Ultrasonic vocalizations elicit orienting and associative reactions in preweanling mice

On postnatal days (PND) 12 and 13, 90 male Swiss CD-1 mice were tested for orientation to 3 intensities of recorded ultrasounds while climbing an inclined wire grid surface. Motor responses and vocalization to replayed ultrasounds (55-75 kHz) of 20-, 40-, and 60-dB SPL indicated an intensity dependence. In Experiment 2, 138 pups were exposed to either contingent or noncontingent pairings of recorded ultrasounds of 55-75 kHz, averaging 40 dB, and mild inescapable footshocks, or taped vocalizations or footshocks only on PND 12, 14, or 16. At PND 18, subjects were tested for passive avoidance following exposure to the taped ultrasounds only upon entry into the dark side of a black-white compartment. Results suggested only overall, nonspecific effects of pretreatment to elicit responses antagonistic to motor activity. In Experiment 3, 36 pups at PND 15 were tested for passive avoidance with the ultrasound recordings of 40- or 80-dB onset upon entry to the dark compartment; a third group had no ultrasound exposure. A significant intensity effect confirmed that the ultrasounds had prepotent properties.