Central mechanisms of itch

• This review article discusses functional roles of brain regions activated by itch stimuli, in particular the primary and secondary somatosensory cortices, the cingulate cortex, and the insular cortex.
• The central mechanisms of the itch modulation system, contagious itch, and pleasurable sensation evoked by scratching are also discussed.
• The cerebral mechanism of itch partly differs between healthy subjects and chronic itch patients.

Itch is a complex sensory and emotional experience. Functional brain imaging studies have been performed to identify brain regions associated with this complex experience, and these studies reported that several brain regions are activated by itch stimuli. The possible roles of these regions in itch perception and difference in cerebral mechanism between healthy subjects and chronic itch patients are discussed in this review article. Additionally, the central itch modulation system and cerebral mechanisms of contagious itch, pleasurable sensation evoked by scratching have also been investigated in previous brain imaging studies. We also discuss how these studies advance our understanding of these mechanisms.