Startle response and its prepulse modification in health and under different psychopathologies: Could we find any specific patterns?

The startle response (SR) is a generalized defensive response elicited by the presentation of a sudden intense stimulus. The presentation of a less intense signal (prepulse) before the central stimulus (pulse) affects the amplitude and latency of SR differently depending on the prepulse lead interval. The most studied form of such changes is prepulse inhibition (PPI), i.e. a decrease in SR amplitude at lead intervals of 50-500 ms. Prepulse facilitation, i.e. an increase in SR amplitude, can also be observed at lead intervals of 2000-4500 ms. The PPI deficiency has been found in a variety of psychopathologies and it has been suggested that it is a transdiagnostic phenomenon. However, some data from the literature support the existence of specific different nosologies, such as neurophysiological, neurochemical and molecular mechanisms that cause PPI lowering and affect prepulse facilitation of SR. This review provides a comparative analysis of studies on SR prepulse modification in healthy subjects and different groups of patients with mental or neurological disorders. The results of such an analysis may help to define directions for further research to improve methods of early diagnosis and to improve the validity of translational models.