- Poster presentation
- Open Access
A biophysically detailed model of the primary auditory cortex explains physiological forward masking, co-tuning of excitation and inhibition and cortical signal amplification
© Larsson et al; licensee BioMed Central Ltd. 2011
- Published: 18 July 2011
- Primary Auditory Cortex
- Pentobarbital Anesthesia
- Synaptic Depression
- Inhibitory Current
- Noise Stimulus
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  and experimental  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  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 , while showing approximately balanced excitation and inhibition [7–9]. Inspired by , 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.
E.M., J.P.L. and G.D. acknowledge the financial support of the European research project EmCAP (FP6-IST, Contract No. 013123).
- Calford MB, Semple MN: Monaural inhibition in cat auditory cortex. J. Neurophysiol. 1995, 75: 1876-1891.Google Scholar
- Brosch M, Schreiner CE: Time course of forward masking tuning curves in cat primary auditory cortex. J. Neurophysiol. 1997, 77: 923-943.PubMedGoogle Scholar
- Denham SL: Cortical synaptic depression and auditory perception. Computational models of auditory function. Edited by: S. Greenberg and M. Slaney. 2001, Amsterdam: NATO Science Series: Life Sciences, IOS, 312: 281-296.Google Scholar
- Rose HJ, Metherate R: Auditory Thalamocortical Transmission Is Reliable and Temporally Precise. J. Neurophysiol. 2005, 94: 2019-2030. 10.1152/jn.00860.2004.View ArticlePubMedGoogle Scholar
- Wehr M, Zador AM: Synaptic mechanisms of forward suppression in rat auditory cortex. Neuron. 2005, 47: 437-445. 10.1016/j.neuron.2005.06.009.View ArticlePubMedGoogle Scholar
- 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. 10.1152/jn.01020.2003.View ArticlePubMedGoogle Scholar
- Wehr M, