Monkey Study Suggests Sense of Touch is a Possibility for Prosthetic Limbs
The technology behind prosthetic limbs has developed drastically over the past few years. One of the more recent technological advances was creating prosthetic limbs that can be brain powered to move. This type of technology would connect the brain and the prosthetic limb, creating a more natural gait. Even though this kind of technology has not been perfected, researchers have continued to move forward. In a new study using monkeys, researchers attempted to find a way to incorporate the sense of touch in prosthetic limbs.
"Our ability to grasp and manipulate objects relies critically on touch signals from the hand," said study author Sliman Bensmaia, a neuroscientist at the University of Chicago reported by FOX News. "Without these signals, we would have trouble performing even the most basic activities of daily living, like tying our shoes or even turning a doorknob. Furthermore, touch is critical for emotional communication we touch the people we care about. Finally, touch is very important in embodiment, in making our body feel like part of us."
For this study, the researchers decided to use rhesus monkeys because these animals have sensory systems that closely resemble the human system. The researchers identified the brain activity patterns in these animals when they touched different objects. In the first experiment, the researchers focused on the sensations the monkeys felt when they were touched on their fingers. The researchers would poke each finger and study the monkey's brain activity in response to the touches. The pokes were then replaced with electrical stimuli. The researchers implanted electrodes in the monkeys' brains and systems to collect data. The researchers found that the monkeys responded in the same way to both human touch and electrical stimulation.
"In the brain, light touches produce small, highly localized patterns of activation; stronger touches activate more neurons," Bensmaia said. "One way to activate more neurons through electrical stimulation is to increase the current, so we investigated this approach to convey information about contact pressure."
In the second part of the experiment, the researchers focused on pressure. They created an algorithm that allowed them to control electrical current that would mimic different levels of pressure. When the monkeys were touched via stimuli or artificial stimulation, they responded to the touch that had more pressure. This indicated that the artificial stimulation was effective in exerting pressure and eliciting the same sensory response in the monkeys.
The researchers believe that the use of electrical stimulation that was tested in the monkeys could be the key to creating prosthetic limbs that would give humans their sense of touch back. The researchers stated that since the brain is an extremely complex organ, more research would need to be done to target specific areas responsible for creating the sense of touch.
"In our experiments to date, we focused on the most basic information for object manipulation information about contact location, contact pressure and contact timing," Bensmaia said. "Of course, we obtain a lot more information than that from our sense of touch. We get information about object shape, size and texture; we can feel when something is moving across our skin or slipping from our grasp."
This study was published in the Proceedings of the National Academy of Sciences (PNAS).