Age-Dependent Changes of Gap Detection in the Mongolian Gerbil ( Meriones unguiculatus )

Abstract

Gap detection using broadband noise was characterized in a group of young gerbils from the breeding colony of the University of Regensburg (RB gerbils), old RB gerbils, and old gerbils from the breeding colony of the University of South Carolina (SC gerbils). Data from old RB and old SC gerbils were not significantly different and were subsequently combined for a comparison with data from the group of young RB gerbils. Level dependence of gap-detection thresholds in young and old domesticated gerbils resembled the typical mammalian pattern of level dependence. Gap-detection thresholds of old gerbils were significantly elevated at 30 dB SL and 50 dB SPL as compared with young gerbils. Compared with young gerbils tested at 30 dB SL and 50 dB SPL, the distribution of gap-detection thresholds in old gerbils was broader with a spread to higher gap-detection thresholds. Some old animals retained excellent temporal resolution, while some showed impaired gap detection. The gap-detection data collected in young and old gerbils resemble previously published data from humans of different age and confirm that gerbils are a useful model to study age-dependent changes in temporal processing.

Age-related changes in auditory temporal processing in the rat

“…The age-related increase in the gap detection threshold (1.8 ms in young and 3.4 ms in old rats) had a similar magnitude as reported in mice [28], gerbils [29] and man [4,5,10,14]. For example, the mean GDT values for young and old gerbils were 2.6 ms and 4.3 ms, respectively [29], and for young and old human subjects the mean GDT values were 2.8 and 6.7 ms, respectively [14]. These data support the idea that the age-related deficit in gap detection may have a common mechanism in mammals of different species.…”

“…The same phenomenon of increased GDT variability in elderly subjects was also observed in gerbils [29], mice [28] and in man [9,28] Several studies have demonstrated that the intensity and frequency content of the carrier noise play an important role in gap detection: GDT values markedly increase (both in man and in animals) when the signal audibility is low (when the noise intensity is less than 25-30 dB sensation level) or when the noise spectrum is restricted to low frequencies [1,8,18,45].…”

“…Similarly as in normal hearing subjects, an intensity of the carrier sound above a 20-30 dB sensation level is required for reliable GDT measurements in old [29] as well as in hearing-impaired subjects [18,46]. With respect to the results of our previous study [47] and the results of other authors showing that the increase of hearing thresholds in old rats amounts to 30-40 dB [34,48,49], we measured GDT and GDDL at a carrier noise intensity of 75 dB SPL.…”

“…As a behavioral method for assessing auditory temporal resolution in animals, the gap detection task has been frequently used (e.g., rat [17][18][19], mice [20,21], chinchilla [22,23]; ferret [23], gerbil [25], starling [26], budgerigar and zebra finch [27]. A deficit in gap detection with aging was demonstrated in mice [20,28] and gerbils [29].…”

The Mongolian Gerbil as a Model for the Analysis of Peripheral and Central Age-Dependent Hearing Loss

“…In addition to measuring threshold for the detection of signals in quiet, more complex tasks require the detection of a stimulus that deviates form a constantly and repeatedly presented background stimulus. This approach has been used to characterise the ability to discriminate between synthetic speech-like stimuli (Sinnott & Mosqueda, 2003), determine the minimum audible gap duration in a broadband noise pulse (Hamann et al, 2004) and characterise forward masking (Gleich et al, 2007a) in gerbils.…”