Using your feet like hands can cause organized “hand-like” maps of the toes in the brain, suggests a study of two professional foot painters led by the Plasticity Lab at University College London.
These findings, published in Cell Reports, demonstrate an extreme example of how the human body map can change in response to experience.
“Our study demonstrates an extreme example of the brain’s natural plasticity, as it can organize itself differently in people with starkly different experiences from the very beginning of their lives,” the study’s senior author, Dr Tamar Makin (UCL Institute of Cognitive Neuroscience), who leads the Plasticity Lab, comments, in a media release from University College London.
The Plasticity Lab seeks to gain more understanding of how brains are malleable in order to develop ways to tap into the brain’s innate plasticity, which may inform new rehabilitation approaches or treatments for phantom limb pain.
“For almost all people, each of our fingers is represented by its own little section of the brain, while there’s no distinction between brain areas for each of our toes,” the study’s lead author, PhD student Daan Wesselink (UCL Institute of Cognitive Neuroscience and University of Oxford), notes.
“But in other non-human primate species, who regularly use their toes for dextrous tasks like climbing, both the toes and fingers are specifically represented in their brains. Here, we’ve found that in people who use their toes similarly to how other people use their fingers, their toes were represented in their brains in a way never seen before in people,” he adds.
The two study participants are among three professional foot painters in the UK who paint holding paintbrushes between their toes. They also use their toes regularly for everyday tasks such as dressing themselves, using cutlery and typing. To do what most people would do with their two hands, both artists typically use one foot for highly dextrous tasks while using the other foot to stabilize.
Their distinctive experiences extend beyond behavior, the release adds. By not regularly wearing enclosed footwear, the foot painters get more complex touch experiences on their toes. This may also have impacted brain development of these organized toe maps.
For the study, funded by Wellcome and the Royal Society, the foot painters (as well as 21 people born with two hands, who served as a control group) completed a series of tasks testing their sensory perception and motor control of their toes.
The participants then underwent ultra high-resolution fMRI brain scanning of the brain’s body area — the somatosensory cortex. While inside the scanner, a researcher tapped the toes of the study participants, first looking for activity in the foot area of the body map.
In the foot painters, specific sections of the brain’s foot area clearly reacted to their toes being touched. Brain maps comprised of individual toes were seen for the artists’ dextrous foot, with a similar but less pronounced pattern was evident in their stabilizing foot. The two-handed controls showed no such maps. Other analyses showed the foot painters’ feet were represented in the brain in a “hand-like” way, but not the control participants’ feet.
The researchers also found that the foot painters’ toes were additionally represented in the part of their brain that would otherwise have served their missing hands. This corresponds with another study from the same lab finding that the brain’s hand area gets used to support body parts being used to compensate for disability, such as the lips, feet or arms of people who were born with only one hand.
Perhaps surprisingly, motor tasks showed the foot painters were not any better than controls at wiggling one toe at a time, but they did have heightened sensory perception for their toes compared to controls, the release explains.
[Source(s): University College London, Science Daily]