長期以來人們都知道抓撓會使得患慢性瘙癢的患者感到異常舒服，而如今來自塔夫茨大學醫學院的研究人員就在研究中闡明了為何抓撓會讓患者獲得快感，相關研究刊登於國家雜誌Journal of Investigative Dermatology上。

　　利用先進的功能性磁共振成像技術，研究者們對10名慢性瘙癢患者及10名健康個體進行研究，當這些個體早抓撓時研究者觀察分析了參與者的大腦活性，結果發現當瘙癢患者抓撓時其大腦中涉及運動控製及獎勵過程的區域處於異常活性的狀態，而這種活性過度的表現或可幫助解釋為何慢性瘙癢患者會頻繁抓撓患處。

　　研究者Hideki Mochizuki說道，慢性瘙癢是一種皮膚疾病，比如異位性濕疹和銀屑病等，盡管抓撓會在第一時間讓患者感覺非常舒服或症狀得到極大緩解，但不斷的抓撓會引發發癢強度的增加，即出現越抓撓越癢的表現，同時也會使得患者出現疼痛和永久性的皮膚損傷，因此揭示患者大腦的活性或可幫助理解機體如何誘發病理性的抓撓行為。

　　此前研究中，研究者調查了個體抓撓的大腦機製，而本文研究首次調查了慢性瘙癢患者在抓撓期間大腦的活性表現；文章中研究者利用一種攀緣植物來誘導慢性瘙癢患者出現瘙癢症狀，同時研究者也對未患慢性瘙癢的參與者進行了研究，隨後當患者在抓撓時研究者利用功能性磁共振成像技術對參與者的大腦進行成像，結果發現在慢性瘙癢患者的輔助運動區、運動前區皮質及初級運動皮層的大腦活性會明顯升高，而這些區域和機體運動控製和運動直接相關。

　　最後研究者表示，本文研究或可幫助闡明引發慢性瘙癢患者疾病表現的原因，而闡明患者大腦活性的變化或可幫助解釋患者的抓撓反應，對於後期開發特殊的療法來有效治療患者的慢性瘙癢或提供新的研究思路和線索。

　　doi:10.1038/JID.2015.223

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　　Scratching Induces Overactivity in Motor-Related Regions and Reward System in Chronic Itch Patients

　　Hideki Mochizuki1, Alexandru D P Papoiu2, Leigh A Nattkemper1, Andrew C Lin1, Robert A Kraft3, Robert C Coghill4 and Gil Yosipovitch1

　　Scratching evokes a rewarding and pleasurable sensation in particular in chronic itch patients. To date, no study has investigated the cerebral activity during scratching in chronic itch patients and whether it differs from healthy subjects. Using arterial spin labeling fMRI, we analyzed and compared the cerebral mechanism of self-scratching and its correlation with pleasurability, in 10 patients with chronic itch and 10 healthy controls. Cowhage was applied to the right forearm to induce itch. Scratching significantly attenuated the itch sensation (P<0.001), and evoked an associated pleasurability. Scratching-induced pleasurability significantly activated the reward system in the chronic itch and healthy groups, confirming that this reward system plays a crucial role in scratching-induced pleasurability. A higher activity during scratching in chronic itch patients, versus healthy controls, was noted in brain regions related to motor control and motivation to act, including the supplementary motor area, premotor cortex, primary motor cortex and midcingulate cortex, as well as the caudate nucleus involved in the reward system. This overactivity may be associated with the addictive scratching and/or neural hypersensitization.