Sensorimotor Gating

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.