The primary motor cortex is part of the brain located just in front of the central sulcus in the precentral gyrus of the frontal lobe (the middle of the top of your brain). This is the area of your brain that controls voluntary movement based on input from the somatosensory cortex, the secondary motor cortex and other brain structures.

Neuroscientists using MEG scans have mapped out which body regions are controlled by which portions of the primary motor cortex. The toes are represented at the very top near the longitudinal fissure, and the rest progress along the precentral gyrus, ending with the head and throat at the lateral sulcus.

         leg .......   hand
            /       \....
           |   Your      \...   face
      toes |     Brain       \  
            \....            |    mouth
  Right frontal lobe, coronal view