Is There a Psychopathic Brain?
Early Days
In Without Conscience, Hare (p. 1)1 referred to an article that he and his students had submitted to the journal Science. The editor rejected the submission with the following comment: “Frankly, we found some of the brain wave patterns depicted in the paper very odd. Those EEGs [electroencephalograms] couldn’t have come from real people.” Actually, they came from a sample of psychopathic offenders who took part in a laboratory study of behavioral and brain responses to letter strings flashed briefly on a computer screen. The letter strings were neutral, positive, negative, and nonwords. The participant had to press a button as quickly as possible if what he saw was a word. Most participants responded more quickly, and exhibited larger and more prolonged brain responses (event-related potentials; ERPs), when the words were emotional than when they were neutral. Psychopaths, on the other hand, responded to all words as if they were neutral.
Fortunately, another major journal published the study,2 which was the first to support Cleckley’s hypothesis of a lack of integration of the semantic and affective components of psychopathic language. That is, their words lacked emotional coloring. There have been many literal and conceptual replications of this finding, using both ERPs and neuroimaging.3,4,5
Neuroimaging
In the early 1990s, Joanne Intrator, newly in charge of a brain-imaging unit at the Bronx Veterans Affairs Medical Center, and Hare’s group conducted what may have been the first imaging study of psychopathy, with substance abuse patients rated on the PCL-R as participants. Injection of a radioactive tracer allowed the researchers to determine which parts of the brain became most active during the task, based on Williamson et al.6 The results clearly indicated that psychopathic patients used relatively little emotional resources, and different parts of the brain, to process neutral and emotional words. An intriguing finding was that while processing emotional words the psychopathic patients showed unusual activation in areas of the brain associated with semantic and decision-making processes.
In the mid-1990s, one of Hare’s graduate students, Kent Kiehl—now a major player in the neurobiology of psychopathy—coordinated collaborative research among Hare’s lab, Peter Liddle in psychiatry, and Bruce Forster in radiology. The result was the first in a series of functional magnetic resonating (fMRI) studies that showed that the parts of the brain associated with emotional processing had little impact on the language, cognitions, and behaviors of psychopaths.7
Overview of Current Findings
Since these early studies, research on the neuroscience of psychopathy has exploded, and now includes the neurobiology of language, moral behavior, decision-making, reward and punishment, executive functions, response inhibition, error monitoring, emotional processing, cognitive-emotional integration, empathy, social cognition, and perspective-taking, to name but a few areas. An outline of research findings is well beyond the scope of this book. Detailed reviews of the neuroscience of psychopathy are available in a number of books and articles written for the public8,9,10, and for the scientific community11,12,13,14 (see a recent study by Espinoza et al.15).
We note that the dominant instruments for most of this research are the PCL-R and its derivatives, the PCL: SV (see Chapter 2) and the PCL: YV.16,17 Their importance stems from the fact that they are the standards for the assessment of psychopathy, but also because they each have the same four-factor structure. Why is the latter important? Because the psychopathy-neurology associations often depend on the factor involved (see review by Poeppl et al.18). The result is a more nuanced picture of psychopathy than we could obtain with total psychopathy scores alone. For example, Wolf et al.19 noted, “Moreover, the right uncinate fasciculus [the major white-matter tract connecting ventral frontal and anterior temporal cortices] finding was specifically related to the interpersonal features of psychopathy (glib superficial charm, grandiose sense of self-worth, pathological lying, manipulativeness), rather than the affective, antisocial, or lifestyle features. These results indicate a neural marker for this key dimension of psychopathic symptomatology.”
Importantly, researchers have managed to relate, in theoretically meaningful ways, many of the traits and behaviors of psychopathy to various brain structures, functions, and networks. For example, Kiehl20 has described the paralimbic system, a group of interconnected brain structures involved in emotion processing, goal-seeking, motivation, and self-control. Based on an extensive body of research, he and his colleagues have identified some of the brain structures and processing features related to criminal psychopathy. In most cases, the evidence indicates that, on average, psychopaths show decreased activity and smaller volumes in brain areas involved in emotional processing, but increased activity and greater volumes in areas related to reward and its anticipation.
Poeppl et al.21 conducted a meta-analysis of 28 fMRI studies and 155 experiments. In general, their results were consistent with those described above. The meta-analysis revealed “aberrant” brain activity associated with psychopathy converging in frontal, insular, and limbic regions: decreased activity in regions crucial for semantic language processing, action execution, pain processing, social cognition, and emotional reward processing. There was increased activity in a region for cognitive reward processing and another region associated with semantic language and pain processing. Interestingly, the increased activity in regions associated with semantic language processing is consistent with the results of early studies described above, indicating that psychopaths tend to use linguistic resources to process emotional material.
Of course, brain regions are interdependent and interactive, and an important line of research is concerned with functional circuits, networks, and connectivity. In this work, researchers measure functional connectivity during a resting state (no task), a procedure that uncovers the relations among the neuronal activation patterns of anatomically separated brain regions, and describes the organization, interrelationship, and integrated performance of functionally coupled brain regions (p. 36).22 Espinoza and colleagues (p. 2634) suggested “that the affective and interpersonal symptoms of psychopathy (Factor 1) are associated with aberrant connectivity in multiple brain networks, including paralimbic regions.”23,24,25
Attentional Models
Hamilton and Newman26 argued that the cognitive/affective models of psychopathy, discussed above, are consistent with attentional (cognitive) models in which it is possible to explain the results of behavioral and brain-imaging studies of psychopathy in terms of selective attentional processes. They present a response modulation hypothesis in which a “bottleneck” in the lateral prefrontal cortex blocks emotion and inhibitory information when the attentional focus is on goal-directed information.
A Psychopathic Brain?
So, after this long discourse, is there a psychopathic brain? Scores of empirical studies with offenders, many of which show the same things, suggest that there is something different about the structure and function of the brains of psychopaths, at least at the group level. (Many psychopaths show the anomalies described above, but many others do not.) We believe that, as a group, they are wired up differently, but for reasons that are unclear. Most researchers use terms such as damaged, dysfunctional, or deficit, whereas it is possible that the differences are not evidence of deficit but of adaptive evolutionary processes. Certainly, it is difficult to understand how high-functioning psychopathic executives might be the product of erroneous, faulty wiring of the brain. Moreover, this raises an important issue that we cannot address at this time. Are the structure and functioning of the brains of psychopathic corporate and other professionals similar to those of psychopathic offenders?
Neurolaw
These issues are not simply academic. They have serious implications for determining legal culpability and responsibility. There already has been at least one attempt to use imaging as a mitigating factor in a death penalty hearing.27,28 The attempt failed, but the legal and scientific arguments will continue for a long time.29,30,31