A recent study published in the Journal of Investigative Dermatology has linked scratching to activity in various regions of the brain. According to Gil Yosipovitch, M.D., and research colleagues, certain areas of the brain increase in activity as a result of scratching while others decrease. Dr. Yosipovitch commented regarding the findings saying, “We know scratching is pleasurable, but we haven’t known why.”
The study focused on a group of 13 volunteers scratched by a brush on their legs in thirty-second intervals, with thirty seconds of rest between, for a total of five minutes. MRI scanning commenced one minute before the stimuli in order to measure brain activities. The following is an excerpt of an article from Medpage Today that reviews the findings of the scans:
Dr. Yosipovitch and colleagues found that the scratching induced deactivation of the perigenual anterior cortex and in the dorsal and ventral posterior cingulate cortex, bilaterally in all cases. Peak Z scores ranged from 2.31 for the right ventral posterior cingulate cortex to 4.05 for the left dorsal posterior cingulate cortex.
When participants reported the most intense sensation from scratching, the level of deactivation in the anterior cingulate cortex was highest.
Earlier studies have connected the anterior cingulate cortex to emotional and cognitive processing, including reactions to unpleasant sensory stimuli, Dr. Yosipovitch and colleagues said.
Deactivation of this region could be one mechanism by which scratching alleviates itch.
Said Dr. Yosipovitch, “It’s possible that scratching may suppress the emotional components of itch and bring about its relief.”