Neural basis of contagious itch and why some people are more prone to it
- aDepartment of Psychology, University of Hull, Hull HU6 7RX, United Kingdom; and
- bSchool of Psychology,
- cSackler Centre for Consciousness Science,
- dSchool of Informatics and Engineering, and
- eBrighton and Sussex Medical School, University of Sussex, Brighton BN1 9QU, United Kingdom
Edited by Dale Purves, Duke–National University of Singapore Graduate Medical School, Singapore, and approved October 12, 2012 (received for review September 19, 2012)
Watching someone scratch himself can induce feelings of itchiness in the perceiver. This provides a unique opportunity to characterize the neural basis of subjective experiences of itch, independent of changes in peripheral inputs. In this study, we first established that the social contagion of itch is essentially a normative response (experienced by most people), and that the degree of contagion is related to trait differences in neuroticism (i.e., the tendency to experience negative emotions), but not to empathy. Watching video clips of someone scratching (relative to control videos of tapping) activated, as indicated by functional neuroimaging, many of the neural regions linked to the physical perception of itch, including anterior insular, primary somatosensory, and prefrontal (BA44) and premotor cortices. Moreover, activity in the left BA44, BA6, and primary somatosensory cortex was correlated with subjective ratings of itchiness, and the responsivity of the left BA44 reflected individual differences in neuroticism. Our findings highlight the central neural generation of the subjective experience of somatosensory perception in the absence of somatosensory stimulation. We speculate that the habitual activation of this central “itch matrix” may give rise to psychogenic itch disorders.
- ↵1To whom correspondence should be addressed. E-mail: .
Author contributions: H.H., A.K.S., and J.W. designed research; K.W. performed research; H.H. and K.W. analyzed data; and H.H., A.K.S., H.D.C., and J.W. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1216160109/-/DCSupplemental.