This week's article is focused on "Control of Wrist and Arm Movements at Varying Difficulties" by Jason Boyle. Our muscles are controlled by “motor units”, which each consist of a neuron, and the muscle fiber(s) it activates or “innervates”. The muscle that responds is termed an “effector”. Brain mapping studies have shown that a disproportionate area of the motor cortex governs certain effectors of the body.