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Sound localization in reverberant environments: physiological bases of the precedence effect.

Paterson, M.A.M.; (2005) Sound localization in reverberant environments: physiological bases of the precedence effect. Doctoral thesis , University of London. Green open access

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Abstract

Localization dominance, a phenomenon of the precedence effect, refers to the dominance of directional cues conveyed by sound arriving directly from the source over cues conveyed by reflected copies on the perception of sound source location. One theory of localization dominance is that leading sounds suppress neural responses to lagging sounds (Yin, 1994 Litovsky & Yin, 1998 a, b). Neurons in auditory nuclei respond best to a leading sound and have a reduced response to a lagging sound, supporting this hypothesis. It has been proposed that GABA-ergic or glycinergic inhibition suppresses neural responses to lagging sounds (Yin, 1994 Fitzpatrick et al. 1995 Pollack & Burger, 2002). An alternative hypothesis states that cochlear processing in low-frequency hearing animals alters directional cues conveyed by the leading and lagging sound, emphasising those present in the leading sound (Tollin, 1998 Hartung & Trahiotis 2001). Responses of single neurons in the inferior colliculus (IC) of anaesthetised guinea pigs were recorded to binaural click pair stimuli. Responses of some neurons were recorded before, during, and after iontophoresis of either the GABAa receptor antagonist gabazine, or the glycine receptor antagonist strychnine. Blocking glycine did not decrease neural suppression of the lagging click in 8/10 neurons. Blocking GAB A did not decrease neural suppression of the lagging click in 11/16 neurons. The neural representation of directional cues in the output of low-frequency neurons to the leading click of a binaural click pair differed from those actually conveyed by the stimulus in 20/20 neurons. Examination of the responses of several such neurons indicated responses to the leading click represented a direction between that conveyed by the leading and lagging click. The results supported the hypothesis that cochlear processing of binaural click pairs alters directional cues conveyed by the stimulus. Limited support was also found for the hypothesis that GABA-ergic and glycinergic suppress lagging click responses in some neurons.

Type: Thesis (Doctoral)
Title: Sound localization in reverberant environments: physiological bases of the precedence effect.
Identifier: PQ ETD:593224
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by Proquest
UCL classification: UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Neuro, Physiology and Pharmacology
URI: http://discovery.ucl.ac.uk/id/eprint/1445900
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