The team hope the method can be refined to allow paralysed people to regain control of their own body.
The findings, published in Nature Communications, have been described as "a key step forward".
Damage to the spinal cord can stop the flow of information from the brain to the body, leaving people unable to walk or feed themselves.
The researchers are aiming to bridge the damage with machinery.
Match electrical activity The scientists at Harvard Medical School said they could not justify paralysing a monkey. Instead, two were used - a master monkey and a sedated avatar.
The master had a brain chip implanted that could monitor the activity of up to 100 neurons.
During training, the physical actions of the monkey were matched up with the patterns of electrical activity in the neurons.
The avatar had 36 electrodes implanted in the spinal cord and tests were performed to see how stimulating different combinations of electrodes affected movement.READ MORE