The human brain has an extraordinary ability to adapt to major changes, both in the brain itself and in the rest of the body. New research in the journal Cell Reports shows that for individuals born without hands, a lifetime of using one’s feet to do precise tasks reshapes the brain in profound ways, creating uniquely specialized divisions that can be seen with brain imaging technologies.
In a paper published on Tuesday, a study comparing two foot artists to typical controls (people born with hands) shows that the region in the artists’ brains associated with the sense of touch for their feet was divided into precise sections associated with each toe. The same area in a group of typical controls’ brains, on the other hand, did not show much differentiation. This adaptation looks a lot like the hand region in the brains of individuals who were born with hands, which show similar maps for fingers.
But the unique attributes of these artists’ brains didn’t end there.
The area of the foot artists’ brains that’s normally associated with hand control showed a significant level of correlation with their feet. The researchers write that this indicates the artists’ brains appear to have adapted to accommodate the absence of hands.
“This result demonstrates that toe-related activity in the missing hand area is at least loosely organized and that this organization mirrors native hand organization features,” writes the team, led by co-lead authors Harriet Dempsey-Jones, Ph.D., a neuroscience teaching fellow at University College London, and Daan Wesselink, a doctoral candidate at the University of Oxford.
As shown in the video at the top of this article, these artists paint with their feet. This includes sketching, handling tubes of paint, wielding brushes, and everything else a painter does. Beyond painting, they perform most of their daily tasks with their feet, so functionally, their feet fulfill the same role that hands do for those who were born with hands.
Previous research on the brain’s somatosensory cortex, the main part of the brain that receives signals associated with the sense of touch, has shown that it contains detailed maps of the fingers. Knowing this, the team investigated whether the foot artists’ dexterous toes had similar maps. By studying the somatosensory cortex in each foot artist’s brain, they observed for the first time that indeed this was true. For the typical controls, there was an area in the somatosensory cortex associated with the feet, but it was not divided up into specific sections associated with the toes.
Previous research on amputees and individuals born without certain limbs has shown that bodily experiences early in life play a major role in how the brain interacts with limbs. For instance, individuals who have a limb amputated later in life still maintain an active region of their brain associated with the limb.
“Conversely, people with congenital unilateral limb loss show no organized finger representation for their missing hand,” write the study’s authors.
But as this latest study shows, individuals born without arms can compensate with their feet, and their brains can reorganize in remarkable ways to support this adaptation.
Abstract: Although the fine-grained features of topographic maps in the somatosensory cortex can be shaped by everyday experience, it is unknown whether behavior can support the expression of somatotopic maps where they do not typically occur. Unlike the fingers, represented in all primates, individuated toe maps have only been found in non-human primates. Using 1-mm resolution fMRI, we identify organized toe maps in two individuals born without either upper limb who use their feet to substitute missing hand function and even support their profession as foot artists. We demonstrate that the ordering and structure of the artists’ toe representation mimics typical hand representation. We further reveal ‘‘hand-like’’ features of activity patterns, not only in the foot area but also similarly in the missing hand area. We suggest humans may have an innate capacity for forming additional topographic maps that can be expressed with appropriate experience.