The project, detailed in the journal Nature Communications, involved training rats to recognize a visible light source and poke at the source with its nose to get a sip of water. Then electrodes were implanted in a region of the rats’ brains that is associated with whisker-touching. The electrodes were connected to an infrared sensor on the rats’ heads, which stimulated the target neurons when the rat was facing the source of an infrared beam. Then the visible lights in the test cage were replaced by infrared lights.
It typically took about four weeks of practice for the rats to figure out how to use their new infrared sensory system, but eventually the rats could respond to the invisible light as well as they responded to the visible light. Presumably, they could “feel” where the infrared flash was coming from, as part of their whisker-touching sense.
Nicolelis said the experiment showed that the brain is “much more plastic than we thought” when it comes to adapting to new stimuli.
That plasticity is the key to another set of experiments he and his colleagues have been conducting with rhesus monkeys, in which the monkeys learn to use their brain waves to control robotic arms or manipulate virtual objects on a computer screen. Over the years, Nicolelis’ research team has developed a brain-cap system for monkeys that can pick up neural signals in almost 2,000 channels simultaneously, and send them wirelessly to a computer for processing. Nicolelis indicated that he was closing in on the goal of creating a system that could control a full-body exoskeleton.
“We can get animals to control the whole body now, when you get to the 1,000-neuron margin,” he said.
Such work feeds into the Walk Again Project, a multinational effort to develop next-generation, full-body prosthetics for people with disabilities. Nicolelis wants to have an experimental brain-controlled exoskeleton ready in time to make its debut at next year’s World Cup soccer finals, which are to be hosted by Brazil, Nicolelis’ native country.
“We hope we will open the World Cup with a paraplegic young adult walking onto the field,” he said.
**Coleman, meanwhile, is working on ways to make brain-control devices less obtrusive. He is among several researchers who have been developing stamp-sized wireless sensors that can be worn like temporary tattoos. Such sensors can be used to monitor a person’s medical signs — but if they’re worn on the head, it’s possible to pick up brain waves. In fact, Coleman found that the wireless tattoo sensors worked as well as the conventional, wired stick-on electrodes.
The results suggest that someday, it might be possible to develop a computer program to read the brain-wave patterns sent in by a tattoo on your forehead, and then fine-tune a virtual character to respond as if it was reading your thoughts**.