WASHINGTON — Two new brain-imaging studies describing the origins of empathy and how placebos work provide insights into the nature of pain, the mind-body connection and what it means to be human.
Whether we’re feeling empathy when a loved one endures pain, or enjoying pain relief thanks to a placebo, pain-sensitive regions of our brains are at work — either creating or diminishing the experience of human pain. These findings appear in two papers published in Friday's issue of the journal Science, published by AAAS, the nonprofit science society.
Empathy is the human ability to feel what others feel. Humans use empathy to better navigate the social environment and answer questions such as: Is this person going to attack me? Faint? Run away? Cry?
“For humans, the more accurately you can predict the actions and needs of others, the better off you are,” said author Tania Singer from the Wellcome Department of Imaging Neuroscience at University College London.
Moreover, the ability to “tune in” and empathize with others is a prerequisite for understanding, attachment, bonding and love — all of which are important for our survival, according to Singer.
Empathy is pain … sort of
In their studies on human volunteers, Singer and her colleagues found that feeling empathy activates some, but not all, of the pain-processing regions of the brain.
In a classical example of pain, such as grabbing a hot spoon handle, the burning pain shoots into temperature receptors on your skin, through nerves, up your spine and into your brain. Some regions of your brain process information such as where the pain comes from and how hot the spoon really was. Other regions of the brain process how unpleasant you felt the pain to be. Thus, how much the burn hurts and how bothersome this pain is differs for each situation and depends, among other things, on what else is going on in your head and the environment.
Interactive: Take a tour of the brain If you are involved in a serious car accident, your survival system is so busy that you hardly feel any pain even though you are severely injured. If, however, you’ve been exposed to someone with chicken pox, the slightest sensation on your skin may feel like the itching pain you are expecting.
The researchers found that empathy activates the same regions of the brain that process these context-dependent aspects of pain, including the anterior insula and anterior cingulate. Knowing your loved one is in pain automatically activates the subjective pain-processing regions of your brain, which leads to empathy. But the areas involved in processing the exact location of the pain in your body as well as the objective intensity of the pain are involved only when you experience pain in yourself.
The researchers studied how this all played out by using a brain-scanning technique called functional magnetic resonance imaging, or fMRI. In the experiments, women who reported the strongest feelings of empathy showed the greatest activity in the context-dependent pain regions as their loved ones endured simulated bee stings. Even when the women didn’t see their partners’ pained faces, their brains reacted.
These findings suggest that humans are hard-wired to empathize. Singer speculated that you are probably better able to empathize with someone when you have experienced emotions and situations similar to those they are faced with. She also suggested we may be able to temper these automatic empathic reactions.
Among many directions for future research, Singer wants to see if liking or disliking someone changes your empathic response to their troubles.
A placebo's active ingredient
When the focus is your own pain, substances with no pharmaceutical value sometimes provide relief. The “active ingredient” in placebo treatments is your brain, according to the second study in Science.
“The experience of pain depends not only on sensory signals coming in, but on your emotional state and how you interpret those signals. Placebos could affect multiple aspects of the experience,” said study author Tor Wager, who recently moved from the University of Michigan-Ann Arbor to Columbia University.
Study participants who reported the greatest placebo-induced decreases in pain showed significantly decreased brain activity in certain pain-sensitive brain regions. Less brain activity in these areas seems to mean less pain.
Activity in some pain-sensitive regions did not drop when placebos relieved pain. This result strengthens the idea that placebos do not block the body’s sensory features that transmit pain from the skin to the brain. Instead, the brain modulates its interpretation of those signals.
When people who responded to placebos anticipated pain, there was a sharp rise in activation of a region of the brain linked to cognitive control, the prefrontal cortex.
In their study, the authors suggest that this brain activity is related to belief in the placebo, and they speculate that it may trigger the release of natural pain-relieving chemicals related to opium, called opioids.
“These findings acknowledge that pain is a psychologically constructed experience,” the authors write. The pain we feel seems to be a product of the sensory information we encounter and the unique ways in which we processes these sensations.
The scientists’ results challenge claims that placebo success stories reflect nothing but biased responses from study participants who somehow feel obligated to report benefits from placebo treatments.
In the future, Wager and his colleagues at Columbia, Michigan and Princeton -- including Edward Smith, Ken Casey, and Jonathan Cohen -- hope to learn just how far the effects of placebos reach inside your body.
“Can placebos, for example, improve immune responses or decrease signs of stress in the body?” Wager asked.
© 2004 American Association for the Advancement of Science