the scratch reflex is a response to activation of sensory neurons whose peripheral terminals are located on the surface of the body. some sensory neurons can be activated by stimulation with an external object such as a parasite on the body surface. alternatively, some sensory neurons can respond to a chemical stimulus that produces an itch sensation. during a scratch reflex, a nearby limb reaches toward and rubs against the site on the body surface that has been stimulated. the scratch reflex has been extensively studied to understand the functioning of neural networks in vertebrates. despite decades of research, key aspects of the scratch reflex are still unknown, such as the neural mechanisms by which the reflex is terminated.