Neurolaw & The Mind

NPR News broadcast three in-depth installments narrated by Barbara Bradley Hagerty in the past three days about the latest findings on the genetic and neural underpinnings of criminal behavior and how these insights may influence sentencing in court.

The product of the gene MAOA discussed in the first installment entitled "A Neuroscientist Uncovers A Dark Secret" is the enzyme monoamine oxidase A. This enzyme breaks down the neurotransmitters dopamine, noradrenaline and serotonin. Modifications of this gene have been associated with an elevated risk for criminality (Guo and others, 2008). Persistently increased levels of dopamine may result in volatile, aggressive behavior. The research discussed in the NPR broadcast was conducted with the principal investigator's own family members and awaits publication in a peer-reviewed scientific journal. The identification of a large number of genes associated with mental disorders like autism may serve as a reminder that it is unlikely that the defect of only one gene may cause a behavior that is the result of multiple complex nerve cell interactions in the brain.

The second installment entitled "Inside A Psychopath's Brain: The Sentencing Debate" reports on evidence obtained with functional magnetic resonance imaging (fMRI) that convicted psychopaths viewing scenes with content needing moral judgment show abnormal activation of cerebral cortex. The principal investigator recently co-authored a study of similar design in which read statements were used instead of visual scenes (Harenski and others, 2010).

The identification of genes with gene chip analysis as well as the identification of activated brain regions with fMRI that may play a role in criminality are probabilistic with attached uncertainties. The third NPR News installment entitled "Can Your Genes Make You Murder?" informs us about the impact of the science discussed in the prior installments on a recent court decision in the state of Tennessee as an example of the advent of neurolaw, that is the inclusion of neuroscience in criminal law.

As intriguing as the scientific observations on the workings of the criminal brain may be, the science remains in its infancy. Examining the brains of convicted felons does not permit us to determine whether the detected changes are the result or the cause of the criminal behavior. A genetic modification statistically associated with criminal behavior may point to a potential hazard. Yet, only the committed crime provides the necessary affirmation.

Therefore, judgment in court will remain based on the offenders' decisions and actions. The difficulty of our judgment is brought into focus, however, when we are confronted with people who are perfectly able to make informed decisions and know right from wrong in every-day life, but who commit the most horrible crimes when the conditions are right with a good chance of repeating such crimes in a similar situation.

Are psychopathic offenders capable of repentance? Will incarceration improve them? Is it possible to 'cure' their affliction or will they forever remain too dangerous to be allowed to live among us unsupervised again?

These questions are as old as mankind. Whether neuroscience will help us find better answers remains to be seen.

I expressed my ambivalent feeling towards neurolaw in a poem when the term evolved into a buzz word. The poem is written in magic ink. The writing takes some time to unfold:

References

• Guo G, Ou XM, Roettger M, Shih JC (2008) The VNTR 2 repeat in MAOA and delinquent behavior in adolescence and young adulthood: associations and MAOA promoter activity. Eur J Hum Genet 16: 626-634.
• Harenski CL, Antonenko O, Shane MS, Kiehl KA (2010) A functional imaging investigation of moral deliberation and moral intuition. Neuroimage 49: 2707-2716.

Related Posts

• fMRI I: Blood Flow & Mental Processing
• Imaging Discord in the Brain
• Autism & Genes, Revisited

Imaging Discord in the Brain

The advent of functional brain imaging has revolutionized the fashion in which psychologists and psychiatrists look at the brain. The pictures of behavior-related cerebral activation provide unprecedented information leading to new hypotheses about the workings of our mind.

However, it is of utmost importance to keep in mind that non-invasive functional brain imaging methods do not allow us to record nerve cell activity directly. With positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI), the most-frequently used procedures detect changes in local cerebral blood flow while the participants are exposed to sensory stimulation or execute tasks. Brain cells need sugar and oxygen to fuel the chemical reactions necessary for information processing. Both resources cannot be stored in the brain and thus have to be delivered on demand. Hence, local blood flow increases when nerve cells are activated, resulting in a tight association between nerve cell activity and blood flow under normal physiological conditions.

The molecular mechanisms that couple blood flow to nerve cells activity are not yet fully understood. Glutamate constitutes the predominant excitatory neurotransmitter in the cerebral cortex. This neurotransmitter, its precursors and metabolites as well as its cellular receptors may play a crucial role in the coupling of the two events. However, molecules unrelated to glutamate may also be important. Nitric oxide (NO) and adenosine are known to influence the blood flow response.

In addition to our lack of knowledge on the coupling between the nervous and the vascular response, blood flow measurements inherently cover a volume of brain tissue and do not permit us to identify precisely which nerve cells drive the observed change in flow.

In this week's issue of the journal Nature, Kerri Smith informs us on new findings relevant to the interpretation of functional brain imaging. Yevgeniy Sirotin and Aniruddha Das demonstrate the consequences of the uncertainties discussed above in a letter to Nature entitled "Anticipatory haemodynamic signals in sensory cortex not predicted by local neuronal activity" (Nature 457:475-479). The authors used optical imaging for the fine-grain mapping of changes in blood flow in exposed primary visual cortex of monkeys. The animals were trained to react to a small visual cue. As anticipated, blood flow increased locally in visual cortex after stimulus onset, and the researchers could record concomitantly increased nerve cell activity with wire electrodes inserted into the brain tissue at this location.

Remarkably, blood flow also increased, when the monkeys expected the visual cue to appear, but it was not presented. The anticipation alone was sufficient to significantly increase the local blood flow. By contrast, Sirotin and Das were not able to detect any increase in nerve cell activity that could be related to the anticipatory increase in blood flow.

The apparently discordant findings may not be entirely surprising. The monkeys were accustomed to treats as reward for their participation. Their readiness for the task may have activated neuromodulatory inputs to visual cortex that remain sub-threshold under ordinary conditions and do not trigger nerve cell activity directly, but facilitate the nerve cell response to the imminent stimulus. How such sub-threshold nerve cell signals may increase local blood flow remains an open question.

The discrepancy between blood flow and nerve cell activity Sirotin and Das observed suggests that blood-flow based brain imaging data must be considered with utter prudence, when complex behaviors are examined that involve the subjects' active participation and anticipation. The findings should caution those who strive to correlate patterns of cerebral blood flow with socio-affective mental disorders and criminality in the hope of developing novel predictors for our actions.

Neurolaw is an attempt to associate patterns of brain activity with criminal behavior. Terry Gross interviewed the eminent American neuroscientist Michael Gazzaniga on this issue on National Public Radio's Fresh Air broadcast July 28, 2008. I once wrote down my thoughts on this idea in secret ink. If you wish to spare a few minutes, click on the video, let the magic unfold and enjoy!