title: Effect of preceding stimulation on sound localization and its representation in the auditory midbrain.
abstract: Prior stimulation can influence the perception of sound source location. Some psychophysical sound localization procedures differ in the amount of prior stimulation, which may affect measures of localization accuracy. If and how particularly the number of preceding stimuli affects sound localization and the neural representation of sound source position has not been investigated so far and will be the focus of the present report. We trained Mongolian gerbils in a left/right discrimination task where the target stimulus was preceded by silence or followed a number of reference stimuli. Localization thresholds decreased with the number of references presented before the target stimulus. The smallest thresholds were found after the presentation of a train of 5 reference stimuli and after silence. We recorded from units in the inferior colliculus (IC) of anaesthetized gerbils using virtual-acoustic space stimuli mimicking the ones used in the behavioural task and applied signal detection theory to compare behavioural and neurometric thresholds. We found that neurometric thresholds based on spike rate information of single units covered a wide range of threshold values but only neurometric thresholds that were based on responses of small populations of IC units reached consistently thresholds we also observed in the behavioural experiment. Unlike behavioural thresholds, however, neurometric thresholds were independent of the number of reference stimuli suggesting that processing stages downstream from the IC might better reflect the effect of prior stimulation.
authors.affiliation: Cluster of Excellence Hearing4all, Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, Oldenburg, D-26111, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Tolnai
authors.affiliation: Cluster of Excellence Hearing4all, Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, Oldenburg, D-26111, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Beutelmann
authors.affiliation: Cluster of Excellence Hearing4all, Animal Physiology and Behaviour Group, Department of Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, Oldenburg, D-26111, Germany.
authors.forename: Georg M
authors.initials: GM
authors.lastname: Klump
mesh_terms: D000818:Animals; D001309:Auditory Threshold; D003214:Conditioning, Classical; D004192:Discrimination, Psychological; D005260:Female; D005849:Gerbillinae; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D013017:Sound Localization
keywords: Mongolian gerbil; free-field sound localization; population coding; signal detection theory