Fig. 22.

Activity of neurons in the rostral and caudal primary motor cortex (M1), as well as spinal cord, during isometric force production. A: discharge of a spinal neuron and a rostral M1 neuron during a force production task. The force trace is shown at the bottom (in units of torque, in Newton meters). Whereas activity of the spinal neuron shows a burst, followed by tonic activity during the hold period, the M1 neuron exhibits a burst but is silent during the hold period. Force offset is marked by a green arrow. B: activity of M1 neurons, spinal neurons, and EMG averaged across all directions of force. C: activity of M1 and spinal cells aligned to force onset when target was in the preferred direction (PD). D: activity of M1 and spinal cells aligned to force offset when the center target was in the PD. From Shalit et al. (2012), with permission. E: activity of a caudal M1 neuron during isometric force production. The cell is active during the hold period. F: population averaged activity of caudal M1 neurons during isometric force production, as well as during reaching, toward PD or 180° away from PD. From Sergio et al. (2005), with permission. G: schematic model of projections from the rostral and caudal M1 cells to the spinal cord.