Neuroscientists have discovered that dendrites – branch-like projections of neurons in the brain – which were previously thought to be passive, actively process information. The discovery of this so-called mini-brain computer could provide a better understanding of neurological disorders.
Neuroscientists from University College London (UCL) in the UK and the University of North Carolina (UNC) at Chapel Hill made this discovery, which was published recently in the journal Nature, after years of research.
“Suddenly, it’s as if the processing power of the brain is much greater than we had originally thought,” says Spencer Smith, assistant professor from the UNC School of Medicine.
The team notes previous research has demonstrated that dendrites use molecules supporting electrical spikes in axons – nerve fibers that direct electrical pulses away from the cell body – to create electrical spikes themselves.
However, it was unclear whether our normal brain activity uses those spikes from dendrites. The neuroscientists found that dendrites do actively process neuronal input signals on their own, acting as “mini-neural computers.”
To demonstrate this, the two teams of scientists on either side of the Atlantic Ocean conducted a series of detailed experiments that spanned years.
By attaching microscopic glass pipette electrodes to a neuronal dendrite in the brain of a mouse, the team was able to “listen” to the electrical signalling process.
After beginning in senior author Michael Hausser’s lab at UCL, the team at UNC continued the research by recording electrical signals from dendrites in the brains of mice that were either awake or anesthetized.
Then, while the mice viewed visual stimuli on a screen, the scientists observed a strange pattern of electrical signals in the dendrites.
In effect, they found that depending on the visual stimulus the mice viewed, the dendritic spikes “occurred selectively,” showing that the dendrites were processing what the animal was viewing.
When the team filled neurons with calcium dye, they were able to record visual evidence of the dendritic spikes, revealing that dendrites fired electrical spikes while other parts of the neuron did not.
Smith notes that the spikes resulted from local processing within the dendrites:
“All the data pointed to the same conclusion. The dendrites are not passive integrators of sensory-driven input; they seem to be a computational unit as well.”
The researchers say that their findings could change the way the scientific community thinks about how neural circuitry works in the brain.
“Imagine you’re reverse engineering a piece of alien technology,” says Smith, “and what you thought was simple wiring turns out to be transistors that compute information. That’s what this finding is like. The implications are exciting to think about.”
The team from UNC plans to do further research into what this newly discovered role of dendrites might play in brain circuitry, particularly in conditions where the integration of dendritic signals may malfunction.
Spencer Smith explained to Medical News Today how his team’s findings may help the medical community better understand neurological disorders:
“It is tremendously difficult to develop treatments for neurological disorders like autism and schizophrenia, because we don’t understand how the healthy brain functions, let alone what goes wrong in those diseases. Thus basic neuroscience research, like our study, is an essential step on the long road to new treatments. This is a major motivation behind President Obama’s BRAIN Initiative.”
He added that if other future research “reveals that some diseases have dysfunctional dendritic spiking as a component, then it might be possible to develop treatments because there are many drugs that can affect the electrical activity of neurons.”