Acoustic Startle and Pre-pulse Inhibition (PPI) 2.4 The acoustic startle response is characterized by an exaggerated flinching response to an unexpected strong auditory stimulus (pre-pulse). This response can be attenuated when it is preceded by a weaker stimulus (pre-pulse) and is the principle underlying pre-pulse inhibition (PPI). PPI has been described in numerous species, including mice and humans and provides an operational measure of sensorimotor gating reflecting the ability of an animal to successfully integrate and inhibit sensory information. Several clinical studies have shown that a number of human disorders have impaired PPI including: schizophrenia, Huntington’s disease, fragile X syndrome, and autism. The acoustic startle and PPI paradigm is therefore largely used to assess sensorimotor gating and the effects of a number of treatment modalities such as putative anti-psychotics, and to explore genetic and neurobiological mechanisms underlying behaviors of relevance to psychosis (Geyer, 1999; Ouagazzal et al., 2001).Ontological description: MP:0002067 - abnormal sensory capabilities/reflexes/nociception. true IMPC_ACS_002 Adult Week 10