Skip to main content
  • Poster presentation
  • Open access
  • Published:

Modeling sound pulse counting in inferior colliculus

The ability of animals to count events or objects and its underlying mechanisms – including the possible existence of a dedicated “number sense” – is a topic of much recent fascination and research interest. A simple computation that frogs execute routinely is counting the number of consecutive sound pulses in a conspecific call that occur with precise and regular timing [1]. Cells signaling that a threshold number of pulses have occurred have been found in the midbrain of anurans [2]. These counting cells will not respond if a single inter-pulse interval is a few milliseconds longer than the baseline interval. What intrinsic or network mechanisms can give rise to such pulse/interval counting? Comparing simplified neuron models with previously published in vivo membrane potential recordings [3], we identify biophysical processes that can explain the observations. First, we consider a model of phasic inhibition made of onset and offset inhibition. Phasic inhibition enhances reset because a longer interval will engender onset and possibly offset inhibition. Second, we consider four mechanisms, namely short-term facilitation of excitation, persistent sodium currents, dendritic NMDA synapses and recurrent connections of cells imbedded in a network. Combining phasic inhibition with either of these mechanisms can qualitatively reproduce the array of recordings for different pulse patterns – including those with pauses that reset the counting – as well as the effect of pharmacologically attenuating inhibition. These results support the hypothesis that prior segmentation of sound via phasic on and off responses underlies the emergence of features such as pulse counting and duration selectivity in the auditory midbrain.

Figure 1
figure 1

Membrane potential response of counting neurons to series of sound pulses. From left to right columns correspond to: experiments, the persistent sodium model, the short-term plasticity model and the dendritic NMDA model.


  1. Klump GM, Gerhardt HC: Use of non-arbitrary acoustic criteria in mate choice by female gray tree frogs. Nature. 1987, 326: 286-288. 10.1038/326286a0.

    Article  Google Scholar 

  2. Edwards CJ, Alder TB, Rose GJ: Auditory midbrain neurons that count. Nat Neurosci. 2002, 5 (10): 934-936. 10.1038/nn916.

    Article  CAS  PubMed  Google Scholar 

  3. Edwards CJ, Leary CJ, Rose GJ: Counting on inhibition and rate-dependent excitation in the auditory system. J Neurosci. 2007, 27 (49): 13384-13392. 10.1523/JNEUROSCI.2816-07.2007.

    Article  CAS  PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Richard Naud.

Rights and permissions

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Naud, R., Houtman, D., Rose, G.J. et al. Modeling sound pulse counting in inferior colliculus. BMC Neurosci 15 (Suppl 1), P113 (2014).

Download citation

  • Published:

  • DOI: