Murderous Minds (12 page)

If the brain had a figurehead like a ship, Brodmann area 10 would be it, positioned at its foremost point. The contributions of this part of the brain are poorly understood. It, however, is known to have extensive connections to other regions implicated in psychopathy and higher mental functions. These include the temporal pole (Figure 9), the cingulate cortex (Figure 10), and other parts of the prefrontal cortex (Figure 8). Besides having a role in other executive functions, the neurons seated at the very front of the brain—along with other regions (Figure 7)—may play a role in moral decision-making.

A more recent study by Martina Ly,
et al.
reported that 21 psychopathic criminal inmates had thinner cerebral cortices in half a dozen or so different regions of the brain compared to incarcerated non-psychopaths.
¹¹
These and other studies “strongly reinforce the suggestion that psychopathy is a neurobiological condition,” according to psychopathy expert R. J. R. Blair of the National Institute of Mental Health in Bethesda, Maryland.
¹²
Cortical thinning reported in psychopathy and conditions such as schizophrenia, depression, posttraumatic stress disorder, attention-deficit/hyperactivity disorder, and autism could be due to fewer neurons, smaller neurons, fewer connections between neurons, abnormalities affecting glial cells, or some combination of these.

Estimates of the average number of neurons in a healthy person range from 10 to 200 billion. A recent study suggests that there are 86 billion neurons, and a similar number of brain cells called glia, neuroglia, or glial cells—give or take 8 or 10 billion.
¹³
Glia were once thought to serve as glue (glia in Greek) holding neurons in place. Now we know they are essential
partners in nervous-system function because they modulate and support neuronal activity.
¹⁴
They have been neglected by researchers who, for most of the history of neuroscience, have concentrated their attention on neurons.

To add another level to the complexity of the central nervous system, there are many different types of glial cells and neurons. Neuroscientists aren’t even sure how many different types of neurons there are in the mammalian brain, because they often have features that make it difficult to categorize them reliably and authoritatively.

However you want to categorize neurons, overall there probably are at least 100 trillion points of contact—communicating connections called synapses—between these cells. Again, no one knows exactly how many connections they make, but it’s safe to say there are many more combinations of connections than there are stars in the Milky Way galaxy, a comparatively wimpy 400 billion. There may be one billion synapses in just one cubic millimeter of cerebral cortical brain tissue; that’s how complex a marvel the human brain has evolved into. Even the computers at the National Security Agency are dullards compared to a moderately intelligent human brain. They, together with smart phones, tablets, and fMRI machines, are merely useful tools developed by more impressive human brains for their own purposes.

As staggering as brain-cell statistics are—and they are still staggering even for many scientists who have spent their careers studying the brain—it nevertheless is possible to observe thinking, feeling brains by sliding people into devices such as fMRI machines. This significant technical breakthrough in the field of neuroscience does not mean, however, that scientists can now identify locations in the brain where thoughts and feelings originate or are located. Although many press reports of brain imaging studies imply, outright suggest, or mistakenly assume that they can, the science behind brain scans is more subtle—and limited—than that.

The goal in studies such as the one for which Willem and others with high PCL–R scores volunteered is to compare activity and responses in the brains of psychopaths to activity in the brains of non-psychopaths. The comparisons are made when the subjects are presented with images and other stimuli designed by researchers to detect differences in brain function in the two groups. One group, the controls, knows what a conscience
is. The other group of individuals knows as much about a conscience as a person born without sight knows about the color red.

In 2000, German scientists were the first to apply fMRI technology in the study of psychopathy.
¹⁵
Frank Schneider, M.D., Ph.D., at the University of Düsseldorf and his fellow researchers compared a dozen men between the ages of 18 and 45 years with an average PCL–R score of 29 to a dozen psychologically healthy men. They showed their 24 subjects pictures of faces with neutral expressions. They paired the faces with either a puff of room air (a neutral stimulus) or a puff of rotten yeast odor (an aversive stimulus). Neither group liked the rotten smell; they both learned to associate smells with the pictures of the faces. The difference between the two groups appeared in the fMRI images when they were learning to make these associations. The non-psychopaths showed decreased activity, while the psychopaths showed increased activity in regions of the brain closely involved in emotional responses: the dorsolateral prefrontal cortex and the amygdala. The authors suggest that the increased activity in these regions observed in psychopaths might reflect greater effort to make an emotional association between a bad smell and a particular face. It is as if the neuronal processing mechanism devoted to learning this task with an emotional component (“I hate that smell”) is more efficient in non-psychopaths compared to psychopaths. Specific brain cells involved in emotional processing in psychopaths may have to work harder to make the association.

Since 2000, thousands of criminals—mostly in the United States, but also in Willem’s home the Netherlands, the United Kingdom, Finland, Germany, and other nations—have volunteered to have their brains scanned. Once escorted from their cells to a lab equipped with a scanner, they lie flat on their backs on a slab, which is a couple of feet wide. For the experiment to produce usable information, they must be still; movement will blur the results, so their heads are held in cushioned restraints or headrests. After their upper bodies are slid into the long donut-hole opening in the center of the device, the noise starts. The banging, vibrating, magnet-bearing mechanism pounds out industrial-strength noise as the volunteers try to complete mental tasks devised by the investigators who study this subset of humanity in an attempt to find the source of their antisocial and—in the opinion of most people—evil behavior. The researchers believe
their results reveal functional deficits in the brains of criminal psychopaths.

These deficits and abnormalities are thought to mirror the emotional deficiencies that characterize people with this extreme type of personality—or, according to many, this type of personality disorder.

fMRI technology is complex and logistically cumbersome, yet the actual scan is the result of the exploitation of the simplest atom, hydrogen. This minimalist element has just one electron moving around one positively charged proton. Outside an MRI machine, protons in hydrogen atoms spin about randomly. That changes when they are inside a functioning MRI machine; this is where the magnetic part of magnetic resonance imaging becomes essential. The randomly spinning protons snap to attention in response to the powerful electromagnetic field generated by the MRI machine. Under the influences of this field, the protons flip en masse into an aligned state.

The MRI machine then sends a radio wave that snaps the protons back to their usual randomly oriented states. This sequence of events wouldn’t be much help in providing a picture of the brain except for one thing: when the protons flip back to their usual state of randomness, they emit a kind of echo in the form of radio waves. These mini-broadcasts announce to a detector in the MRI precisely where the protons are located.

Thanks to the complex calculations of mathematicians and the efficient coding of computer programmers, the “echoes,” or proton-generated signals, are turned into three-dimensional images of the brain. Denser brain matter has more hydrogen nuclei than less-dense material and will thus broadcast more signals. The contrast between dense and less-dense brain tissue, darker and lighter, produces MRI images such as those in Figures 3 (bottom), 5, 12, and 13.

The result is a potentially valuable collection of relatively detailed anatomical pictures that can show the brain from different angles. The noisy but painless process of having an MRI can reveal tumors and aneurisms and structural abnormalities of the brain. It can just as easily produce images of other organs and reveal the presence of cancer, blood-vessel anomalies, damaged nerves, shredded muscle, and other health problems. All the while, it avoids the health risks associated with radiation from X-rays or radioactive materials.

From Here to There and Back Again: DT-MRI

MRI technology isn’t just for taking static, high-tech, 3-D X-ray-like pictures. It has been adapted to provide specialized tools for studying specialized structures in the brain. One, called Diffusion Tensor Magnetic Resonance Imaging, or DT-MRI, is useful for studying connections in the brain, the communication pathways that allow the brain to function.

Disconnecting your prefrontal lobes from the rest of your brain, for example, may disconnect you from your former joie de vivre and much of your personality. This consequence was established after Egas Moniz received the 1949 Nobel Prize for pioneering the use of frontal lobotomies. Physicians used the simple new surgical technique to treat people with schizophrenia and other then-untreatable mental disorders, as well as some individuals who simply displayed troubling behavior. The prize-winning psychosurgery, worked out and popularized shortly before the development of effective antipsychotic drugs, left thousands mentally maimed. This most tragic and embarrassing episode in neurology, however, at least revealed the essential role that the connections between the frontal lobes and other parts of the brain play in higher mental functioning.

A brain structure like the amygdala, for example, which figures prominently in neurobiological investigations of psychopathy, needs its connections to the frontal lobes to work effectively. The amygdala just isn’t the amygdala unless it’s part of a neural circuit. The same is true of other brain structures. The amygdala has mistakenly been portrayed in the news media as a “center” of fear, anger, or aggression, depending on the story of the day. In fact, it is a small but highly influential structure that is active when you experience something that is immediately interesting or important. Subtleties like this are not that difficult to convey in the media, but they aren’t as catchy as erroneously portraying the structure as a key center that controls our basic instincts like aggression and sex.

DT-MRI provides a way to examine pathways in the brain such as the one linking the amygdala to the prefrontal cortex by taking advantage of the fact that water molecules jiggle. Pour a little milk into your tea or coffee and you can appreciate that the suspension spreads out or diffuses in your cup. Water molecules in cells, and in their extensions like the long projections of neurons called axons, diffuse. In something that is long and
narrow like an axon, water molecules will diffuse more along the length of the structure than along its cross-section. Imagine a Ping-Pong ball in a pipe. If the ball moves steadily, you can bet it is likely to move along the length of the pipe and not bounce up and down in one place across its narrow width.

DT-MRI detects the motion of hydrogen in water molecules as they move along the length of the tract. Long structures like muscles, tendons, and ligaments are good subjects for DT-MRI. So are nerve fiber tracts in the brain. These extensions, axons, carry electrical signals to other neurons in other parts of the brain. The axons are surrounded by a fatty, white insulating substance called myelin, provided by glial cells. That’s why fiber tracts in the brain are called white matter. Areas rich in neurons are called gray matter (although it actually looks more pink than gray). Processing the data produced by a DT-MRI scan can result in striking three-dimensional images of nerve pathways in the living brain. Take a look at Figure 6 to get an idea of the potential of this approach for illuminating brain structure.

If water in a structure such as a nerve fiber bundle moves about randomly—if it is as likely to go in one direction as another—the bundle gets a score of zero. If movement is highly directional, then the bundle gets a score of 1. Physicists call this score fractional anisotropy (FA). (The word anisotropy is used when something depends on direction. The opposite, isotropy, is used when something is independent of direction.) FA is influenced by the health of nerve fibers, their density, their size, and their insulation. FA provides an indirect indication of the health or structural integrity of a bundle of nerve fibers connecting one part of the brain to another.

A practical drawback of the MRI technology is posed by the powerful magnet encased in the MRI machine. It is so powerful that it will rip any metal object you take near it through whatever is holding it. Magnetic field strength is measured in units called Tesla. The 7-Tesla magnet in the MRI at the University of Oxford Centre for Functional Magnetic Resonance Imaging of the Brain could pick up a double-decker bus.
¹⁶
Magnets of one Tesla can pick up cars, and they do just that when used in junkyards. Most MRI scanners have 1-to 3-Tesla magnets. It’s important, therefore, not to forget if you have had metal implanted anywhere in your body before you have an MRI. A pacemaker, a skull plate, or a pin holding together a

fractured bone, for example, will disqualify you from the procedure and inconvenience you considerably if you were to forget. Other than that, the only potential drawbacks of the procedure are the expense ($500 or so for a session) and the patience a patient or subject must muster as the machine takes 20 to 45 minutes to scan the brain or most other parts of the body.