Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds II

Single-neuron recordings

Mathias Dietz*, Torsten Marquardt, Annette Stange, Michael Pecka, Benedikt Grothe, David McAlpine

*Corresponding author for this work

Research output: Contribution to journalArticle

24 Citations (Scopus)


Recently, with the use of an amplitude-modulated binaural beat (AMBB), in which sound amplitude and interaural-phase difference (IPD) were modulated with a fixed mutual relationship (Dietz et al. 2013b), we demonstrated that the human auditory system uses interaural timing differences in the temporal fine structure of modulated sounds only during the rising portion of each modulation cycle. However, the degree to which peripheral or central mechanisms contribute to the observed strong dominance of the rising slope remains to be determined. Here, by recording responses of single neurons in the medial superior olive (MSO) of anesthetized gerbils and in the inferior colliculus (IC) of anesthetized guinea pigs to AMBBs, we report a correlation between the position within the amplitude-modulation (AM) cycle generating the maximum response rate and the position at which the instantaneous IPD dominates the total neural response. The IPD during the rising segment dominates the total response in 78% of MSO neurons and 69% of IC neurons, with responses of the remaining neurons predominantly coding the IPD around the modulation maximum. The observed diversity of dominance regions within the AM cycle, especially in the IC, and its comparison with the human behavioral data suggest that only the subpopulation of neurons with rising slope dominance codes the sound-source location in complex listening conditions. A comparison of two models to account for the data suggests that emphasis on IPDs during the rising slope of the AM cycle depends on adaptation processes occurring before binaural interaction.

Original languageEnglish
Pages (from-to)1973-1985
Number of pages13
JournalJournal of Neurophysiology
Issue number10
Publication statusPublished - May 2014
Externally publishedYes


  • Binaural processing
  • Extracellular recordings
  • Inferior colliculus
  • Medial superior olive

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