The motor homunculus is a “little man” map that shows how the areas of the brain allocate more control over certain areas of the body, like the hands and mouth.
This “little man” is known as a homunculus, a representation of how much brain control is given to certain regions of the body. Scientists have mapped the areas of the brain that are devoted to specific areas of the body. This homunculus map is drawn from the motor cortex of the brain. The nervous system allocates brain power according to need. Regions of the body with a high level of conscious dexterity use larger areas of the brain. There is more circuitry and more neurons dedicated to those areas of the body.
For example, the homunculus hands are extra-large because a lot of the brain is devoted to the hands. Our hands are so sensitive and we do all our major feeling of things with our hands. The lips and tongue are so big because taste and speech take a lot of brain cells. Areas like elbows and knees are small because they don’t use as much of the brain. If you put something on your knee with your eyes closed, you wouldn’t be able to tell what object it is. Your hands would be able to tell though. The thumb itself is larger than the entire pelvic region.
Certain things can change the structure of your homunculus. If a person experiences a stroke, their homunculus will change shape. It may be lopsided or not have certain parts on it at all. The brain is dynamic and malleable. Practicing yoga can be one technique to alter the physical structure of the brain. Although the number of individual neurons cannot increase, the neuron pathways and connections can become more efficient. The circuitry of your brain can rapidly form between existing neurons to meet new demands. This is the basis for muscle awakening in yoga. As you gain more body awareness through yoga practice, refining the circuitry of your brain becomes a byproduct. When you advance your physical practice, your mind-body consciousness expands.
A neurosurgeon can affect the body by stimulating the brain. A yoga practitioner can begin at the other end of the nerve pathway by heightening the awareness of the body. There are some areas of the body that we use so often that the brain doesn’t have to think about the engagement. For example, your psoas muscle (deep hip flexor and core muscle) is engaged so often that it is unconscious and is very small on the homunculus. To strengthen that mind-body connection, yoga practioners can start with awareness. Be aware of what the psoas (or any other region of the body) is feeling during asana practice—is the psoas tight, tense, or open? Then the next level of consciousness is learning to engage or release the psoas, which can be enormously helpful in yoga practice. Next time you get on your yoga mat, think about how your homunculus is changing and evolving.
Breathe. Sweat. Smile. 