No Pain, No Nerves

FEELING LEFT OUT HURTS:

REVIEW OF AN fMRI STUDY OF SOCIAL EXCLUSION

Eisenberger, N., Lieberman, M., Willams, K. Does rejection hurt: An fMRI study of social exclusion. Science, 10/10/03, Vol. 302 pgs. 290-292

Constantine Fisher

PSY 371 -Neuroscience

Paper # 1

9/17/07

To a child, a "hurt feeling" can be just as bad as a scraped knee. Though these are different types of pain, they can elicit the same cry of discontent. As we grow, our thoughts become more complex and our system of processing statements and emotions becomes more sophisticated. However, the unhappiness felt when one senses that he or she is not being accepted socially remains intact. It may be the case that evolution has not only provided us with an alarm system to avoid physical harm, but also emotional harm as well. Research done by Naomi Eisenberger, Matthew Lieberman, and Kipling Williams suggests that there is a common neural circuitry involved in processing the pain of both the sting of a pointed needle as well as the sting of a pointed remark. Two areas that are known to be keys in the processing of physical pain were of particular interest to the researchers in their study.

The first area, the anterior cingulate cortex (ACC) is known to be activated by pain. Specifically, the ACC is involved in discriminating if a response to a stimulus will cause more pain or alleviate it, which is the autonomic goal. It is possible that, since social connectedness is vital to human life, the ACC is activated when there is something wrong in a social sense. The destruction of the ACC in hamster mothers has been shown to stop maternal behavior in keeping the young close by,1(10) and, similarly, the destruction of the ACC in squirrel monkeys has been shown to stop their separation cries that are usually emitted when they are separated from their group.1(11)

The second area, the right ventral prefrontal cortex (RVPFC), helps dampen the emotional distress caused by pain. Activation of this area has been shown to lessen pain response in rats when they are exposed to a painful stimulus.1(19)

To test the hypothesis that the brain bases of social pain are similar to physical pain, Eisenberger, Lieberman, and Williams utilized functional magnetic resonance imaging (fMRI). By using fMRI, the amount of blood flow in real-time could be seen in different areas of the brain; an area that was being utilized more would command more blood flow and would thus appear a brighter color on an fMRI monitor. Subjects were recruited to play a game of "Cyberball," a virtual ball-tossing game, while inside an fMRI scanner with who they believed were two other players also in fMRI scanners. The other players however, were computer simulations designed to exclude the participant after a designated number of throws. The researchers tested both explicit social exclusion (ESE), in which the subjects were purposefully ignored, and implicit social exclusion (ISE), in which the subject was told that, due to extenuating circumstances such as a failure to link the system to the Cyberball game, he or she could not be involved in the activity although he or she could watch what was happening. After the conclusion of the game, the subject was given a survey to determine his or her distress levels at different points in during ESE. Under this setup, the independent variables were ISE and ESE, whereas the dependent variables were ACC and RVPFC activity.

The results of the experiment supported the hypothesis. Group analysis of the fMRI data indicated that ACC activity was elevated during ESE. Self-reported distress during ACC activity was shown to be significant (significant meaning that the P value

was less than 0.05). This suggests that ACC activation during ESE was associated with emotional distress in a similar fashion that showed ACC activity elevation during physical pain.1(7,8) The anterior insula was also shown to active during ESE, but it did not

significantly correspond to distress levels (P > 0.5). The RVPFC was also shown to be more active during ESE. RVPFC activity, however, was shown to be negatively correlated with self-reported distress levels during ESE relative to inclusion (P <