As humans, we have three areas of support to help keep us upright with gravity. Our eyes, ears, and feet.
Eyes
We can see through our eyes with peripheral vision and focal vision. The sensorimotor activity needed to keep us upright takes place in the sub-cortical part of the brain, which is our peripheral vision. Peripheral vision is the “where” aspect of seeing. Sub-cortical vision sees blurry edges, black and white, and has a sense of whole and of movement.
Focal vision uses the cortical part of the brain. The “what” aspect of seeing is the focal vision. The cortical vision sees art, shape, and space orientation. We need to use both peripheral and focal vision to keep us balanced and aware of our surroundings.
Ears
The inner ear is also in the sub-cortical part of the brain, which is the most ancient part of the brain. The otolitaic system in the inner ear senses gravity and allows us to orient, move, and assume postures. The vestibular nerves in the otolitaic system are the first nerves to myelinate after we are born because they are essential for survival. The vestibular nerves transmit sound and equilibrium information from the inner ear to the brain. We have to orient our movement in the gravity field before we can nourish ourselves with food.
Feet
The feet move and sense through mechanoreceptors. These mechanoreceptors receive information as we move. They notice temperature, texture, and pressure. Our feet can notice an uneven surface that may cause us to fall before the rest of our body notices. Try walking around barefoot more often!
Each of the three sides in the “Triangle of Support” keep us oriented and upright in gravity.