Prepulse Inhibition (PPI). The startle reflex is a basic response to strong external stimuli. The acoustic startle response is a protective behavioral reaction consisting of muscle contractions of the eyelid, neck and extremities that is elicited by sudden, loud acoustic stimuli. Typically whole body startle to a loud acoustic stimulus is measured by placing an animal into a holder that is attached to a transducer platform which measures maximum startle response force and timing. A weak sound preceding the loud acoustic startle inhibits the startle reflex. This is called pre-pulse inhibition. Pre-pulse inhibition is the decrease in startle magnitude by a pre-pulse presented shortly before the startle stimulus that does not elicit a startle response itself.
Each session starts with a 5 min acclimatization period during which a 65-dB background noise plays continuously. Following acclimatization a total of 54 trials are presented to the animal. Six different trial types are randomly assigned and delivered (approximately every 15-20 s) for 9 times throughout the session: 40 ms 120 dB burst (pulse alone), 65 dB background noise (noise alone), and 20 ms pre-pulse of 70, 76, 82 and 88 dB followed 100 ms by a 40 ms 120 dB pulse.
The PPI equipment in the Rat Neurobehavioral Laboratory is manufactured by San Diego Instruments. We have eight test stations, the isolation chambers measure 11.25 x 11.25”, the animal enclosure 8” L x 3.5 “diameter.
- Mark A. Geyer and Neal R. Swerdlow (2001) Measurement of startle response, prepulse inhibition and habituation. Current Protocols in Neuroscience. 3:8.7.1-8.7.15.