Brain power used to control prosthetic arm

In the summer of 2004, Tim Hemmes took his motorcycle out for a typical mid-July ride in his… In the summer of 2004, Tim Hemmes took his motorcycle out for a typical mid-July ride in his hometown Butler, Pa. Unexpectedly, a deer ran out in front of him, and he swerved to avoid hitting the animal. Hemmes hit a mailbox and fell onto a guardrail.

That night Hemmes was flown to UPMC Mercy Hospital. He said he technically died twice on the flight.

When Hemmes woke up in a hospital room, he tried to scratch an itch on his nose. It was then that he realized he could not move his arm. The accident had rendered 23-year-old Hemmes paralyzed from the neck down.

Seven years later, Hemmes now has hope that he might use his arms again: He’s the first human to participate in the particular type of prosthetic-arm research lead by Andrew Schwartz, a professor of neurobiology in Pitt’s School of Medicine. The research started on monkeys a couple of decades ago.

Hemmes said that he got involved in the research after a physician in Schwartz’s neurobiology department referred him to the team. Schwartz and his team of four have developed a prosthetic arm that can move based on a user’s thoughts.

Jennifer Collinger, the co-investigator on the human side of the research project and assistant professor at Pitt in the Department of Physical Medicine and Rehabilitation, said that she and the team have been preparing to test the arm on a human for the past four years. The device was designed with amputees in mind.

The team surgically implanted an electrode in August that contained 32 sensors on the top of Hemmes’ motor cortex, the part of the brain that controls movement. Wires from the electrode run from his brain down to his collarbone where they surface and are connected to the computer.

Using electrococleography, or ECoG, the team records Hemmes’ brain activity on the computer wired to a prosthetic arm that has not yet been attached to Hemmes’ body.

Collinger and her team serve as the “middle men.” When Hemmes thinks to move a part of his body, the team can read his brain waves shown on the computer screen and move the corresponding part on the prosthetic arm.

The team and Hemmes developed different signals for movement. For instance, when Hemmes wants to move his thumb to the right, he thinks about moving his thumb. But, when he wants to move this thumb to the left the thinks about moving his elbow. The team is trained to interpret the brain waves differently.

“I wouldn’t say [moving the arm] was hard. I just had to train myself,” Hemmes said.

Because the Federal Drug Administration has only approved the study for 29 days, Hemmes had to get the surgery twice: once to implant the electrode and once to remove it. Once the team moves into the next phase, Hemmes will be the primary candidate for testing. Hemmes said that he worked on using the arm for four to six hours every day. He felt mentally exhausted after practicing to tell the computer how he wanted his arm moved.

When it came to participating in the study, Hemmes said he went into it with “good anxiety.”

“I don’t know if a paralyzed man can shake, but I was shaking,” Hemmes joked.

Collinger said that the operation went smoothly and Hemmes experienced no adverse effects.

She believes it will be another five to 10 years until the arm is made available to the public. The research team wants to work on making the arm wireless before releasing it to the general population.

Currently, one downside to the prosthetic arm is that it allows the user to touch objects, but he or she cannot feel them. To improve the naturality of the arm, the team is working on adding sensors to the prosthetic.

The FDA has approved the team to conduct another study in which an electrode will be implanted in the brain for a year. This electrode will do the same as Hemmes’, but it penetrates the surface of the brain. It has not yet been used in humans, but Collinger and her team are recruiting volunteers.

“The robotic arm is fantastic. It can help a lot of people like amputees…. I still have my arms. I want my movement back,” Hemmes said.

Although Hemmes felt no sensation when operating the prosthetic arm, he said that did not make a difference when he got to hold his girlfriend’s hand for the first time. The two started dating after his accident.

Hemmes said that on the last day of the research, before the electrodes were removed, his girlfriend asked him to hold her hand.

“I put my robotic palm against hers. She started to cry. I started to cry because she was crying,” he said. “I’ve never been able to hold her.”

Hemmes said that the last person he held was his 18-month-old daughter. And he hopes for her to be the first person he holds again.

“She will be the first person I wrap my arms around again, and I’m never going to let go,” Hemmes said.