Brains at work
MRI scanner at Penn State Hershey Medical CenterCredit James Collins
To Eslinger such clues were tantalizing, but there was only so much to be inferred from clinical symptoms. "It's like something going out on your car, and just by looking at that part trying to figure out how the rest of the car works," he says, shrugging. Now, however, using functional magnetic resonance imaging, or fMRI, he can literally see the brain at work.
Like its now well-established cousin structural MRI, fMRI takes advantage of the inherently magnetic property of water molecules within the brain. The high field MRI machine first exposes the brain to a powerful magnetic field that causes the hydrogen protons in those water molecules to line up. Then it uses electromagnetic waves to knock the protons out of alignment. Finally, it stops the waves and measures the time it takes for the protons to relax back into line. Data collected about the relaxation time at each brain location (or pixel) are then translated into a high-resolution image of living neural tissue.
"When specific brain areas become more active, they demand more glucose and oxygen, so the blood flow increases," Eslinger explains. "We can usually see a three to five percent change over a period of just a few seconds. We can look at the anatomic distribution of the activity, and the volume of it. We can determine if change happens very quickly or it's something that takes time to develop."
Eslinger had already used fMRI in a variety of projects at Hershey's Center for Nuclear Magnetic Resonance Research in collaboration with MRI physicist Qing Yang (see sidebar) when he was contacted in 2000 by Jorge Moll and Ricardo Oliveira-Souza, two Brazilian neuroscientists interested in the neurobiological bases of antisocial behavior. Moll and Oliveira-Souza had read Eslinger's brain-injury work, in which, as Eslinger now says, "we were beginning to identify that the effects of these rare injuries were real and measurable, that some sociopathies weren't a matter of not trying, or being poorly educated, or growing up in an abusive environment. They had physiological causes, just as a weakness in the arm or a loss of speech did."
Moll and Oliveira-Souza had hopes of impacting public policy on crime and punishment in Brazil by better understanding the roots of violence and aggression, Eslinger remembers. "They were specifically interested in what we call 'snakes in suits,' the well-cultured sociopaths who exist in all societies. If you do structural scans of their brains, they look the same as anyone else. If you test them on moral inventories, they can score just as well, if not even better. They know the rules, they know what's right and wrong, but the difference is that such knowledge doesn't guide their behavior.
"How is it that these people can be habitual killers, rapists, swindlers, and all sorts of things, and yet look so normal? Is there something else going on in the brain?"
The emotional response
At the Hospital Barra D'Or in Rio de Janeiro, Eslinger and his new collaborators tested a group of normal adults by asking them to view images of emotionally charged scenes with and without "moral" content while lying inside an fMRI magnet. Pictures of physical assaults, war carnage, and abandoned children were included in the moral category; the non-moral images depicted body lesions and dangerous animals.
As the researchers predicted, certain brain regions (the amygdala, thalamus, and upper midbrain) were consistently activated by both types of emotional stimulus. But some areas, including the orbital prefrontal cortex (OFC), located just above the eye sockets, and the superior temporal sulcus, at the furrow between the frontal and temporal lobes, fired specifically in response to moral content. Moreover, "We found that this activation was very fast," Eslinger reports. "People detected that something was wrong very quickly. It's almost as if the moral content is embedded within the perception. You don't have to stop to think." When they later showed the same pictures to a group of diagnosed sociopaths, he adds, their reactions differed, and these "cortico-limbic circuits" didn't consistently activate.
Paul EslingerCredit James Collins
To Eslinger, these findings suggested that "snakes in suits" may have specific neural deficits that preclude social emotional responses. It also confirmed that the "automatic" processing of moral emotions, mediated in the OFC (the region where Phineas Gage sustained damage), is a separate task from moral reasoning, which is a slower, deliberative process that takes place elsewhere in the brain, where "snakes" have no damage.
