Email updates

Keep up to date with the latest news and content from BMC Neuroscience and BioMed Central.

This article is part of the supplement: Twentieth Annual Computational Neuroscience Meeting: CNS*2011

Open Access Poster presentation

A biophysically detailed model of the primary auditory cortex explains physiological forward masking, co-tuning of excitation and inhibition and cortical signal amplification

Johan P Larsson1*, Ernest Montbrió1 and Gustavo Deco12

Author Affiliations

1 Computational Neuroscience Group, Universitat Pompeu Fabra, 08018 Barcelona, Spain

2 Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain

For all author emails, please log on.

BMC Neuroscience 2011, 12(Suppl 1):P66  doi:10.1186/1471-2202-12-S1-P66


The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2202/12/S1/P66


Published:18 July 2011

© 2011 Larsson et al; licensee BioMed Central Ltd.

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Poster presentation

For a long time, studies argued for inhibition as the main mechanism responsible for two-tone suppression (a.k.a. forward masking) seen in primary auditory cortex (A1) neurons [1,2]. However, both computational [3] and experimental [4] papers afford a significant role to thalamocortical (ThC) synaptic depression in shaping the temporal response properties of A1. Also, the duration of inhibitory currents in A1 has been an issue of contention [6,7]. Another study of forward masking [5] used noise click stimuli to show that while responses to the probe were not fully recovered even 512 ms after presentation of the masker, inhibitory currents evoked by the masker lasted at most 100 ms, coinciding in duration with the complete suppression of probe responses. The authors proposed that a longer-lasting mechanism such as ThC or intracortical (IC) synaptic depression could complement inhibition by accounting for the lingering effect seen. They also demonstrated that pentobarbital anesthesia significantly prolongs inhibition, thus calling into question results such as [1,2]. Here we present a biophysically detailed, tonotopically organized network model of A1, which employs Hodgkin and Huxley neurons with stochastic synaptic depression in ThC synapses. Our model accounts for forward masking seen with both single tones [1,2] and noise stimuli [5], while showing approximately balanced excitation and inhibition [7-9]. Inspired by [10], we propose a plausible IC connectivity for the layers III and IV of A1, which selectively amplifies the broad input from the thalamus to yield the sharp frequency tuning seen in many studies of A1. We conclude that a combination of IC currents and ThC synaptic depression is imperative for accounting for the wealth of data seen in the neurophysiological literature, such as the phenomena we study here.

Acknowledgements

E.M., J.P.L. and G.D. acknowledge the financial support of the European research project EmCAP (FP6-IST, Contract No. 013123).

References

  1. Calford MB, Semple MN: Monaural inhibition in cat auditory cortex.

    J. Neurophysiol 1995, 75:1876-1891. OpenURL

  2. Brosch M, Schreiner CE: Time course of forward masking tuning curves in cat primary auditory cortex.

    J. Neurophysiol 1997, 77:923-943. PubMed Abstract | Publisher Full Text OpenURL

  3. Denham SL: Cortical synaptic depression and auditory perception. In Computational models of auditory function. Volume 312. Edited by S. Greenberg and M. Slaney. Amsterdam: NATO Science Series: Life Sciences, IOS; 2001::281-296. OpenURL

  4. Rose HJ, Metherate R: Auditory Thalamocortical Transmission Is Reliable and Temporally Precise.

    J. Neurophysiol 2005, 94:2019-2030. PubMed Abstract | Publisher Full Text OpenURL

  5. Wehr M, Zador AM: Synaptic mechanisms of forward suppression in rat auditory cortex.

    Neuron 2005, 47:437-445. PubMed Abstract | Publisher Full Text OpenURL

  6. Tan AYY, Zhang LI, Merzenich MM, Schreiner CE: Tone-evoked excitatory and inhibitory synaptic conductances of primary auditory cortex neurons.

    J. Neurophysiol 2004, 92:630-643. PubMed Abstract | Publisher Full Text OpenURL

  7. Wehr M, Zador AM: Balanced inhibition underlies tuning and sharpens spike timing in auditory cortex.

    Nature 2003, 426:442-446. PubMed Abstract | Publisher Full Text OpenURL

  8. Wu GK, Arbuckle R, Liu B, Tao HW, Zhang LI: Lateral sharpening of cortical frequency tuning by approximately balanced inhibition.

    Neuron 2008, 58:132-143. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  9. Tan AYY, Wehr M: Balanced tone-evoked synaptic excitation and inhibition in mouse auditory cortex.

    Neuroscience 2009, 163:1302-1305. PubMed Abstract | Publisher Full Text OpenURL

  10. Liu B, Wu GK, Arbuckle R, Tao HW, Zhang LI: Defining cortical frequency tuning with recurrent excitatory circuitry.

    Nat. Neurosci 2007, 10:1594-1600. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL