I'm starting a new feature. I debated starting my own blog, but I'm no Pharyngula. Heck, I'm not even DarkSyde.
Psychiatry Sunday (or Monday, or Thursday, or whenever I can write a column) will be dedicated to relatively new research that lends insight into the functioning of the human mind and its dysfunctions. It is not overtly political, but it is written by a Liberal Libertarian who tries to balance the social contract with his own independence ... so empathy and the building of empathy is inherently assumed to be a positive human attribute.
In that spirit, I decided to start with an article that is almost one year old. It's a fairly good starting point to introduce some new concepts, it doesn't require image posting, and it deals with a phrase from one of our recent Democratic Presidents: "I feel your pain." What does it mean to feel another's pain? What are the implications? It's also a fairly uniquely human skill, although the trait arguably exists in more rudimentary form in rodents, canines, and other primates.
Chris Frith is a neuroscientist at the University College of London's Neurology Department. He deals with how the brain picks up on the intentions and feelings of others, and how it keeps them discrete from one's own thoughts, feelings and planned actions. He's one of the pioneers in a new area of Neuropsychiatry, which we'll call "Mirror Neuron Neuroscience." You may have read about mirror neurons in the New York Times or some other Popular Science publication, and we'll discuss them at greater length in another diary. Suffice it to say that this area of study deals with brain circuitry that is fairly refined in primates, and seems to be central to imitative learning. It links "monkey see" and "monkey do." In humans (and other apes to some extent), cerebral cortical regions involved with mirror neuron circuitry have undergone the greatest degree of growth, and are now thought to aid in what cognitive psychologists call "theory of mind." Theory of Mind is how I can guess at what you're thinking, based on words, deeds, and body language.
Frith has mainly been studying theory of mind and the self-other boundary through functional magnetic resonance imaging (fMRI). Although fMRI is slangily referred to as "brain activity imaging," what it actually does is superimpose changes in blood oxygenation over short periods of time upon a structural map of the cerebral cortex. How fMRI picks up changes in blood oxygenation is better explained by the physical chemists at dKos, but the important thing to know is that scientists have good reason to believe that changes in brain region activity correlate well to blood oxygenation changes. Why? Well, when neurons get active, they deplete the local blood pools of oxygen and nutrients. In turn, the cerebral vasculature is highly responsive to these changes and dilates to bring in more blood. Thus, there is a discrete drop in oxygenation when brain regions get highly active, which is limited in time. By staggering the periods of time when the magnet in the fMRI is assessing blood oxygenation to different parts of an experimental task, a picture of brain activation throughout a task or application of a stimulus can be assembled.
Last February, Frith and his colleagues published their findings on the process behind sensing pain in another person (http://www.sciencemag.org.ezproxy.med.nyu.edu/...). It is part of the investigation into the empathic elements of theory of mind.
Pain, from static electric shock to pinprick to stab wound, is sensed through processing in discrete regions of the cerebral cortex. Some other time, we'll talk about how the signal gets from the periphery (where you are hurt) to the brain, but let's just focus on the cerebral cortex right now. There is an area of the brain, about halfway between your face and the back of your head, called the primary somatosensory cortex, or S-I for short. This is where tactile input first comes through the processing stream from the periphery into the cerebrum. In many textbooks, it's drawn as a little person, because different regions of S-I correspond to different regions of the body. However, it actually looks more like a diagram of cuts of beef at the butcher's counter, a hamhock shaped piece of cortex divvied up into zones corresponding to hands, fingers, face, trunk, etc. Each hemisphere of the cerebral cortex has an S-I, which mainly (or entirely, depending on which scientist you're talking to) process information from the OTHER side of the body. So, the left hemisphere S-I processes and localizes tactile stimuli from the right side of the body. This schema is repeated in several areas of the cerebral cortex (left visual cortex processes stimuli from right half of space, left motor cortex helps to program actions on the right side of the body).
In addition to S-I, painful stimuli strongly excite neurons in secondary somatosensory cortex (S-II). Each hemisphere has an S-II, located just slightly "lower" (ventral) on the cortical surface than S-I. S-II neurons also mainly deal with contralateral stimuli from the other half of the body, but more of them can encode ipsilateral (from the same side) stimuli (and few neuroscientists disagree on this point). S-II is believed to assist the conscious discrimination of tactile stimuli, like textures and edges, and refine the localization on the body surface (in tandem with S-I). Pain also strongly activates the insula, a piece of cortex tucked in the crevice between the "thumb" (temporal lobe) and "mitt" (parietal lobe) of each hemisphere. The insula receives multiple forms of sensory stimuli, and is thought to lend the "affective" component to experiences. Noxious stimuli (like pinpricks) and pleasurable stimuli (like the sight of puppies) both strongly activate the insula. How the insula and the rest of the brain sort out disgust from pleasure is still not entirely understood (but the answer probably has something to do with the brain chemistry/circuitry of sado-masochists).
Pain also activates: the anterior cingulate cortex, a region that associates rewards/punishments with actions/reactions and is key to learning; the supplementary motor area, another region central to higher-order planning and reactions; subcortical sensory (thalamus) and motor (cerebellum and thalamus) parts of the central nervous system. Pain is localized (thalamus, S-I and S-II), associated with negative outcome (insula and anterior cingulate), and plans are made to get the body away from the source of the pain (anterior cingulate, supplementary motor area and cerebellum).
So, thought Frith, what happens when we image subjects as their significant other is subjected to a small electric shock? This study, by the way, was done with full consent of both members of the 16 couples. The electric stimulus was noxious but not harmful (analogous to unpleasant amount of static electricity). And no, the girlfriend didn't get to shock her boyfriend.
The woman was imaged while watching her right hand and her partner's right hand through a series of mirrors. Cues indicated whether she would get a stimulus or her partner would. Prior to scanning, the woman was asked to rate the unpleasantness of several electric stimuli. This way, the experimenters knew her threshhold for unpleasant experience. A series of stimuli was given to the woman being scanned or to her partner, after which the woman was asked to rate the relative unpleasantness of stimuli given to her or her partner. These correlated well with the pre-scan ratings, whether they were given to her or to her partner. This was the first indication that empathic pain was analogous to directly received pain, even before the brain data were looked at.
Whether pain was directly received or applied to the partner, the insula and the anterior cingulate "lit up." In other words, the brain registered a noxious stimulus and associated it with the task at hand. There was even cerebellar and brainstem activity associated with both conditions, suggesting that there may have been preparation to withdraw the hand (or pull away the partner's hand?) even when the pain was not directly received.
When pain was directly received, S-I and S-II were more strongly activated, consistent with the localization of pain upon the body and association with the self. There were partially, but not completely, overlapping regions of the insula and anterior cingulate cortices that were also activated by directly received pain. The insula and the cingulate cortex are thought, based on experiments in humans and monkeys, to contain "mirror neurons" and "self-only neurons." Frith seems to have dissected out "mirror" and "self" patterns of activation in the insula and cingulate, that register empathic and received pain respectively.
When pain was witnessed, the higher order visual areas of the cortex were more strongly activated. So, pain can be received, processed and understood through tactile cortices, and registered as a noxious stimulus OR it can be witnessed in another, processed and understood through visual cortices, and STILL registered as a noxious stimulus.
Finally, Frith compared the relative activation of the cortex to empathic pain with scores that each of the subjects had on traditional psychological questionaires meant to assess empathy. Did the imaging of empathy square with the psychological assessment of empathy?
Absolutely. Not only did high scorers on the empathy scales have greater activation in the insula and anterior cingulate cortices, but the proportionally greater activation was localized to the regions of the insula and the cingulate that were specific to the empathic condition and not the received pain condition. Their mirror neurons in the insula and cingulate appeared to be more responsive, further suggesting that this was the biological substrate for their empathic ability.
So, what are the implications? Well, as I'll continue to discuss in other diaries, although both we and the monkeys have mirror neurons (and probably rats and dogs do too), we already have good data that monkeys do not have such nuanced mirror neuron abilities. Their theory of mind sucks ... they are really poor at judging your intent beyond very crude and broad categories (trust me when I say you have to be very careful about your body language with the little buggers).
Humans, though, use this system that probably arose for imitative learning (mainly actions of the hands) to assess the state of mind of other humans. We interpret actions and even RE-actions to stimuli and glean streams of thoughts. Forget ESP and Jedi Mind Tricks ... humans already have an ability to read minds ... we just don't think of it as anything magical. But it is. As Richard Leakey is fond of saying, a two legged animal like a human must find a way to cooperate in a band or he/she is screwed when he breaks just one leg. To gain skilled hands, we had to free them up and walk on two legs. To keep the hands free and to keep us alive in that state, we had to band together. To do so, and remain individuals, evolutionary pressure favored the growth of the visual imitation pathways to become refined for intention assessment and empathic judgement. We are drawn to each other for our own good.
Of course, this is not infinite. We band into tribes. Our frontal lobes, as we deliberate and decide who is on "our side," influence the mirror neuron circuits to be more or less responsive to the events that befall particular individuals or groups of others. And just as some of us are better pitchers or better mathematicians, some of us are innately better empaths. I like to think that these people tend to seek out certain professions, ones that we are discovering hone the theory of mind skills as part of their training pathway. I'll let you figure out what professions those might be.
It also gives us an important insight into the nature of modern warfare. Why is it easier for humans to press buttons and pull switches to kill hundreds or thousands? Because these technologies deprive the central nervous system of the key visual input needed to activate the mirror neuron system robustly. Yes, the psychology experiments of the 1950s and 1960s also showed the importance of authority figures in bureaucratic genocide and modern warfare. But the inability to see the direct effects of actions on individuals probably plays a huge role as well. If you just perform one small part of the horrible action, or you press a fire button on a missile that flies away ... that takes away a bit of the pathway to empathy right there ... and if you are indoctrinated to believe that the "other" shouldn't factor into your empathic considerations ... that takes another piece.
How are we affected, citizens in a virtually total media blackout of the consequences of our wars? Yes, sometimes we see a bombed house and screaming children, once in a while. But we don't see our soldiers running in and shooting people. We don't see our drones bombing the villages, and even when we do, it looks like a video game or a science fiction film ... the human element has been completely removed ... and our overgrown monkey brains cannot register the vitally important sense of empathy to rein us back in. Well, in the end, I guess that's the kind of politics I'll inject ... until next time, here's hoping you gleaned some of my intentions.
BTW, if anyone can tell me how to paste images into a diary, I'd appreciate it. I have been looking for the "how to" guide to give links and post images, and I can't find it.