Other imaging experiments have tended to support this separation. At Princeton, psychologist Joshua Greene and his colleagues applied fMRI to the trolley problem, a classic ethical dilemma where a subject is asked to imagine him or herself observing an impending catastrophe involving a runaway train. If the observer does nothing, the train will kill five people tied to the track. By pulling a switch, the subject can divert the train, saving the five at the cost of killing a single person tied to the second track.
"If you change the scenario so that the subject has to push that lone person onto the track to save the others," Eslinger notes, "this dramatically switches activation into the emotional parts of the brain, in particular the OFC. The cognitive aspects—weighing of cost vs. benefit—are about the same, but the direct role generates more of an emotional response."
Meanwhile, Moll, Oliveira-Souza, and Eslinger have worked at trying to pinpoint specific moral emotions. Compassion and guilt, they have found, light up differently in the brain. So does disgust, a kind of built-in protection against antisocial behavior which University of Virginia social psychologist Jonathan Haidt calls "the emotion of civilization."
To brain researchers, disgust is interesting because it has "multiple domains," i.e., it can be both a basic emotion and a moral one. Pure disgust, Eslinger explains, is a visceral, primordial response. "It's when you want to eject something because it smells or tastes bad—sour milk or rancid meat." Moral disgust, or indignation, is something more abstract: the reaction to a person whose behavior we judge as wrong. "Yet the impulse triggered is similar," Eslinger says. "Break off contact, withdraw from the offending source."
Moll and Eslinger asked subjects in the magnet to read statements describing disgusting scenarios of both types. (Pure disgust: "A man died after eating a living rat." Indignation: "A newspaper reports a mother is beating her child in a supermarket parking lot.") As expected, the scans elicited showed some distinct differences in brain activity. But they also showed "remarkable" overlap, Eslinger says. "When we presented the more abstract social scenarios eliciting disgust, we found that several of the areas that activated were those also associated with visceral disgust from smell and taste. So part of the comprehension and intensity of the social and cognitive concepts may be built on top of this real primitive reflex."
Bones was right
To Eslinger, these findings, even though preliminary, confirm what he has long suspected: that everyday morality is essentially a gut response. "Our behavior when we're driving a car, when we get back too much change from a cashier—these are accultured behaviors we acquire developmentally, and they become incorporated into our daily routines until we don't even think about them," he says. "Waiting in line instead of cutting in front is not something you weigh the pros and cons of. It's just something you do."
More complicated moral decisions—what we sometimes call moral dilemmas—also involve the emotional circuits in the brain, Eslinger contends, but in this case they work in concert with rational processes. As he, Moll, and Oliveira-Souza write: "This integrative perspective contrasts with the commonly held view that 'rational' cognitive mechanisms control or compete with emotional ones."
Eslinger's interest now is in using fMRI to understand how moral ability takes shape in the developing brain. "We're asking children and teens questions like 'Is it okay to cut in line? To take a candy bar from the store?'," he reports. "What areas of the brain are being activated when they have to make that kind of judgment? That's really completely unknown at this point. And I suspect that it probably shifts quite a bit developmentally.
"A lot of philosophical teaching emphasizes that it's man's reasoning, control of the wild instinctual things, that makes man different from other animals," Eslinger adds at last. "And what we've come around to say is that's probably not true. It's as much emotion that influences our decision-making and capabilities as cognition, and really it's the integration of those two realms of knowledge and experience. The importance of emotional intelligence is increasingly recognized alongside measured IQ.
"Remember Star Trek? Spock's reasoning versus Bones's gut sense of right and wrong? From the Vulcan standpoint, human emotion was a weakness, but I think the series suggested that it's really a human strength, a vital resource that helps us get through life's difficulties and be resilient.
"I think Star Trek got it right." RPS
Paul N. Eslinger, Ph.D., is professor of neurology in the Penn State College of Medicine; peslinger@psu.edu. Qing X. Yang, Ph.D., is associate professor of radiology and neurosurgery at the Center for NMR Research in the department of radiology in the College of Medicine; qyang@psu.edu. The Center provides MRI and fMRI support to investigators at the College of Medicine and at University Park. Visit the Center online.