tudying live human brains is tricky. Scientists would love to watch individual neurons communicating with each other in real-time so they could learn to decipher the electrical and chemical language of the brain. They’d love to peer directly into activated brain cells and witness their inner workings on a molecular level. They’d love to see how groups of these cells work in tandem in different regions of the brain. But these kinds of observations cannot be made very easily because of the one major obstacle standing in the way. The skull. Neuroscientists are peeping toms standing outside a house where the windows are shuttered.
They can hook electrodes into the brains of non-human primates. And they occasionally get glimpses inside malfunctioning human brains. For example, when brain surgery is conducted on patients suffering from severe epilepsy, researchers may be afforded an opportunity to look under the hood. But the tool that has proven most useful in studying the brain is functional magnetic resonance imaging, or fMRI.
You might be familiar with the MRI machine. It looks like it belongs in the sick bay on a space ship in a science fiction movie. It’s shaped like a big donut, and the patient lies on a platform that slides head-first into the donut.
The blood that flows through our arteries is oxygen-rich. The oxygen is carried within red blood cells by a molecule called hemoglobin. The oxygen is fed to our various cells, which use it to create energy. The deoxygenated blood then flows through our veins back to our hearts. It turns out this deoxygenated blood is more magnetic than oxygenated blood. And so an MRI machine can create images of blood flow in the brain, and thereby create maps of neural activity.
Our science is not yet advanced enough to determine exactly how empathy works. But thanks to fMRI studies, we’re at least able to determine which regions of the brain are activated when humans experience empathy, and this has led to a few surprises.
In one fMRI study, photos of human limbs in painful-looking positions were shown to subjects while their brains were scanned. The researchers discovered that “the anterior cingulate and anterior insula cortices, regions often reported as being part of the pain affective system, are recruited when watching someone else’s pain.”
When you see someone else in pain, the pain centers in your own brain are activated.
In another study, researchers noted that “watching the movie scene in which a tarantula crawls on James Bond’s chest can make us literally shiver—as if the spider crawled on our own chest.” They asked, “What neural mechanisms are responsible for this ‘tactile empathy’?” Their subjects watched videos of scenes like the tarantula one while their brains were scanned in an fMRI machine. The study revealed a “systematic tendency of our brain to transform the visual stimulus of touch [witnessed in others] into an activation of brain areas involved in the processing of our own experience of touch.”
When you see someone else being touched, the touch centers in your own brain are activated.
Another fMRI study examined the involvement of the anterior insula and adjacent frontal operculum “in the processing of other people’s gustatory [relating to taste] emotions.” Participants were shown photos of faces reacting to tastes. The facial expressions were disgusted, pleased, or neutral. The participants were themselves then exposed to disgusting, pleasing, and neutral tastes.
When you see someone reacting emotionally to tastes, the centers in your own brain that process tastes are activated.
All of this just goes to show that, in the language of the neuroscientists, “common neural substrates are involved in representing one’s own and others’ affective states”,  which indicates that the brain automatically maps “the bodily feelings of others onto the internal bodily states of the observer.” How the brain accomplishes this may involve special brain cells calls mirror neurons, which fire both while performing an action and while observing someone else performing an action. In addition to empathy, these special neurons may account for other important mental functions, like learning new skills through imitation.
In any case, there is overwhelming evidence that we are wired to empathize. Empathy is an automatic mechanism that we employ constantly and unconsciously. It is integral to how we process the behavior we witness from others.
-  It should be noted that fMRI detects neural activity indirectly. It actually maps vascular activity – the pumping of blood. The blood vessels in fMRI images might be a few millimeters away from the activated neurons. And there is a timing difference of up to a few seconds between when neurons fire and when deoxygenated blood appears in nearby blood vessels. Researchers take this timing difference into consideration when designing their fMRI experiments. ↩
-  Jackson, P.L., Meltzoff, A.N., & Decety, J. (2005). How do we perceive the pain of others: A window into the neural processes involved in empathy. NeuroImage, 24, 771-779. http://ilabs.washington.edu/meltzoff/pdf/05JacksonMeltzoff_NeurIm.pdf. A similar study with children as young as seven revealed the same process happening in their brains: Brain Scans Show Children Naturally Prone to Empathy Newswise, retrieved on July 13, 2008. http://newswise.com/articles/view/542456/ ↩
-  Keysers, C. et al. (2004). A touching sight: SII/PV activation during the observation and experience of touch, Neuron, 42:335-46. http://www.socialbehavior.uzh.ch/teaching/semsocialneurosciencews07/touchingsight.pdf ↩
-  ”Empathy for positive and negative emotions in the gustatory cortex”, Mbemba Jabbia, Marte Swarta, Christian Keysersa, NeuroImage Volume 34, Issue 4, 15 February 2007, Pages 1744–1753, See http://www.sciencedirect.com/science/article/pii/S1053811906010780 ↩
-  “Viewing facial expressions of pain engages cortical areas involved in the direct experience of pain”, Matthew Botvinicka, Amishi P. Jhab, Lauren M. Bylsmaa, Sara A. Fabianb, Patricia E. Solomond, Kenneth M. Prkachine, NeuroImage, Volume 25, Issue 1, March 2005, Pages 312–319, http://www.sciencedirect.com/science/article/pii/S1053811904007335 ↩