Abstract
For over a century, the Duplex theory has posited that low- and high-frequency sounds are localized using two different acoustical cues, interaural time (ITDs) and level (ILDs) differences, respectively. Psychophysical data have generally supported the theory for pure tones. Anatomically, ITDs and ILDs are separately encoded in two parallel brainstem pathways. Acoustically ILDs are a function of location and frequency such that lower and higher frequencies exhibit smaller and larger ILDs, respectively. It is well established that neurons throughout the auditory neuraxis encode high-frequency ILDs. Acoustically, low-frequency ILDs are negligible (∼1–2 dB); however, humans are still sensitive to them and physiological studies often report low-frequency ILD-sensitive neurons. These latter findings are at odds with the Duplex theory. We suggest that these discrepancies arise from an inadequate characterization of the acoustical environment. We hypothesize that low-frequency ILDs become large and useful when sources are located near the head. We tested this hypothesis by making measurements of the ILDs in chinchillas as a function of source distance and the sensitivity to ILDs in 103 neurons in the inferior colliculus (IC). The ILD sensitivity of IC neurons was found to be frequency independent even though far-field acoustical ILDs were frequency dependent. However, as source distance was decreased, the magnitudes of low-frequency ILDs increased. Using information theoretic methods, we demonstrate that a population of IC neurons can encode the full range of acoustic ILDs across frequency that would be experienced as a joint function of source location and distance.
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References
Barlow H (1961) Possible principles underlying the transformation of sensory messages. In: Rosenblith, W (ed) Sensory Communication. Wiley, New York
Benson DA, Teas DC (1976) Single unit study of binaural interaction in the auditory cortex of the chinchilla. Brain Res 103:313–338
Brungart DS, Rabinowitz WM (1999) Auditory localization of nearby sources. Head-related transfer functions. J Acoust Soc Am 106:1465–1479
Dayan P, Abbott LF (2001) Theoretical neuroscience: computational and mathematical modeling of neural systems. MIT Press, Cambridge, MA
Duda RO, Martens WL (1998) Range dependence of the response of a spherical head model. J Acoust Soc Am 104:3048–3058
Hafter ER (1984) Spatial hearing and the Duplex theory: how viable is the model. In: Edelman GM, Gall WE, Cowan WM (eds) Dynamic aspects of neocortical function. Wiley, New York, pp 425–448
Heffner RS, Heffner HE, Kearns D, Vogel J, Koay G (1994) Sound localization in chinchillas. I: left/right discriminations. Hear Res 80:247–257
Kim DO, Bishop B, Kuwada S (2010) Acoustic cues for sound source distance and azimuth in rabbits, a racquetball and a rigid sphere. J Assoc Res Otolaryngol 11:541–557
Koka K, Jones HG, Thornton JL, Lupo JE, Tollin DJ (2011) Sound pressure transformations by the head and pinnae of the adult Chinchilla (Chinchilla lanigera). Hear Res 272:135–147
Macpherson EA, Middlebrooks JC (2002) Listener weighting of cues for lateral angle: the Duplex theory of sound localization revisited. J Acoust Soc Am 111:2219–2236
Rayleigh L (1907) On our perception of the direction of a source of sound. Philos Mag 13:214–232
Sanes DH, Rubel EW (1988) The ontogeny of inhibition and excitation in the gerbil lateral superior olive. J Neurosci 8:682–700
Semple MN, Kitzes LM (1987) Binaural processing of sound pressure level in the inferior colliculus. J Neurophysiol 57:1130–1147
Zahorik P (2002) Assessing auditory distance perception using virtual acoustics. J Acoust Soc Am 111:1832–1846
Acknowledgement
This research was supported by NIH R01-DC011555 (DJT).
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Jones, H.G., Koka, K., Thornton, J., Tollin, D.J. (2013). The Sound Source Distance Dependence of the Acoustical Cues to Location and Their Encoding by Neurons in the Inferior Colliculus: Implications for the Duplex Theory. In: Moore, B., Patterson, R., Winter, I., Carlyon, R., Gockel, H. (eds) Basic Aspects of Hearing. Advances in Experimental Medicine and Biology, vol 787. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-1590-9_31
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DOI: https://doi.org/10.1007/978-1-4614-1590-9_31
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