Dark Side: Mad Man Mind

 

PET (positron emission tomography) scan is a tool used in radiology to determine the functioning of the body, specifically small areas the size of a grain of sand in tissues and organs. It is particularly useful in looking into organs, such as the brain, that are encased in bone. The PET scan is considered a functional rather than merely structural scan because it measures the functioning of the brain. Radioactive molecules that interact with the brain in specific ways are injected before the scan. They can be sugars, to measure the brain’s metabolism, or drugs that link to the receptors for various neurotransmitters, to measure the distribution of those receptors.

 

In this scan the doctors used an isotope of fluorine, F-18, bound to a type of glucose taken up by active brain cells. It remains in the cells and emits positrons, a form of radiation, for about an hour. The glucose is injected into a vein in the subject’s arm, and then the subject is slid onto a gurney into the PET scanner until the head is surrounded by the detectors. The amount of time the “photograph” of the brain is taken depends on the half-life of the isotope. In the case of F-18 this exposure time is thirty minutes, so the image that is obtained is a snapshot of brain activity that occurs in this thirty-minute period. During this time, the F-18 releases positrons that immediately collide with electrons, resulting in a release of energy detected in the coils surrounding the head in the PET scanner. The scanner’s computer software locates the source of all of the collisions, and is then able to reconstruct a 3-D image of them in the entire brain. We assign colors to the density of collisions, indicating use of glucose, and thus brain activity. The darker the area, the harder that part of the brain is working.

 

So the doctors at the scan and saw, compared to a healthy brain, a decrease of activity in the orbital cortex and the area around the amygdala. In a healthy brain, this area prevents impulsivity (i.e., it inhibits behavior), so when it is turned off, the person is impulsive. The sicko’s lawyers then told the judge that as a matter of biology, their client couldn’t control himself, and he received life without parole instead of the death penalty.

 

To better understand exactly what we saw in these scans and why it was so relevant, you first need to have a basic understanding of the human brain. The brain is organized in a bewildering number of ways, even to a silverback neuroscientist. The researcher Floyd Bloom once called it an “electrified jelly,” which is certainly what it seems like to a first-year medical student. Neuroanatomists categorize themselves into “clumpers” and “splitters” based on how they like to organize the brain. Clumpers prefer to simplify the brain into as few sections as possible, while splitters divide the brain into thousands of pieces, all with their own Latin or Greek names. To make things even more confusing, splitters like to throw into the mix the name of the scientist who first described that brain area, so we end up with names like “Zuckerkandl’s fasciculus,” “the ventral tegmental relay zone of Giolli,” and the “nucleus reticularis tegmenti pontis of Bechterew.” This is one of the reasons medical students are terrified of their first course in neuroscience. When these brain areas, their connections, chemistry, and circuitry, are considered together for any adaptive behavior, for example an infant expressing fear at the sight of a stranger, the complexity of the brain’s wiring can start to get out of hand. For clinical sciences the representation of the relevant wiring of the brain can quickly send one packing to the nearest pub for a cold one. For example, here is a “simplified” version of the brain circuitry involved in depression.

 

“Everything should be made as simple as possible, but not simpler.” Everyone is familiar with the idea that we have a left brain and a right brain. But this conception is woefully lacking in some important ways. On the next page is a drawing of the side of the brain at the top left, a view of the top of the brain looking down from above, and a view of the medial portion of the brain that you would see if you sliced the brain down the middle.

 

 

 

The most posterior region of the cortex is dedicated to the visual sensory system, as well as “association” cortices that have functions more complicated than simple seeing or touching or hearing, but rather cognitive tasks such as spatial processing. The external world—up, down, left, right, 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 a blank 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 righthanded), 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.

 

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.

 

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 of comprehension of these high-order behaviors, but an inability to control them under socially inappropriate circumstances.

 

A dichotomy may exist between empathy, a fundamental connection with the pain of others and arising very early in life, and “theory of mind,” a more elaborated medial prefrontal system that allows us to consider others’ thoughts and beliefs, even if they’re different from our own. People with autism lack theory of mind but not empathy, while people with psychopathy lack empathy but not theory of mind. Without empathy you can still have sympathy, though—the ability to retrieve emotional memories, including those that can predict what painful event is probably about to befall another person, and the will to help that person. These brain circuits mature at different times during development, and although there are major maturational events that take place in the terrible twos, puberty, late adolescence, the twenties, and the mid-thirties, some are not completely integrated until one is in the sixties, which appears to be the typical average peak time of human insight, cognition, and understanding in many realms of life.

Acknowledgements:

www.politie.nl  and a Chief Inspector – Mr. Henk van Essen©

www.aivd.nl       AIVD – Mr. Erik Akerboom ©

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