Where is my arm? The relative role of vision and proprioception in the neuronal representation of limb position.

A central problem in motor control, in the representation of space, and in the perception of body schema is how the brain encodes the relative positions of body parts. According to psychophysical studies, this sense of limb position depends heavily on vision. However, almost nothing is currently known about how the brain uses vision to determine or represent the location of the arm or any other body part. The present experiment shows that the position of the arm is represented in the premotor cortex of the monkey (Macaca fascicularis) brain by means of a convergence of visual cues and proprioceptive cues onto the same neurons. These neurons respond to the felt position of the arm when the arm is covered from view. They also respond in a similar fashion to the seen position of a false arm.