Spatial hearing and temporal processing ability of the Mongolian gerbil (Meriones unguiculatus) measured using prepulse inhibition of acoustic startle.

The Mongolian gerbil is a common model organism for studying the neural and behavioral mechanisms of binaural and spatial hearing, largely because of its ability to hear lower frequencies better than other rodents and thus utilize both interaural time and level difference cues for sound localization. Prior spatial hearing studies in gerbils have relied on operant conditioning paradigms, requiring large amounts of time-consuming training and testing on multiple different tasks needed to make a comprehensive assessment of spatial hearing ability (including temporal processing, spatial acuity and spatial unmasking). This limits the ability of researchers to thoroughly assess behavioral performance in a population of animals. In this study, we used the prepulse inhibition of the acoustic startle reflex (PPI) to extensively assess spatial hearing and temporal processing abilities in a population of gerbils of both sexes. Results show that gerbils inhibit a startle response to a brief loud sound based on prepulse acoustical cues consisting of a 1) temporal gap in ongoing sounds, 2) change in sound source location, and 3) target sound in the presence of a masker. In each test, the magnitude of the suppression of startle increased monotonically as a function of the magnitude of the acoustical prepulse, not unlike a psychometric function, from which threshold performance could be measured. Thresholds in the gerbils in each task measured using PPI matched those acquired using operant conditioning methods.