Final answer:
The fingers have the greatest amount of motor cortex dedicated to them due to the required precision for fine motor skills, more than the knees, trunk, or arms.
Step-by-step explanation:
The primary motor cortex is responsible for planning, controlling, and executing voluntary motor functions. The motor cortex controls various parts of the body with different regions of its map dedicated to specific muscle groups. According to the motor homunculus, which is a visual representation of the body within the brain, different body parts are allocated space in the motor cortex based on the complexity and preciseness of the movements they can perform. The amount of brain tissue in the motor cortex devoted to each part of the body is proportional to how intricate the movements of that body part are.
The fingers require highly precise movements with fine motor skills for tasks such as writing or playing a musical instrument. Therefore, the neurons responsible for the musculature of the fingers occupy a large amount of space in the lateral face of the motor cortex. The fingers have much more cortical space dedicated to them compared to less dexterous parts of the body like the knees or trunk, which perform broader, more powerful movements. Consequently, the fingers are the part of the body associated with the greatest amount of brain tissue in the motor cortex.