Mongolian gerbil neonates were studied with respect to auditory sensitivity and the changes of selected structures of the external, middle, and inner ear. The data demonstrate an improvement in sensitivity to sound associated with postnatal changes in the morphology of the ear. Cochlear potentials and a concomitant reflex response to sound were observed 14 days after birth. At this state of postnatal development the organ of Corti appeared mature, the external auditory canal was open, but mesenchyme was present within the tympanic bulla.

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The Mongolian gerbil is native to the region of the Gobi Desert. The gerbil cochlear and vestibular elements are unusually well exposed for study and experimental investigation. This report depicts several features of the gross and microscopic anatomy of the gerbil and describes its auditory sensitivity by the cochlear-potential method. Criterion cochlear potentials (0.5 μV) range from 50 dB at 200 Hz to 60 dB at 30 000 Hz. In the regions of 1000 and 4000 Hz cochlear sensitivity is seen at 15 and 0 dB SPL, respectively. Comparisons are made between gerbil cochlear responses and responses from other small rodents. [Research supported by the National Institutes of Neurological Diseases and Blindness, U. S. Department of Health, Education and Welfare.]