Body Maps: Big Hands, Tiny Butt
In your brain are a variety of “body maps” that, like roadmaps, help you navigate in the world. Without these body maps, you wouldn’t know how to peel an orange or tie a shoe, drive a car or sing a baby to sleep. Body maps allow you to do all of these things and more by relaying information (in the form of nerve impulses) about movement and touch from your brain to your body and vice versa, from body to brain.
Big Hands, Tiny Butt
A prominent feature of body maps is that they are not proportionally to scale—instead, the size of each body part represented on the map reflects the amount of brain processing power dedicated to that part. In other words, regions of the body that require more processing power take up more real estate on the map. For example:
Your hands take up a tremendous amount of space on your body map because hands must perform fine motor tasks like writing, tying your shoes, or manipulating a fork.
Your lips and mouth also occupy a lot of space on the map because speaking and swallowing are complex activities that require exquisite motor control and sensory acuity.
Your butt on the other hand takes up very little space on your body map because, well, when was the last time you used your butt to dice an onion or respond to an email? We simply don’t use our butts to perform fine motor tasks or to gather sensory information from the world.
The body maps sit on the surface of your brain, with the hands and mouth occupying a lot of space on the map—which reflects the amount of brain processing power they require to function.
It is no accident that the body parts that take up the most real estate on our brain maps also happen to be critical for survival of our species. When our ancestors started to walk upright on two legs, it freed their hands and allowed them to manipulate tools. This was a critical evolutionary moment that led to other major developments for our species. And our ability to communicate – using the highly refined movements of our lips, tongues, and mouths – helped our species live and work together in small groups and tribes.
Put another way, can you remember a single day when you didn’t use your hands or mouth? Probably not, because they are essential for survival.
The Little Man in Your Brain
Body maps were first discovered in the 1930s by a neurosurgeon named Wilder Penfield, who was treating epilepsy patients in Canada. He used electrodes to stimulate the patients’ brains and noticed that stimulating different points on the brain surface elicited different sensations or movements in different body parts. His patients, who were awake during the procedure and could communicate with him, would indicate when they felt, for instance, a tingling in a finger or noticed that their toes were wiggling. Systematically, point by point, Penfield mapped the whole human body onto the surface of the brain – one map for sensation another for movement. The resulting image, created by his team, is that of a distorted human body, with disproportionately huge hands, lips, and face.
Morphing Body Maps
A critical feature of body maps is that they are not fixed – they can change their shape and organization over time, for better or worse. With an injury or chronic pain, for instance, the map may become distorted. And with repeated practice of a skill, like dribbling a basketball or playing the flute, regions of the map become larger and more detailed.
About Amy and Kim
Amy is a Certified Advanced Rolfer® and movement educator specializing in chronic pain.
Kim is a certified manual therapist specializing in fascial manipulation and athletic recovery.
