树突是大脑中的“迷你神经计算机”

Dendrites（树突）, the branch-like projections¹ of neurons, were once thought to be passive wiring in the brain. But now researchers at the University of North Carolina at Chapel² Hill have shown that these dendrites do more than relay information from one neuron to the next. They actively³ process information, multiplying the brain's computing⁴ power. "Suddenly, it's as if the processing power of the brain is much greater than we had originally thought," said Spencer Smith, PhD, an assistant professor in the UNC School of Medicine.

 

His team's findings, published October 27 in the journal Nature, could change the way scientists think about long-standing scientific models of how neural⁵ circuitry functions in the brain, while also helping⁶ researchers better understand neurological disorders⁷.

 

"Imagine you're reverse engineering a piece of alien technology, and what you thought was simple wiring turns out to be transistors⁸ that compute⁹ information," Smith said. "That's what this finding is like. The implications are exciting to think about."

 

Axons are where neurons conventionally generate electrical spikes¹⁰, but many of the same molecules¹¹ that support axonal（轴突的） spikes are also present in the dendrites. Previous research using dissected¹² brain tissue had demonstrated that dendrites can use those molecules to generate electrical spikes themselves, but it was unclear whether normal brain activity involved those dendritic（树状的） spikes. For example, could dendritic spikes be involved in how we see?

 

The answer, Smith's team found, is yes. Dendrites effectively act as mini-neural computers, actively processing neuronal input¹³ signals themselves.

 

Directly demonstrating this required a series of intricate experiments that took years and spanned two continents, beginning in senior author Michael Hausser's lab at University College London, and being completed after Smith and Ikuko Smith, PhD, DVM, set up their own lab at the University of North Carolina. They used patch-clamp electrophysiology to attach a microscopic¹⁴ glass pipette electrode, filled with a physiological¹⁵ solution, to a neuronal dendrite in the brain of a mouse. The idea was to directly "listen" in on the electrical signaling process.

 

"Attaching the pipette（移液管） to a dendrite is tremendously technically¹⁶ challenging," Smith said. "You can't approach the dendrite from any direction. And you can't see the dendrite. So you have to do this blind. It's like fishing if all you can see is the electrical trace of a fish." And you can't use bait. "You just go for it and see if you can hit a dendrite," he said. "Most of the time you can't."

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