Motor cortex

The part of the cerebral cortex, including the primary motor cortex and adjacent areas of the frontal lobe, that generates commands for movement, connected directly to the motoneurons of the spinal cord as well as indirectly to other so-called motor structures such as the basal ganglia and the cerebellum via the thalamus (see figure below).  It was Gustav Th. Fritsch (1836-1927) and Eduard Hitzig (1838-1907) in 1870 who together established the motor cortex as fundamental to motor control, which they reported as a paper entitled ‘On the electrical excitability of the cerebrum‘.  They did so by applying an electrical current to the precentral gyrus of a dog, and found they could elicit specific movements depending on the location of the stimulus.  These connections (or hodology) are schematically represented in the figure below. There is a debate about how the motor cortex ‘codes’ movements.  Evidence from non-human primates suggests that populations of cortical neurons code the direction of movement (the ‘population vector hypothesis‘), but this is open to another interpretation, namely, that coding is for the target.  Another suggestion is that populations of neurons code for force of movement.  While these two suggestions appear to be competitors, it may be the case that they are not mutually exclusive.