Behold, the bizarre homunculus.
The sensory receptors in our body are distributed unevenly. Receptors are densely concentrated in areas where high acuity and fine movements are needed, such as the fingertips, and sparse in other areas where a superior sensory distinction is not necessary, such as the back. This creates a distortion of our body in our brain, making our fingers look extremely larger than our backs in the eyes of our cortex.
These maps are CONSTANTLY changing in response to our environment and what we are exposed to. For example, if we were to cast our arm and stop using our hand altogether, our cortical representation of that hand would shrink. In comparison, if we begin to provide touch cues and drive awareness to certain areas of our body, we can increase the representation of that area of the brain, allowing for greater control and awareness of that area.