Switching Off Anger With an Electrode

Research on how energizing neurons with a weak scalp electrode suppresses anger.

Posted Jan 07, 2019

Source: Pixabay-

Devonte Washington, 15, was waiting on the platform of a Washington DC Metro subway station with his mother and two sisters headed to a barber shop to get a haircut for Easter Sunday church service. The young man glanced up at a stranger, 17-year-old Maurice Bellamy, who instantly took offense—pulled out a .38 caliber pistol and shot Devon to death. Three weeks earlier, Bellamy had murdered an off-duty Secret Service agent in a robbery. The teenage gunman had a long history of extreme impulsive anger and violence, which his family tried to control through appropriate medication and counseling, but to no avail. This week Bellamy was sentenced to 65 years in prison for the two murders. The judge reduced the sentence from the 80 years the prosecution requested because Bellamy was a minor at the time of the crimes.

This tragic example, like many others that fill the daily news, highlights the obvious fact that much violent crime is committed by individuals with a short fuse, males primarily, who are prone to bursts of pathological anger and violence which ultimately leaves only one option—removing such people from society permanently. New research is identifying the neural circuits of anger and aggression, and the findings offer new hope of understanding how violent impulses are triggered and suppressed in normal individuals, and how abnormalities in these circuits can result in pathology.

New methods to modulate electrical activity in brain circuits, by passing a weak DC current into the brain through the skull, together with functional brain imaging (fMRI), are bringing about new understanding of the biological basis of anger and aggression, and, in experimental studies at least, providing a new approach to control anger and aggression by directly manipulating electrical activity in these circuits.

A study just published in the journal Cortex by Gadi Gilam and colleagues at Tel Aviv University reports that anger and aggression can be suppressed by targeting a specific region of the brain by using weak direct current stimulation through the skull. Using the technique of transcranial direct current stimulation (tDCS), an electrode is placed on the forehead, and a weak DC current (1.5 mA) is delivered for 22 minutes. There are no obvious effects of switching on this voltage to the forehead, but neurons in the brain beneath the positive pole of an electrode will become more excitable. Conversely, electrical activity in neural circuits beneath a negative electrode becomes suppressed. In this way, activity in neural circuits of the human brain can be stimulated or inhibited by this non-invasive technique. This new study used tDCS to modulate a neural circuit that has been implicated in impulse control while test subjects were in an fMRI machine so that changes in neural activity in these brain circuits could be monitored while they were provoked to anger. 

The limbic system is a central hub of threat detection and anger, but the prefrontal cortex, situated in the forehead region, can suppress anger and aggression through descending connections that modulate the limbic system. Temper tantrums are common in juveniles because these connections from the prefrontal cortex are not fully developed until after adolescence. This is the biological underpinning of why juveniles are not held criminally responsible to the same extent as adults—they do not have the circuitry an adult has to control impulsive anger. These circuits can be disrupted through life experience, genetics, drugs, or disease, and fail to perform their normal function to squelch violent impulses, leading to bursts of anger, assault, and violent crime.   

A particular region of the prefrontal cortex (the vmPFC) becomes engaged during anger and aggression, as can be seen by using fMRI; tDCS has been used to explore and manipulate neural circuitry in many types of neurobiological and psychological experiments, but whether the stimulus acts as a placebo or operates indirectly by providing a subtle sensation that acts as a cue has raised considerable controversy. In this new study, the researchers were able to show that tDCS effectively increased neural activity in the vmPFC by using functional brain imaging, and when this circuitry was activated by the applied voltage, anger was suppressed. The subjects in the study participated in a game in which a monetary payout was distributed fairly or unfairly. Naturally, being “cheated” provoked anger in the test subjects, which was rated by the participants on a scale of 1 to 10. When participants in the game felt cheated, their level of anger was reduced when tDCS was applied to activate the circuits from the vmPFC that inhibit the amygdala in the limbic system. Sham stimulation designed to produce similar sensations on the skin but not manipulate activity in neural circuits served as a control. 

The purpose of the study is to identify and understand the neurobiological circuitry of anger and aggression, but the authors state that the findings have potential use clinically. Anger and aggression provoked by interpersonal provocations are common in numerous psychiatric disorders and medical conditions, and there is a need for better treatments than the currently available drugs, counseling, and the last resort of incarceration. The authors state that their findings suggest that tDCS may provide “a non-invasive adjuvant to improve anger coping capabilities in individuals with pathological manifestations of anger, and perhaps also for therapeutic inoculation for populations at risk of developing such pathology.” In other words, acting as a pacemaker for the brain, tDCS may hold the promise of an intervention to prevent the type of ticking time-bomb and the senseless tragedy that everyone involved with Bellamy saw coming and tried, but failed, to prevent.