What happens to the brain when you paint with your feet?
The incredible case of two toe artists born without hands. When feet in the brain are represented like hands.
This painting is called “Flower Explosion” and is the work of artist Tom Yendell. He is like many other passionate artists and has been drawing ever since he can remember, but one thing is definitely different about him: He was born without both arms. This was the result of the drug Thalidomide which his mother had taken during pregnancy. Despite this visible disability Tom is incredibly optimistic and says that “his life has been no different than any able-bodied counterparts; except that he has had to adapt to do every task with his mouth, feet or chin” (Yendell). It is both humbling and intriguing to think about the challenges and adaptations Tom has undergone throughout his life and to wonder how radically different he must have been exploring the world around him.
At least that is what a group of neuroscientists from University College London (UCL) thought. They wanted to find out more about the effects this excessive foot usage, experienced by toe artists like Tom, might have on the way their brains are organized. For this aim they devised a study with Tom and Peter Longstaff, another foot artist born without hands and recruited through the Mouth & Foot Painting Artists Collective. Amongst other things, the researchers focused on the foot and (missing) hand areas on the outer layer of the brain, the so-called somatosensory cortex, where sensory information from these corresponding body parts is processed. Nowadays it is well-established scientifically that individual parts of the body are very distinctly represented along this strip of cortex and interestingly the hands have a particularly detailed map, with individual fingers occupying their very own bits of cortical territory (Kaas et al., 1979). In other words, touching any of your fingers will send signals to activate a cluster of brain cells in a distinct location of the somatosensory cortex, which is adjacent to but can be clearly distinguished from the activation patterns evoked by any other finger. Importantly though, the maps of other body parts such as the feet and their individual toes are far less distinguished than the hand map in the brains of most humans (Akselrod et al., 2017). This makes sense if you think about the very pronounced usage of your individual fingers, for instance to type on a keyboard or pick up small coins, as compared to the primitive role our individual toes play in daily life. But this is quite the opposite for Tom and Peter. So, what does it look like in their brains?
The research team from UCL outlined their approach to this question and their findings in a comprehensive report (Dempsey-Jones, Wesselink, Friedman, & Makin, 2019). They used functional Magnetic Resonance Imaging (fMRI), a very sophisticated neuroimaging technique that captures blood flow as an indirect measure of neuronal activation, to obtain very detailed scans of Toms’ and Peters’ brain and the activation patterns in response to passive touches of their feet. Unlike the age-matched control group included in the study, the two foot-artists revealed distinct toe maps in the somatosensory cortex by showing clearly selective clusters of brain cells responding to touch on four out of five toes. This was especially pronounced on the foot they use most in daily life. Interestingly, the location and basic macroscopic organization of these toe maps in the brain visually resembled those found in other species with similarly persistent use of their feet, like monkeys (Liao et al., 2016).
To obtain a more comprehensive idea of the compensatory behavior and repertoire of toe movements the two artists utilize in daily life, Dempsey-Jones and colleagues also used qualitative questionnaires. These revealed remarkable toe dexterity and striking behavioral adaptations such as using the toes to write, use a computer or feed oneself with cutlery. The researchers suspect that Tom and Peters’ toe selectivity and remarkable sensitivity to cutaneous sensory input is also in part due to a life largely spent without footwear. Another very interesting finding was obtained from examinations of the brains (missing) hand area. The functional scans demonstrated that representations of the toes are significantly more hand-like in the foot artists than in the control group.
When it comes to such major changes in the brain, the researchers emphasize the role of critical time periods to the extent of adaptation. Studies with amputees who have lost their arm later in life, for instance, have shown the persistence of hand representation in the sensorimotor cortex despite many years of not using the missing hand (Kikkert et al., 2016; Wesselink et al., 2018). In terms of behavioral adaptation, typically developed adults could not be trained to use their individual toes in the same way as Tom and Peter (Friedman and Goodman, 2016). The development of such distinct toe maps in the brain and these remarkable compensatory motor skills still seems quite exclusive to the experience of upper-limb loss before birth or in early childhood. This introduces a very interesting new idea, namely that we might all have a genetic predisposition for designated toe maps in the somatosensory cortex of our brain (Tsanov, 2019). But unlike our monkey friends, we get used to wearing socks and shoes as soon as we can walk and, therefore, we no longer receive the specialized sensory input necessary to maintain a distinct map of our toes. Crucially then, when Tom and Peter started using their feet persistently in order to explore the world around them it was at such an early stage in their life, that the body maps in their brains were still developing. Tom remembers already painting at a very young age, together with his artistic sister (Diep, 2019), and according to Peters’ recollection “when he was little, his mother encouraged him to pick things up with his feet and taught him to write by putting crayons in his toes. He started school, at age five, already able to scribble his name with his right foot” (Diep, 2019).
