The Psychopath Inside by James Fallon Page A

lobe after it has been released. There are two possible versions of the mutation, which, taken together, are referred to as the valine-methionine polymorphism. The methionine version of the gene leads to the production of a COMT enzyme that has a lower melting point, while the valine version codes for a COMT with a higher melting point. All this means is that, in those with the methionine version, COMT inactivates faster at normal brain temperature, allowing dopamine to hang around synapses triggering neuronal function for a longer period of time, since there is no enzyme to break down the neurotransmitter. The steady supply of dopamine enhances frontal lobe activity, including its capacities to brainstorm and premeditate. Thanks to this and other neurotransmitter-related mutations millions of years ago, early humans could plan further ahead and anticipate future events like war and famine. And because they could anticipate these events, they did things like invent weapons and learn to farm. Likewise, memory of the future allows us to appreciate a sense of time and helps explain our belief in religion, the afterlife, and eternity.
    The next way we can slice the brain’s hemispheres is into upper, middle, and lower thirds, more correctly referred to as the dorsal, intermediate, and ventral streams.
    The upper, or dorsal, stream lies right under where you wear a ten-gallon hat. This “stream,” so called by Leslie Ungerleider ofthe National Institute of Mental Health, is primarily concerned with processing “where” things are in your external environment, as well as their movements. The lower, or ventral, stream processes “what” things are in your external world, especially in the visual system. The intermediate stream codes for “when” things happen, but is also involved intimately with language and the mirror neuron system (explained in chapter 7).
    The dorsal part of the prefrontal cortex and its interconnecting subcortical areas are associated with “cold cognition,” emotionless processing of thoughts, perceptions, short-term or executive memories, plans, and rule-making. This involves both generating these thoughts and also inhibiting other thoughts, depending on established rules for success and failure in the appropriate context. Life is full of rules and contingencies, whether in Scrabble or golf or business, and the dorsal prefrontal cortex tells you when it’s okay to act on your urges—when you should place a tile or hit a ball or buy a stock—and when you shouldn’t. The lower, or ventral, part of the prefrontal cortex, largely made up of the orbital cortex and ventromedial prefrontal cortex, is involved in similar functions, but more those enabling and disenabling “hot cognition”—emotional memory and socially, ethically, and morally programmed behaviors. Someone with a highly functioning dorsal prefrontal system would have superior planning and executive functions, whereas someone with a highly functioning ventral prefrontal system would have superior control over impulsive and inappropriate interpersonal and social behaviors. Likewise, lower functioning in these systems leads to not only a lack ofcomprehension of these high-order behaviors, but an inability to control them under socially inappropriate circumstances.
    Connecting with others involves both cold (rational) cognition, where one person understands what others might be thinking and what an appropriate response might be, and hot (emotional) cognition, where one can experience empathy with another’s feelings and attitudes—that is, actually “feel” them much like the other person would experience them. Someone with damage to the hot system, let’s say in the orbital cortex, might not be able to predict others’ thoughts but will have the most trouble sharing his feelings. A dichotomy may exist between empathy, a fundamental connection with the pain of