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. 2018 Mar 24;17(5):507–516. doi: 10.1007/s12311-018-0933-6

Fig. 3.

Fig. 3

Itch-scratch cycle model in the central nervous system. The sensorimotor regions, such as SI, MI, SMA, and cerebellum, play an important role in processing itching signal. All the above signals may be learned, re-encoded, and memorized in the cerebellum, which may be modified by the reward system. In CSU, the sensorimotor-reward-cerebellum pathway (blue line) may be responsible for projecting itch-scratch signals to the cerebellum through cerebellar afferent nerve. And then, “through learning” in the cerebellum, the cerebellum-reward-sensorimotor pathway (red line) may be responsible for projecting imitative signals to the sensorimotor and reward regions through the cerebellar efferent nerve and play a key role in the neuropathology of chronic itch. Green line: the sensory signal from skin to the cerebellum