Responsiveness to natural vs. artificial sounds in “wild” vs. in-bred mice
Pre-pulse inhibition (PPI) has been well studied in mice, and is the term used when a mouse has a reduced startle reflex due to the presence of a non-startling pre-pulse stimulus. This research study focused on auditory pre-pulse stimuli. In the Computational, Speech, Sensory, Development and Diseases Lab at James Madison University, where this study was completed, the startle-eliciting stimulus is a short and loud burst of white noise (15 ms, 110 dB (SPL)). It is known that an artificial auditory stimulus, such as the onset or offset of white noise, can be an effective pre-pulse cue. This study shows that an auditory stimulus that is more ecologically relevant to the mice is effective in eliciting pre-pulse inhibition. PPI was tested in both male and female Mus musculus of C57BL/6J strain and Peromyscus maniculatus. The pre-pulse stimuli included male Mus calls and pure tones of high, mid, and low-frequencies. While the calls inhibited the startle of the Mus, the high and low- frequency tones actually increased the startle of the Peromyscus. The Mus only tended toward negative PPI to the low-frequency tones, and it was not significant. The Peromyscus displayed negative PPI to both low and high-frequency tones, yet it was only significant in the low-frequency tones. Differences between sexes were also measured, but there were no statistically significant differences. These findings suggest that naturalistic stimuli should be used in perceptual studies of mice and there should be further investigation into the causes of negative PPI in Peromyscus.