The Relationship Between Sensation and Action

Last week, I was reading about sensory receptors in my textbook: Principles of Neural Science. My inner yogi found it fascinating that somatosensory and motor systems are closely organized within the brain. This means the regions responsible for touch sensation are closely tied with the regions for movement.

This relationship is so strong that it often occurs completely independent of the brain, handled in a decentralized process called a “reflex”. These are moments when touch sensation demands action so quickly that there is no time to consult the central command system. These reactionary systems jolt our hands away from hot surfaces, our feet off of sharp objects, and protect our organs from being crushed when our belly is sat on.

There are receptors in our joints, muscles, and tendons which track position and force to trigger reflexes. The system acts like a well designed Rube Goldberg machine. Pressure on the receptor cracks open an ion channel which allows electricity to flow into a sensory neuron. That activity triggers a cascade of perfectly arranged neurons to fire, like falling dominos until they release the correct chemicals to the correct locations to activate precise musclular activity required to protect against damage. All of this without ever consulting the brain!

Interestingly, these receptors do not contribute to our internal sensation of position and muscle activity. Studies have asked people where they think their body is while measuring neural activity in the body and in the brain. They find that neural activity in the bodily receptors don’t predict our perceived position as well as activity in the motor cortex, the part of the brain responsible for muscle activation. This means internally generated signals to muscles determine how that muscle will feel. It is our effort on the world that defines our perception of it. My inner yogi was thrilled. Yoga can be viewed as the sustained attention on the effortful action of multiple muscles. This grounds me in my body because this is exactly how my brain learns where my body is!

The relationship between sensation and action are inextricably tied and make up the foundations of our nervous system. As you move throughout your life, remember that your body is designed to interact physically with its environment. The fact that the mind has emerged from such a system means your psychology also benefits from being grounded by action. Next time you have a yoga session, you can think about how your mental awareness of your body is determined by your actionable command of your body. Use this knowledge to inspire your fluid relationship with the world around you :)

With love,

Michael