurons known as dendrites, researchers found that they are not passive conduits as typically believed, but instead are electrically active in moving animals.
Not only could this mean that the brain has over 100 times the computational capacity than it’s been believed, but the discovery could also pave the way for the development of ‘brain-like computers.’
The finding runs counter to the long-held belief that somatic spikes were the main way we learn and form memories and perceptions.
“Dendrites make up more than 90 percent of neural tissue,” said UCLA neurophysicist Mayank Mehta, the study’s senior author. “Knowing they are much more active than the soma fundamentally changes the nature of our understanding of how the brain computes information. It may pave the way for understanding and treating neurological disorders, and for developing brain-like computers.”
The researchers also found that unlike the spikes of electrical activity generated by the somas, the dendrites could put out longer-lasting voltages that in their sum total were actually more powerful than the somatic spikes. They say the spikes are like digital computing in that they are all-or-nothing events, while the dendritic flows are akin to analog computing.
“We found that dendrites are hybrids that do both analog and digital computations, which are therefore fundamentally different from purely digital computers, but somewhat similar to quantum computers that are analog,” said Mehta. “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. Dendrites do generate digital, all-or-none spikes, but they also show large analog fluctuations that are not all or none. This is a major departure from what neuroscientists have believed for about 60 years.”
Mehta adds that the fact that dendrites are about 100 times larger in volume than somas, it’s possible that our brains have 100 times more capacity to compute information than previously believed.
“Many prior models assume that learning occurs when the cell bodies of two neurons are active at the same time,” said Jason Moore, a UCLA postdoctoral researcher and the study’s first author. “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.”
Looking at the soma to understand how the brain works has provided a framework for numerous medical and scientific questions — from diagnosing and treating diseases to how to build computers. But, Mehta said, that framework was based on the understanding that the cell body makes the decisions, and that the process is digital.
“What we found indicates that such decisions are made in the dendrites far more often than in the cell body, and that such computations are not just digital, but also analog,” Mehta said. “Due to technological difficulties, research in brain function has largely focused on the cell body. But we have discovered the secret lives of neurons, especially in the extensive neuronal branches. Our results substantially change our understanding of how neurons compute.”