The scientist --life inspiring innovation muscle bound

09.2018 | THE SCIENTIST 19

Notebook

NEWS AND ANALYSIS

PAUL

MARASCO, LABORATORY FOR

BIONIC INTEGRATION

Muscle Vibes

W

hen Amanda Kitts’s car was

hit head-on by a Ford F-350

truck in 2006, her arm was

damaged beyond repair. “It looked like

minced meat,” Kitts, now 50, recalls. She

was immediately rushed to the hospital,

where doctors amputated what remained

of her mangled limb.

While still in the hospital, Kitts dis-

covered that researchers at the Reha-

bilitation Institute of Chicago (now the

Shirley Ryan AbilityLab) were investi-

gating a new technique called targeted

muscle reinnervation, which would

enable people to control motorized pros-

thetics with their minds. The procedure,

which involves surgically rewiring resid-

ual nerves from an amputated limb into

a nearby muscle, allows movement-

related electrical signals—sent from

the brain to the innervated muscles—to

move a prosthetic device.

Kitts immediately enrolled in the

study and had the reinnervation surgery

around a year after her accident. With

her new prosthetic, Kitts regained a func-

tional limb that she could use with her

thoughts alone. But something impor-

tant was missing. “I was able to move a

prosthetic just by thinking about it, but I

still couldn’t tell if I was holding or letting

go of something,” Kitts says. “Sometimes

my muscle might contract, and whatever

I was holding would drop—so I found

myself [often] looking at my arm when

I was using it.”

What Kitts’s prosthetic limb failed to

provide was a sense of kinesthesia—the

awareness of where one’s body parts are

and how they are moving. (Kinesthesia

is a form of proprioception with a more

specific focus on motion than on posi-

tion.) Taken for granted by most people,

kinesthesia is what allows us to uncon-

sciously grab a coffee mug off a desk or

to rapidly catch a falling object before it

hits the ground. “It’s how we make such

nice, elegant, coordinated movements,

but you don’t necessarily think about it

when it happens,” explains Paul Marasco,

a neuroscientist at the Cleveland Clinic in

SEPTEMBER 2018

I’VE GOT A FEELING: Amanda Kitts takes part

in a test of a prosthetic designed to recreate

a user’s sensation of limb movement.