Daniel Moran, PhD
Daniel Moran, PhD, associate professor of biomedical engineering in the School of Engineering & Applied Science and of neurobiology in the School of Medicine at Washington University in St. Louis, Missouri, has recently completed a set of experiments with MD/PhD student Adam Rouse that refines the control of a brain-computer interface (BCI). The study has implications for prosthesis users and those who suffer from spinal cord injuries.
The research builds on the 2006 work Moran and collaborator Eric Leuthardt, MD, a Washington University neurosurgeon at Barnes-Jewish Hospital, St. Louis, conducted with an intractable epilepsy patient who learned to play the video game Space Invaders through thought alone. A video of the test subject shows him wiggling his fingers to get the cursor to move, but the behavior soon fell away as the patient’s brain adapted and instead of imagining “wiggle fingers,” the boy imagined “cursor right.”
A 32-channel epidural electrocorticography (EECoG) grid, the product of a joint effort between Moran and Justin Williams, associate professor in the College of Engineering at the University of Wisconsin, Madison, is small enough to fit within the boundaries of the sensorimotor cortex of the brain (inside the skull, but outside the dura mater). Researchers plan to slip the thin, flexible grid under a macaque monkey’s skull and to train the animal to control a computational model of a macaque arm by thought.
The virtual arm will have seven degrees of freedom-rotation about the shoulder joint, flexion and extension of the elbow, pronation and supination of the lower forelimb, and flexion, extension, abduction, and adduction of the wrist-compared to the two degrees of freedom that operated the Space Invaders’ cursor in a two-dimensional plane. Persuaded by a virtual-reality simulator to treat the virtual arm as its own, the monkey will then be asked to trace with its virtual hand three circles that intersect in space at 45 degrees to one another. Because this task better separates degrees of freedom, scientists will be able to map out cortical activity to details of movement more easily.
Should the experiment prove successful, Moran will then connect his BCI to a new peripheral nerve-stimulating electrode under development with MD/PhD student Matthew R. MacEwan. In collaboration, the two devices would allow a paralyzed arm to move because the mind is sending signals to peripheral nerves that stimulate muscles to expand or contract.
In the latest round of experiments, Moran sought to define the minimum separation between electrodes that preserved independence of control. “So now that we know how many electrodes we can pack into an area, we have some idea how many degrees of freedom we’ll be able to control,” he said in a university press release.
“I like doing basic research, and I want to continue to do basic research,” Moran continued, “but I also really want to solve the problem and help people. Someone’s got to get the technology translated to the marketplace, so we’re trying to do that as well.”
