Study Reveals Brain Areas Responsible for ‘Contagious Itch’
When some people hear a story about bed bugs or see others scratching for any reason, they immediately start itching. This involuntary “contagious itch” can afflict a wide range of people, but especially atopic dermatitis patients, who remain at particularly high risk.
Previous studies trying to figure out the connection only scratched the surface. But now a study using functional MRI is taking a deeper look.
Researchers assessed 11 people with atopic dermatitis prone to contagious itch and showed them two six-minute videos. When they saw a video of people scratching, the supplemental motor area, left ventral striatum, and right orbitofrontal cortex regions of their brains lit up on imaging. These highlighted areas on fMRI imaging indicate more activity. The fMRI revealed significantly higher brain activity in these areas compared to when participants with atopic dermatitis watched a control video of the same people sitting idle.
In addition, their itching and scratching also significantly increased while watching the video of people scratching, aligning with the imaging findings.
“We initially thought that the premotor cortex will be the major area that is activated,” said Gil Yosipovitch, M.D., Director of the Miami Itch Center and professor of dermatology at the University of Miami Miller School of Medicine. The premotor cortex contains what are called the “mirror neurons” – which are activated when animals or people see others performing an activity, like yawning, and mimic it. However, the investigators did not see greater activity in that region of the brain.
“But we showed the supplemental motor area and ventral striatum is highly activated,” Yosipovitch said. “This is what is unique in the results of this study,” published July 25 in Frontiers in Psychology.
Clinical applications to help people unable to control contagious itching may not be far off. “Indeed, we think that in the near future we can target brain areas that are involved in this phenomena and the urge to scratch, and reduce these sensations,” senior study author Yosipovitch said. “We are planning to do several non-invasive therapies targeting the brain to attenuate the itch perceptions in patients.” His group also plans to conduct studies targeting the brain areas involved in itching and scratching in both animal models and humans.
The research is an example of cross-disciplinary, international collaboration. Yosipovitch worked with MRI expert Hideki Mochizuki, Ph.D., now at the University of Miami Miller School of Medicine, and Christina Schut, Ph.D., a psychologist from Germany who completed her post doctorate with Yosipovitch.
“The UM environment cultivates cross collaborations between disciplines,” Yosipovitch said. “This is extremely important for future projects and funding in an era of limited federal funding, as each group adds their expertise and the studies are of higher quality. This is why I and all my team moved here to UM a year ago and opened the Miami Itch Center.” His team is already collaborating with researchers in neuroscience, brain imaging, and psychology and with investigators at Bascom Palmer Eye Institute.