Evidence for a neural source of the precedence effect in sound localization

Andrew D. Brown, Heath G. Jones, Alan Kan, Tanvi Thakkar, G. Christopher Stecker, Matthew J. Goupell, Ruth Y. Litovsky

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Normal-hearing human listeners and a variety of studied animal species localize sound sources accurately in reverberant environments by responding to the directional cues carried by the first-arriving sound rather than spurious cues carried by later-arriving reflections, which are not perceived discretely. This phenomenon is known as the precedence effect (PE) in sound localization. Despite decades of study, the biological basis of the PE remains unclear. Though the PE was once widely attributed to central processes such as synaptic inhibition in the auditory midbrain, a more recent hypothesis holds that the PE may arise essentially as a by-product of normal cochlear function. Here we evaluated the PE in a unique human patient population with demonstrated sensitivity to binaural information but without functional cochleae. Users of bilateral cochlear implants (CIs) were tested in a psychophysical task that assessed the number and location(s) of auditory images perceived for simulated source-echo (lead-lag) stimuli. A parallel experiment was conducted in a group of normal-hearing (NH) listeners. Key findings were as follows: 1) Subjects in both groups exhibited lead-lag fusion. 2) Fusion was marginally weaker in CI users than in NH listeners but could be augmented by systematically attenuating the amplitude of the lag stimulus to coarsely simulate adaptation observed in acoustically stimulated auditory nerve fibers. 3) Dominance of the lead in localization varied substantially among both NH and CI subjects but was evident in both groups. Taken together, data suggest that aspects of the PE can be elicited in CI users, who lack functional cochleae, thus suggesting that neural mechanisms are sufficient to produce the PE.

Original languageEnglish (US)
Pages (from-to)2991-3001
Number of pages11
JournalJournal of Neurophysiology
Issue number5
StatePublished - Sep 23 2015
Externally publishedYes


  • Cochlear implants
  • Precedence effect
  • Sound localization

ASJC Scopus subject areas

  • General Neuroscience
  • Physiology


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