Development of auditory function in the tammar wallaby Macropus eugenii

Hill, Kenneth G. and Cone-Wesson, Barbara and Liu, Guang-Bin (1998) Development of auditory function in the tammar wallaby Macropus eugenii. Hearing Research, 117 (1-2). pp. 97-106. ISSN 0378-5955

Abstract

Auditory brainstem responses (ABRs) were evoked in developing wallabies by click and tone burst stimuli delivered by bone conduction and air conduction, at progressive stages of post-natal (pouch) life. ABRs were recorded through the onset of auditory responses (95–110 days), the opening of the external ear canal (125–130 days) and the maturation of ABR thresholds and latencies to values corresponding to those in adults (>180 days). ABRs were evoked in response to bone-conducted clicks some days prior to the age at which an acoustically evoked response was first observed (around 95 days of pouch life). ABRs could be evoked by bone-conducted and intense air-conducted stimuli prior to opening of the ear canal. A trend of decreasing threshold and latency with age was observed for both modes of stimulation. The morphology of the ABR became more complex, according to both increased age and increased stimulus intensity. The ABR waveforms indicated relatively greater mechanosensitivity to bone-conducted stimuli than to air-conducted stimuli, prior to opening of the ear canal. Following opening of the ear canal, thresholds to air-conducted clicks and tones were substantially reduced and decreased further over the next 10–20 days, while thresholds to bone-conducted clicks continued slowly to decrease. Thresholds to tone bursts in the centre frequency range (4–12 kHz) remained less than those for low (0.5–1.5 kHz) and higher (16 kHz) frequencies. Latencies of an identified peak in ABR waveforms characteristically decreased with age (at constant stimulus intensity) and with stimulus intensity (for a given age). ABR waveforms obtained at progressive ages, but judged to be at corresponding sensation levels, underwent maturational changes, independent of conductive aspects of the wallabies' hearing, for 2–3 weeks after opening of the ear canal.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty / Department / School: No Faculty
Date Deposited: 14 Dec 2017 02:19
Last Modified: 18 Dec 2017 05:24
Uncontrolled Keywords: Auditory development; Auditory brainstem response; Marsupial development
Fields of Research : 06 Biological Sciences > 0606 Physiology > 060603 Animal Physiology - Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970106 Expanding Knowledge in the Biological Sciences
Identification Number or DOI: 10.1016/S0378-5955(97)00211-6
URI: http://eprints.usq.edu.au/id/eprint/7596

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