Neuroscientists take baby steps towards better prosthetics

Advanced neuroprosthetics, with the potential to restore touch, movement, and sight, are not going to happen this year – or five years from now – but they are coming.

Advanced neuroprosthetics, with the potential to restore touch, movement, and sight, are not going to happen this year – or five years from now – but they are coming. These efforts were recently highlighted at the Society for Neuroscience conference in Washington, DC. In a press conference titled Advances in Neuroprosthetics and Robotics Enrich Lives, researchers from four institutions outlined their efforts to use emerging technologies to restore function.

Moderated by Dr. Leigh Hochberg, professor of engineering at Brown University and Director, Center for Neurotechnology and Neurorecovery, MGH Neurology, the first presentation was by Collin Kaufman a graduate student in the Gillette lab at the University of Illinois, Urbana-Champaign. Kaufman discussed the team’s efforts to understand how neural signals get delivered to muscle.

Researchers developed an interface between spinal and muscle tissue, creating a neuromuscular junction in a dish. With this model, they could study how the muscle responded to glutamate and other chemicals. For example, fibers moved when exposed to glutamate and stopped when treated with muscle-inhibiting drugs. 

“This system has neuron and muscle components that can respond to an external stimulus and generate an actuated force – it can locomote, it can move,” said Kaufman in a news release. “The next step is trying to attach one of these devices to an actual living thing, seeing if they can control it themselves.”

Sofia Sakellaridi, a postdoctoral researcher in the Andersen lab at the California Institute of Technology, discussed how the brain adjusts to a changing computer interface.

The researchers implanted a 96-electrode array in a volunteer’s anterior interparietal cortex, which controls movement planning, and taught her to control a cursor with her thoughts. As she learned, the lab added complications, adjusting the computer’s responses to her neural signals. While the participant could adjust to minor changes (perturbations), she could not overcome larger adjustments.

“Parietal cortex can learn to compensate for perturbations by adopting new cognitive strategies; however, these abilities have limits,” said Sakellaridi at the news conference. “So, it is likely the brain needs more training time or cannot generate new activity patterns to adapt to perturbations…The ultimate goal is to find the best brain areas to control prosthetic devices.”

Jose Fernando Maya-Vetencourt, a research scientist in the Benfenati lab at the Instituto Italiano Di Tecnologia, presented the team’s organic retinal prosthesis, made from photosensitive polymers and silk. The lab tested the prosthetic in a rat model of retinitis pigmentosa, the most common form of heritable blindness. After 30 days, the animals exhibited retinal electrical activity and started avoiding light.

“The experimental findings obtained so far highlight the possibility of developing a new generation of fully organic, highly biocompatible, low-cost and functionally autonomous photovoltaic prostheses for sub-retinal implantation to treat degenerative blindness,” said Maya-Vetencourt in a news release.

Perhaps the most impressive presentation was from Jacob Anthony George, a graduate student in the Clark lab at the University of Utah. The researchers are trying to equip prosthetics with a sense of touch to help amputees feel more connected to their prostheses and reduce phantom pain and anxiety.

In the study, an amputee tested a prosthetic hand he could control with his thoughts. In addition, electrode implants in his arm provided sensation from his missing hand. A short video showed him pushing open a virtual door with a virtual hand.

“Oh my God,” he said. “I just felt that door.”

It was an emotional moment, but these advanced prosthetics are still a long way off.

“A lot of the participants helping in the study will eventually be able to see it become a technology in their lifetime,” said George at the news conference. “There are some big engineering challenges that still need to be overcome but in a decade, maybe two, we’ll have these types of devices available.”

Photo: nambitomo, Getty Images