¹Universitätsklinikum Freiburg, Fakultät für Medizin, Klinik für Hals-, Nasen- und Ohrenheilkunde, Sektion Experimentell-klinische Otologie, Neurobiologisches Forschungslabor, Freiburg, Deutschland
²Universitätsklinikum Freiburg, Fakultät für Medizin, Klinik für Hals-, Nasen- und Ohrenheilkunde, Sektion Cochlear Implant, Freiburg, Deutschland
³Chinese University of Hong Kong, Gerald Choa Neuroscience Institute, Hong Kong, Hong Kong
⁴Chinese University of Hong Kong, Department of Otolaryngology, Hong Kong, Hong Kong
⁵Universitätsklinikum Freiburg, Fakultät für Medizin, Klinik für Hals-, Nasen- und Ohrenheilkunde, Sektion Experimentell-klinische Otologie, Freiburg, Deutschland
⁶Universität Freiburg, Bernstein Center Freiburg, Fakultät für Biologie, Freiburg, Deutschland

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Horizontal sound localization is based on two important binaural cues: interaural time differences (ITDs) and interaural level differences (ILDs). In normal hearing (NH) adults, the ITD sensitivity threshold at 250 Hz is around 25–30 µs [1]. However, the sensitivity to binaural cues can be influenced by various factors such as hearing experience, developmental state or the type of the acoustic stimulus [2], [3], [4]. The development of ITD sensitivity across age and its dependency on stimulus parameters are still under research and were investigated in this study.

Eleven NH (<20 dB HL) children (Ø 9.05 years old) and 10 NH adults (Ø 34.03 years old) were tested on sound lateralization in a gamified setup using headphones. A 0.5 s long tone burst at 250 Hz and a rising slope of 4 ms or 100 ms was used as acoustic stimulus. Participants were tested for different ITDs of ±\'7b25, 50, 100, 200, 400, 800\'7d µs. ITD just-noticeable differences (JNDs) were calculated for the different test conditions using psychometric functions.

NH adults demonstrated significantly better ITD JNDs (Ø 64.79 µs) compared to NH children (Ø 93.61 µs) for both slope conditions. For NH children, ITD sensitivity showed a positive correlation with age under both test conditions, indicating developmental improvement. Notably, both cohorts exhibited significantly better ITD JNDs when the auditory stimuli were presented with a rising slope of 4 ms (children: Ø 92.07 µs, adults: Ø 55.78 µs) rather than 100 ms (children: Ø 113.89 µs, adults: Ø 73.28 µs).

In conclusion, auditory networks for ITD-based spatial hearing are still maturing in early childhood [DTW1] , resulting in significantly poorer ITD sensitivity compared to mature, adult networks. Regardless of developmental stage, better ITD sensitivity was achieved with auditory stimuli that contained strong onset ITD information (4 ms rising slope), confirming the importance of onset ITD sensitivity for optimal spatial hearing.

References

[1] Zwislocki J, Feldman RS. Just Noticeable Dichotic Phase Difference. J Acoust Soc Am. 1956;28:152-3.
[2] Syeda A, Nisha KV, Jain C. Age differences in binaural and working memory abilities in school-going children. Int J Pediatr Otorhinolaryngol. 2023 Aug;171:111652. DOI: 10.1016/j.ijporl.2023.111652
[3] Thavam S, Dietz M. Smallest perceivable interaural time differences. J Acoust Soc Am. 2019 Jan;145(1):458. DOI: 10.1121/1.5087566
[4] Greenberg D, Monaghan JJM, Dietz M, Marquardt T, McAlpine D. Influence of envelope waveform on ITD sensitivity of neurons in the auditory midbrain. J Neurophysiol. 2017 Oct 1;118(4):2358-70. DOI: 10.1152/jn.01048.2015