Dendrites, the branch-like projections of neurons, were once thought to be passive wiring in the brain. But researchers at UNC-Chapel Hill have shown that the dendrites do more than relay information from one neuron to the next. They actively process information, multiplying the brain’s computing power.
“Suddenly, it’s as if the processing power of the brain is much greater than we had originally thought,” said Spencer Smith, Ph.D., an assistant professor in the UNC School of Medicine.
His team’s findings, published October 27, 2013, in the journal Nature, could change the way scientists think about long-standing scientific models of how neural circuitry functions in the brain, while also helping researchers better understand neurological disorders.
Axons are where neurons conventionally generate electrical spikes, but many of the same molecules that support axonal spikes are also present in the dendrites. Previous research using dissected brain tissue had demonstrated that dendrites can use those molecules to generate electrical spikes themselves, but it was unclear whether normal brain activity uses those dendritic 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 input 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 microscopic glass pipette electrode, filled with a physiological solution, to a neuronal dendrite in the brain of a mouse. The idea was to directly “listen” in on the electrical signaling process.
Published October 30, 2013.