Homunculus

In Light Sonata, Baxter helps Charlie understand Rupert’s madness at the piano by pulling out a model of Penfield’s homunculus like the one shown above. The clues relate to the big hands and big face relative to the rest of the body—and to the phenomenon of phantom limbs. 

After a limb is amputated, many patients continue to feel them. How can that be? In an excerpt from Phantoms in the Brain: Probing the Mysteries of the Brain, author Ramachandran says:

 Of the many strange images that have remained with me from my medical days, perhaps none is more vivid than that of the deformed little man you see [below] draped across the surface of the cerebral cortex—the so-called Penfield homunculus. The homunculus is the artist’s whimsical depiction of the manner in which different points on the body’s surface are mapped onto the surface of the brain – the grotesquely deformed features are an attempt to indicate that certain body parts such as the lips and tongue are grossly overrepresented.

The map was drawn from information gleaned from real human brains. During the 1940s and 1950s, the brilliant Canadian neurosurgeon Wilder Penfield performed extensive brain surgeries on patients under local anesthetic (there are no pain receptors in the brain, even though it is a massive nerve tissue). Often, much of the brain was exposed during the operation and Penfield seized this opportunity to do experiments that had never been tried before. He stimulated specific regions of the patient’s brain with an electrode and simply asked them what they felt. All kinds of sensations, images, and even memories were elicited by the electrodes in the areas of the brain that were responsible could be mapped. 

This “sensory homunculus,” as it is now called, forms a greatly distorted representation on the surface of the brain, with the parts that are particularly important taking up disproportionately large areas. For example, the area involved with the lips or with the fingers takes up as much space as the area involved in the entire trunk of the body. This is presumably because your lips and fingers are highly sensitive to touch and are capable of very fine discrimination, whereas your trunk is considerably less sensitive, requiring less cortical space. For the most part, the map is orderly though upside down: the foot is represented at the top and the outstretched arms are at the bottom. However, upon close examination, you will see that the map is not entirely continuous. The face is not near the neck, where it should be, but is below the hand. The genitals, instead of being between the thighs, are located below the foot. (page 25).

Giant hands? Giant face? Making them capable of finer discrimination than other parts of the body? 

Since most artists use either the hands or face as the source of their creation, perhaps the discriminations in art arise from discriminations in our neurology—a clue that brings Baxter to the nuances of the hand, face, and phantom limbs that allow him to help Charlie with Rupert’s madness at the piano.