Placebo’s Double Whammy

Sham treatments can both reduce pain and increase pleasure, and do so affecting similar circuitry in the brain.

By | October 14, 2013

WIKIMEDIA, ROBIN_24Expectations give placebos their power, allowing them to dramatically alter our experience of a stimulus. Researchers demonstrate in Proceedings of the National Academy of Sciences today (October 14) that not only can placebos tamp down feelings of pain, they can also ramp up pleasurable sensations. It all depends on where a person starts. If she is expecting an improvement in pain, her sensory processing decreases. If, on the other hand, she anticipates a heightened sense of pleasure, then the sensory processing is magnified.

The researchers, led by Dan-Mikael Ellingsen at Gothenburg University in Sweden, offered a nasal spray placebo (supposedly containing oxytocin) or nothing at all to 30 study participants. On one day, the participants received gentle strokes on the left arm; on another day, a painful heat stimulus. In the pain scenario, the nasal spray was tied to a decrease in pain sensation, and in the pleasure scenario, it was associated with an increase in pleasure, compared to the times when the person was given no spray.

Using functional MRI, the researchers found increases in activity in the posterior insula and primary and secondary somatosensory areas—regions involved in sensory processing—during the pleasurable arm stroke placebo treatments. They also found decreases in these areas during the painful heat placebo sessions. These results suggest that a placebo can enhance good feelings by increasing sensory processing and squelch pain by decreasing sensory processing.

Interestingly, they also found that parts of the brain involved in reward and emotion, a network they called “emotion appraisal circuitry,” were activated in both the painful and pleasant situations. The researchers interpret this activation in both scenarios as having opposing regulatory effects on sensory processing. “Overall, our results suggest that emotion appraisal circuitry is recruited by expectations of a benefit, whether it is pain relief or enhanced pleasantness of a positive stimulus, and modulates sensory processing accordingly to meet these predictions.”

The research team says that focusing on both the pain-reducing abilities of placebos and the pleasure-enhancing abilities are important in clinical studies.

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Avatar of: PRice


Posts: 9

February 22, 2015

It was hilarious how the researchers used studies of oxytocin to create expectations in the subjects. “To induce expectation of intranasal oxytocin’s beneficial effects on painful and pleasant touch experience, participants viewed a 6-min locally developed video documentary about oxytocin’s putative prosocial effects such as involvement in bonding, love, grooming, affective touch, and healing. As all of the material was based on published research, there was no deception. The video concluded that a nasal spray of oxytocin might enhance the pleasantness of: (i) stroking and (ii) warm touch, and (iii) reduce the unpleasantness of pain.”

More interesting items:

    Only the placebo effects for the warm and pain-reducing touches were statistically significant, not the stroking touch;
    The a priori brain areas monitored in the “sensory circuitry” included the thalamus and were all in the right brain hemisphere;
    The a priori brain areas monitored in the “emotional appraisal circuitry” included the amygdala.

One way the researchers summarized the study was: “Pain reduction dampened sensory processing in the brain, whereas increased touch pleasantness increased sensory processing.”

I would summarize this finding as a demonstration of how the thalamus part of the feeling brain actively controls and gates information reaching the thinking brain.

There was a terminology problem in the study evidenced by statements such as: “We induced placebo improvement of both negative and positive feelings (painful and pleasant touch)..” Touch is a sensation, not a feeling. This placebo study was all about creating expectations of sensations in the subjects’ thinking brains.

I would further note that including parts of the feeling brain such as the amygdala in the “emotional appraisal circuitry” does not mean that the researchers studied feelings or emotions. We know from other research “..neither amygdala activity nor amygdala-controlled responses are telltale signatures of fearful feelings..”

This research casts additional light on a recent problematic research on human happiness study. I’d characterize that study as the researchers becoming fooled by a positive placebo effect!

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