Two monkeys with electrical sensors in their brains learned to feed themselves with robotic arms, suggesting bionic technology may one day help restore mobility for people with disabilities, researchers said.

In the experiment, two macaque monkeys were given prosthetic arms, complete with shoulders, elbows and fingerlike grippers. The arms were linked to electrodes that transmitted signals from areas of the brain that control movement. Nerve signals powered the arms to grab marshmallows and fruit, popping them into their mouths "all in one natural-looking motion," according to the article, reported online in the journal Nature.

The study documents the first successful use of a "brain-machine interface" to control a robotic limb for a practical function, the authors said.

Before now, such experiments involved control of a cursor on a computer screen, according to the researchers from the University of Pittsburgh and Carnegie Mellon University.

"Our immediate goal is to make a prosthetic device for people with total paralysis," said Andrew Schwartz, the paper's lead author and a neurobiology professor at the University of Pittsburgh.

"The more we understand about the brain, the better we'll be able to treat a wide range of brain disorders - everything from Parkinson's disease and paralysis to, eventually, Alzheimer's disease and perhaps even mental illness," he said in a statement accompanying the article.

The researchers implanted a series of electrical probes, each the width of a human hair, into the monkeys' brains. Each sensor recorded signals from 100 nerve cells. When fed through a mathematical algorithm the researchers created to plot the animals' intentions, the monkeys quickly learned to control the robotic arms with only their thoughts.

The monkeys' real arms were restrained during the tests, the study said.

Within days, the monkeys were swinging the arms around obstacles. They learned to reach for objects and chew at the same time and shifted their heads and eyes normally without affecting the robot appendage.

The robotic dexterity offers "a heartening example of what, in due course, may be possible," John Kalaska, a University of Montreal professor, wrote in a commentary accompanying the article. "Learning could be even quicker in human subjects, facilitated by verbal instructions from a trainer."