The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics (Oxford Landmark Science)

by Roger Penrose

The right somatosensory cortex deals with sensations from the left-hand side of the body, and the left, with the right-hand side. There is a corresponding region of the frontal lobe, lying just in front of the divison between the frontal and parietal lobes, known as the motor cortex. This is concerned with activating the movement of different parts of the body and again there is a very specific correspondence between the various muscles of the body and the regions of the motor cortex. We now have a ‘motor homunculus’ to depict this correspondence, as given in Fig. 9.4. The right motor cortex controls the left-hand side of the body, and the left motor cortex, the right-hand side. Fig. 9.2. The left-hand field of vision of both eyes is mapped to the right visual cortex and the right-hand field of vision to the left visual cortex. (View from below; note that the images on the retina are inverted.) Fig. 9.3. The ‘somatosensory homunculus’ graphically illustrates the portions of the cerebrum – just behind the division between frontal and parietal lobes – which, for various parts of the body, are most immediately concerned with the sense of touch.

It is not left eye to right cortex, it is the left field of vision in both eyes that match to the right cortex