Study probes affective touch

Thao Do staff illustrator touch scitech
Photo by Thao Do.

According to recent research from the Yale Child Study Center, children develop unique brain mechanisms to help them understand the social importance of touch.

In a collaboration between Yale University and the University of Gothenburg in Sweden, researchers studied brain responses to soft brush strokes on children, adolescents and adults. Whole-brain analyses with fMRI imaging showed that the ipsilateral secondary somatosensory cortex (SII) — a key region of the brain that processes touch — displayed increased activity with greater age. This new understanding of social touch is the first to establish a developmental progression of the neural mechanism and holds promise for application for autism research, said study co-author and professor of psychology Kevin Pelphrey.

“We were interested in how the human brain develops the ability to understand the social importance of touch as opposed to just registering pain,” Pelphrey said. “We were after the actual social meaning of touch.”

Though parental touch has long been known to play an important role in the development of offspring, there has been no significant research published that details the neural development of touch processing in humans.

During the study, test subjects were stroked with a watercolor brush on the palm and forearm to stimulate low-threshold mechanoreceptors, which are activated in humans in response to non-painful touch. While stimulating the skin receptors, the research team took fMRI scans of the different age groups.

The ipsilateral SII region of the brain showed increased activity as the ages of the test subjects increased. In addition to the ipsilateral SII increase, females also exhibited increased neural sensitivity with age in the superior temporal sulcus, a region of the brain responsible for social cognition functions.

The study is the first to reveal noteworthy sex differences in the development of brain processing of affective touch, said Helena Rutherford, a research scientist at the Yale Child Study center who was not involved in the study. The research can potentially answer questions on the puzzle of sex-specific neurodevelopmental disorders, and Rutherford said the publication is a significant contribution to the emerging literature on affective touch. According to the Centers for Disease Control and Prevention, autism spectrum disorders are roughly five times more prevalent among boys than girls.

Children with autism often exhibit a similar neural response to affective and tactile touch, and the neuroimaging results of the study can help in early autism detection, Pelphrey said.

Fred Volkmar, a professor of child psychiatry at the Yale-New Haven Children’s Hospital, said he found the study a sign of progress in understanding human development.

“We have become increasingly able to employ sophisticated methods of study to what seem like, and are, basic aspects of human social development,” Volkmar said. “This study highlights how far we have come, and has important implications for understanding both normal development and early onset disorders like autism.”

The study was published on Feb. 4 in the journal Frontiers of Behavioral Neuroscience.

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