Easier Way to Study Brain Electrical Activity Could Advance Prostheses

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In a paper published in July in the journal Neuron, Krishna Shenoy, PhD, and a team of neuroscientists at Stanford University report that they have established a simpler way to study the brain's electrical activity that could one day open the door to potentially wireless brain sensors that would bring thought-controlled prosthetic devices into wider use.

In the paper, the team explains how it has circumvented the current process of tracking the activity of individual neurons in favor of decoding neural activity in the aggregate. Each time a neuron fires it sends an electrical signal, known as a spike, to the next neuron down the line. "Each neuron has its own electrical fingerprint and no two are identical," said Eric Trautmann, PhD, a postdoctoral researcher in Shenoy's lab and first author of the paper. "We spend a lot of time isolating and studying the activity of individual neurons."

The process is called "spike sorting," and must be done for every neuron in every experiment, an endeavor that consumes much of a researcher's time annually and is expected to become more so as scientists build implants with greater numbers of electrodes.

To record the activity of many neurons without the complexity of spike sorting, the researchers borrowed a theory from statistics that suggested how they could uncover patterns of brain activity even when several neurons are recorded on a single electrode. They then demonstrated their approach experimentally. They used a new type of electrode that was designed to pick up brain signals in mice and adapted this technology to record the brain signals of rhesus monkeys. They recorded hundreds of neurons at the same time and showed that they could get an accurate portrait of the monkey's brain activity without spike sorting.

The researchers believe their work will ultimately lead to neural implants that use simpler electronics to track more neurons than ever, and also more accurately. In addition, the new electrodes, coupled with the sampling algorithms, should eventually be able to record brain activity without the many wires needed currently to carry signals from the brain to the computer that controls the prosthesis, Trautmann said.

"This study has a bit of a hopeful message in that observing activity in the brain turns out to be easier than we initially expected," said Shenoy, the Hong Seh and Vivian W.M. Lim Professor of Engineering, and senior author of the paper.

Editor's note: This story was adapted from materials provided by Stanford University.