Two artists who paint with their toes have unusual neural footprints in their brains. Individual toes each take over discrete territory, creating a well-organized “toe map,” researchers report September 10 in Cell Reports.
Similar brain organization isn’t thought to exist in people with typical toe dexterity. So finding these specialized maps brings scientists closer to understanding how the human brain senses the body, even when body designs differ (SN: 6/12/19).
“Sometimes, having the unusual case — even the very rare one — might give you important insight into how things work,” says neuroscientist Denis Schluppeck of the University of Nottingham in England, who was not involved in the study.
The skills of the two artists included in the study are certainly rare. Both were born without arms due to the drug thalidomide, formerly used to treat morning sickness in pregnant women. As a result, both men rely heavily on their feet, which possess the dexterity to eat with cutlery, write and use computers.
The brain carries a map of areas that handle sensations from different body parts; sensitive fingers and lips, for example, have big corresponding areas. But so far, scientists haven’t had much luck in pinpointing areas of the human brain that respond to individual toes (although toe regions have been found in the brains of nonhuman primates). But because these men use their feet in unusually skilled ways, researchers wondered if their brains might represent toes a bit differently.
The two artists, along with nine other people with no special foot abilities, underwent functional MRI scans while an experimenter gently touched each toe. For many people, the brain areas that correspond to individual toes aren’t discrete, says neuroscientist Daan Wesselink of University College London. But in the foot artists’ brains, “we found very distinct locations for each of their toes.” When each toe was touched, a patch of brain became active, linking neighboring toes to similarly neighboring areas of the brain.
The finding was enabled by using a particularly powerful MRI machine that had the strength to reveal the relatively small and hard-to-see toe maps, Schluppeck says.
Researchers don’t yet know when this map in the brain gets drawn, or whether intense toe training might allow people to create toe maps in their brains — an idea that draws skepticism. Wesselink suspects that the artists’ toe maps were created very early on, and sharpened over decades of sophisticated toe use. “When you use your body in a different way, from very young, your brain develops differently,” he says.
Dan Feldman, a neuroscientist at the University of California, Berkeley, describes the mark that the toes leave on the brain as a kind of sensory autobiography. “Here, these two individuals had a particularly unique sensory experience, and one can see the trace of that in their brains.”