PROVIDENCE, RHODE ISLAND — A new study published in the journal Scientific Reports, provides evidence that neurons in the middle frontal gyrus — a part of the brain’s frontal lobe — may play a role in planning body movements, but only when those movements are in response to auditory stimuli.
The findings represent what could be a previously unknown function for this part of the brain and could provide a new target for researchers developing assistive devices for both movement and hearing disorders.
The work was part of the BrainGate clinical trial, which studies a tiny investigational implant capable of recording information directly from the brain and using that information to drive the movement of computer cursors or even robotic prosthetic devices.
“One of the opportunities afforded by the BrainGate clinical trial is that at the same time as we’re working toward helping people with paralysis, we’re also learning new things about the human brain,” said Dr. Leigh Hochberg, a neurologist, professor of engineering at Brown University and director of the trial and BrainGate consortium. “This finding turned out to be a complete surprise, which is exciting.”
New Insights into Brain Function
Up to now, brain-computer interface (BCI) implants like BrainGate have mostly been placed in the motor cortex, a part of the brain associated with voluntary movement. But researchers are interested in harnessing additional signals for BCIs by exploring other parts of the brain, including areas that may be involved in the upstream planning of movements and actions. It was in the process of looking at a new brain region for BCI recording that the researchers made this new discovery.
“There’s a large body of literature to suggest that parts of the premotor cortex toward the front of the brain — the region we were looking at in this study — become active earlier than the more posterior regions of motor cortex during movement tasks. If we’re able to record signals from these areas, it’s possible that we could even further speed the responses of our neural interface system. That’s what we were investigating.”
–Carlos Vargas-Irwin, PhD, Assistant Professor of Neuroscience at Brown University and study co-author
For the study, a clinical trial participant with paralysis in his arms and legs from a spinal cord injury was asked to perform a simple movement-related task: after observing a shape in the corner of a computer screen, he would attempt to grab it and move it to the middle when cued. This was first done while the participant was being monitored by fMRI, a non-invasive method of studying brain signals in real time.
The fMRI data suggested that a specific part of the premotor cortex — located in the middle frontal gyrus — seemed to be active during the task.
The next step was to implant a BrainGate microelectrode array near that part of brain in the same participant and repeat the attempted movement task. But to the researchers’ surprise, the array detected no informative signals during a repeat of the movement task.
“We expected, based on the fMRI data, that we’d see some related activity,” said Hochberg, who also directs the Veterans Affairs Rehabilitation Research and Development Center for Neurorestoration and Neurotechnology. “So it was puzzling, to say the least, when we didn’t.”
That’s when the study took yet another unexpected turn. When the team looked at data from a related research session — one in which they verbally told the participant which target to reach for — suddenly the array picked up a strong signal from the middle frontal gyrus.
“That’s when our puzzlement turned to pleasant surprise,” Vargas-Irwin said.
It led the team to design new research that alternated between giving auditory cues and visual-only cues. That work helped to confirm that — at least in this participant — neurons in the middle frontal gyrus produced movement-related signals only in response to auditory clues.
“It was as if these neurons simply weren’t interested in visual information. But they reliably responded to auditory information, and that was completely unexpected.”
–Dr. Leigh Hochberg
The researchers caution that this was research involving a single participant, so more work needs to be done to confirm and generalize the findings. But the study does suggest a new target to be explored in pursuit of improving neural interface devices.
**Read the full story on Brown University’s website