An estimate of the auditory-filter bandwidth in the Mongolian gerbil

Critical ratios (CRs) and the critical band (CB) were determined in six Mongolian gerbils (Meriones unguiculatus) using a GO/NOGO procedure and the method of constant stimuli. The test-tone frequencies were 0.5, 1, 2, 4 and 8 kHz in the CR measurements and 2 kHz in the CB measurement. Critical ratios were independent of the level of the white-noise masker. The lowest CR with a mean of 24.8 dB was found at 1 kHz for maskers with spectrum levels of 20 and 40 dB SPL. The CR increased on average by 2.1 dB per octave between the frequencies 1 and 4 kHz. The CR bandwidth at 2 kHz and at a masker spectrum level of 40 dB SPL was 417 Hz. Using the band-narrowing procedure, we determined a mean CB of 216 Hz at a test-tone frequency of 2 kHz. The results are discussed in comparison to psychophysical data from other rodent species and humans. Finally, the relation of CR and CB bandwidths to the bandwidth of tuning curves of gerbil auditory-nerve fibers and the gerbil's cochlear frequency map are explored.