Although scratching has been everyone’s favorite method of removing an itch for thousands if not millions of years, scientists have not been able to uncover the neurological mechanism of this action. Now a team of University of Minnesota researchers used the long-tailed macaques as subjects in an experiment that showed that the nerves being scratched send different signals to the spinal cord and then to the brain depending on whether there’s an itch in the area. In addition to being a peculiar finding, this may lead to the development of stimulation devices that address acute itching, pain, or other nociceptive phenomena.
From the abstract in Nature Neuroscience:
Spinothalamic tract (STT) neurons respond to itch-producing agents and transmit pruritic information to the brain. We observed that scratching the cutaneous receptive field of primate STT neurons produced inhibition during histamine-evoked activity but not during spontaneous activity or activity evoked by a painful stimulus, suggesting that scratching inhibits the transmission of itch in the spinal cord in a state-dependent manner.
Abstract in Nature Neuroscience: Relief of itch by scratching: state-dependent inhibition of primate spinothalamic tract neurons
(hat tip: AP)