Head-twitch response

The head-twitch response (HTR) is a rapid side-to-side head movement that occurs in mice and rats after the serotonin 5-HT2A receptor is activated. The prefrontal cortex may be the neuroanatomical locus mediating the HTR. Many serotonergic hallucinogens, including lysergic acid diethylamide (LSD), induce the head-twitch response, so the HTR is used as a behavioral model of hallucinogen effects.