A heterosexual man may experience a caress by a woman as divine and the same caress by a man as frightening. How does that work in the brain?
Researcher couple Valeria Gazzola and Christian Keysers, both at the Academy’s Netherlands Institute for Neuroscience (NIN) and the University Medical Centre Groningen (UMCG), published an article in the leading science journal Proceedings of the National Academy of Sciences on that topic this week. The article sheds new light on the old idea that there are regions of the brain that only respond to touch objectively and other regions that respond to it subjectively.
In their study, Keysers and Gazzola observed brain activity in male subjects who had their legs stroked sensually under two different conditions. In the first condition, the subjects watched a film of an attractive woman bending down to caress them. In the second, they watched a film of a man doing the same. The subjects’ legs were stroked sensually as they watched the films, and they thought that either the man or the woman was caressing them. They did not know that it was in fact the woman caressing them under both conditions. As anticipated, they found being caressed by the woman pleasurable and being caressed by the man unpleasant. But what happened in their brains?
“According to traditional theories about the way the brain functions, there is one region of the brain that simply registers the physical properties of a touch on the skin. That region is known as the somatosensory cortex. But there are other brain regions thought to determine how pleasurable a touch is, depending on what we see and feel for the person who is touching us," says Valeria Gazzola.
The researchers discovered that, although the subjects were caressed in the same way each time, their “objective” somatosensory cortex responded much more strongly to the “female” touch than it did to the “male” touch. It turns out that observation is not objective but is heavily influenced by the feelings evoked by what we observe. “We observe the world through the prism of our emotions,” according to Christian Keysers.
Valeria Gazzola is the senior scientist at the NIN and the UMCG and is the lead author of the article. Christian Keysers is the head of the NIN’s Social Brain Lab, professor for the Social Brain at the UMCG, and the senior author of the article. Other researchers who contributed to the article are Fulvia Castelli (University College London), Joset Etzel (University of Groningen), Michael Spezio (Scripps College, Claremont) and Ralph Adolphs (Caltech Brain Imaging Center, where the research was carried out).
The study was funded by the Gordon and Betty Moore Foundation, NWO, a Scripps College Faculty Research Grant and a Marie Curie Excellence Grant.