长期以来人们都知道抓挠会使得患慢性瘙痒的患者感到异常舒服，而如今来自塔夫茨大学医学院的研究人员就在研究中阐明了为何抓挠会让患者获得快感，相关研究刊登于国家杂志Journal of Investigative Dermatology上。

　　利用先进的功能性磁共振成像技术，研究者们对10名慢性瘙痒患者及10名健康个体进行研究，当这些个体早抓挠时研究者观察分析了参与者的大脑活性，结果发现当瘙痒患者抓挠时其大脑中涉及运动控制及奖励过程的区域处于异常活性的状态，而这种活性过度的表现或可帮助解释为何慢性瘙痒患者会频繁抓挠患处。

　　研究者Hideki Mochizuki说道，慢性瘙痒是一种皮肤疾病，比如异位性湿疹和银屑病等，尽管抓挠会在第一时间让患者感觉非常舒服或症状得到极大缓解，但不断的抓挠会引发发痒强度的增加，即出现越抓挠越痒的表现，同时也会使得患者出现疼痛和永久性的皮肤损伤，因此揭示患者大脑的活性或可帮助理解机体如何诱发病理性的抓挠行为。

　　此前研究中，研究者调查了个体抓挠的大脑机制，而本文研究首次调查了慢性瘙痒患者在抓挠期间大脑的活性表现；文章中研究者利用一种攀缘植物来诱导慢性瘙痒患者出现瘙痒症状，同时研究者也对未患慢性瘙痒的参与者进行了研究，随后当患者在抓挠时研究者利用功能性磁共振成像技术对参与者的大脑进行成像，结果发现在慢性瘙痒患者的辅助运动区、运动前区皮质及初级运动皮层的大脑活性会明显升高，而这些区域和机体运动控制和运动直接相关。

　　最后研究者表示，本文研究或可帮助阐明引发慢性瘙痒患者疾病表现的原因，而阐明患者大脑活性的变化或可帮助解释患者的抓挠反应，对于后期开发特殊的疗法来有效治疗患者的慢性瘙痒或提供新的研究思路和线索。

　　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.