Sensitivity to High Frequency Communication Sounds in the Inner Ear Enhanced by Selective Attention: Preliminary Findings in Mongolian Gerbils

Abstract

Audible range for Mongolian gerbils overlaps well with one for humans. This is one of the reasons why they have been used for auditory studies. So, most of studies on gerbils have been in human audible frequency range. They live in a group and use a variety of vocalizations for their conspecific communication. Roughly 80% of the fundamental frequencies of their communication calls are found in the frequency range above 20kHz. However, thresholds for frequencies above 20kHz have been reported higher than those for low frequencies (from 1kHz to 16kHz) by as much as 20dB. We examined how gerbils utilize ultrasonic frequency range for their important vocal communication. Findings from alert animals with paired condition showed the cochlear microphonics (CM) were amplified by 2-4dB with ultrasonic communication calls of low sound pressure levels (from 45dB to 60dB p.e. SPL), while no enhancement was observed with the same calls higher than 65dB p.e. SPL. Findings also suggested that CM responses to tone burst higher than 25kHz demonstrated magnified amplitude under the paired condition. Data strongly imply that attention to conspecifics would increase sensitivity to ultrasonic frequency range.