The Psychopath Inside by James Fallon

close up, far away—is mapped onto the cortex in the upper part of the posterior area, called the superior parietal cortex. People with damage to this brain area on one side will ignore the other half of their sensory world. So they may only perceive the numbers on the left side of a clock dial, but not the right side. Given ablank circle, they will fill in the numbers on the dial from 1 to 12, but these will all be drawn on just one half of the clock. If the damage is done to the hemisphere that controls their nondominant hand, let’s say the right superior parietal cortex for a right-hander (each hemisphere controls the opposite side of the body), then they will go the extra step in their “agnosia.” They will be able to move the opposite leg, and feel a pinch on that leg, but they may ask the doctor or nurse to remove the leg from the hospital bed because it is foreign and doesn’t belong to their body.
    Another function of this posterior area is the understanding and conceptual creation of language. In the dominant hemisphere (the left side if you’re right-handed), this language function enables us to master syntax and grammar, while in the nondominant hemisphere, this language function allows us to understand the song and rhythm of language, as well as humor. It appears that the dominant hemisphere function is more genetically determined, while the nondominant hemisphere function is more molded by environment. That is, you will learn to mirror the accents and cadence and patois of speech from your family and friends, but your basic ability for grammar and syntax is more genetically determined. One tends to adopt the song and rhythm of speech around the time one reaches puberty, but the range and capabilities of individuals vary widely. In the case of Henry Kissinger and his younger brother, Walter, who fled Nazi Germany in 1938, when Henry was sixteen and his brother was fourteen, the elder brother kept his pronounced Frankish accent while Walter sounded very American.
    In the Rubik’s Cube middle sector of the hemisphere, there are the somatic and motor areas that map the skin senses in the back half of this middle piece, and the map of the areas that control the muscles of the body. Just in front of this motor cortex is the premotor cortex, which is involved in the planning of motor movements and in learning the rules of how we swing a golf club and play the piano. These two motor-related cortices form a strip on each hemisphere in size and placement like the support arms of a set of earphones.
    The anterior, or front, section is the prefrontal cortex and is responsible for the so-called executive functions of the brain, including knowing rules, making plans, and enabling short-term memory. This “scratch pad” memory lasts seconds or tens of seconds and helps us to remember phone numbers long enough to dial them and tells us, without looking, where we set our drink while we’re eating or playing poker. The prefrontal cortex is the brain region most important for the elaboration of personality and character, and the control of impulse, obsessions, and antisocial behavior.
    Besides being the locus of will, the prefrontal cortex is related to a myriad of functions we consider particularly well developed in primates, especially humans. These involve what has been called “memory of the future,” that is, projecting one’s mind into the future to imagine, or experience, really, how one will remember an act that has not yet taken place. This is akin to the pleasant sensation one has when playing a game of chess and knowing that after just five moves one will cream his opponent. This knowledge of the imagined future resides in a circuit centered in the prefrontal cortex.
    I suspect that humans’ ability to do this relies, in part, on a mutation in the gene for catechol-O-methyltransferase, or COMT. This enzyme is responsible for breaking down dopamine in the frontal