CNT researchers in the GRID Lab at the University of Washington are answering basic neuroscience questions for clinical and rehabilitative applications. Their work is also informing the development of adaptable brain-computer interface systems that can respond to an end user’s specific needs. In this article, learn about one of the GRID Lab’s research studies that deepened the understanding of how hand and finger movements are connected to the brain.
In April 2019, the Center for Neurotechnology (CNT)-affiliated GRID Lab at the University of Washington (UW) published a research paper titled “Context-dependent relationship in high-resolution micro-ECoG studies during finger movements.” In this paper, researchers wanted to see if there were statistically significant differences in thumb movement, finger movement and a synergistic pinch motion, which requires both finger and thumb movement.
This paper studied the pinch finger motion in three patients with epilepsy, a neurological disorder characterized by seizures, sensations and loss of awareness. Kaitlyn Casimo, doctoral candidate researcher in the GRID Lab at the time of the study and current Training and Outreach Specialist at the Allen Institute, said that the lab focused on “pinch” because it’s a common hand movement that would need to be understood when creating a hand prosthetic.
“You could test a different grip for grabbing a piece of paper or grabbing a canister,” Casimo said. “There are lots of different positions that you can put your hand in that involves those two fingers.”
One unique aspect of this research was the use of micro-electrocorticography (micro-ECoG), an electrophysiological technique that measures brain signals in the motor cortex with three times higher resolution than standard ECoG. This non-invasive technique allowed researchers to record data from fewer neurons when classifying finger movements.
“The goal of the study was to evaluate the limits of spatial resolution of ECoG in terms of representation of dexterous hand movements,” said Jeremiah Wander, a former CNT-affiliated graduate student, researcher in the GRID Lab and researcher in Microsoft Research’s Medical Devices Group. “Specifically, we wanted to contrast the sensitivity of the micro-scale ECoG grids in detecting individual finger movements to that of the standard scale grids used in clinical seizure mapping.”
Based on the micro-ECOG measurements, the thumb movement during the pinch motion was markedly smaller than the neural signal during thumb movement alone. This suggests that there was a non-linear relationship between the brain signal and the motor output for some hand movements, a result that Casimo did not expect.
“When you're doing any experiment, the first person you have to prove your results to is yourself,” Casimo said. “Once you've proven to yourself that the data are sound, you start brainstorming other ways to approach the question and [understand the results].”
Taking an interdisciplinary approach to research
Wander said that this research project was an interdisciplinary effort that drew on the knowledge of multiple generations of graduate students in the GRID Lab. While Dr. Jeff Ojemann, the principal investigator of the GRID Lab, conducted the surgeries in patients, Tim Blakely, a former research fellow in the GRID Lab, designed the experimental protocol. Additionally, Dr. Chao-Hung Kuo, a former research fellow in the GRID Lab and the UW Department of Neurological Surgery and current attending physician at the Department of Neurosurgery in the Taipei Veterans General Hospital, brought his awareness of anatomical structures in the brain. Casimo focused on statistical data analysis, and Wander focused on the signal processing.
“The process of collecting data from the human brain during an awake craniotomy, … is a striking example of interdisciplinary research,” Wander said. “It requires the coordination of the complete surgical team with technical research teams to collect the data, run the analyses and interpret the results.”
Translating an understanding of the brain in future research
By supporting the understanding of human motor representations of hand movement, this paper aligned with the GRID Lab’s goal of answering basic neuroscience questions for clinical and rehabilitative applications. Research from this paper also informs neuroscience research and the development of adaptable brain-computer interface (BCI) systems that respond to an end user’s specific needs.
“By having this basic research that says, ‘here's how the brain behaves in this particular condition,’ it empowers the next generation of researchers to take that knowledge and ask, ‘what can I do or engineer with that knowledge?’” Casimo said.
Long-term, this study can support the development of a prosthetic or re-enervate a muscle after spinal cord injury.
“Regardless of what your actuator is, whether it's a hand or a prosthetic like a robotic arm, you would need to be able to detect the intent to move from the brain and decode it,” Casimo said. “This is part of that decoding for index finger and thumb.”
Dr. Kuo said that this research paper supports insights that could inform future BCI development.
“To help the patients with spinal cord injuries, I hope there will be a platform integrating all clinical information, including brain signals and peripheral signals, to improve the patient's clinical outcomes,” Kuo said.
Learn more about the GRID Lab’s research and current projects on their website.