Multimodal Interactions: Pain-Touch

While injecting local anesthetic into a patient's gum, the dentist may grab the patient's cheek and shake it with his or her other hand. This greatly reduces the pain of the injection. The sensory signals produced by shaking, which may be considered a rather vigorous form of touch, are somehow blocking the pain the patient would otherwise feel. Patrick Wall and Ronald Melzack explained this suppression by proposing that pain signals must pass through a neural “gate” in the spinal cord if they are to reach the brain, and that touch signals are sometimes able to close this gate. Later work has broadly confirmed this gate control theory, while refining our understanding of how gating works.

Pain gating is possible because of the distinctive anatomy of ...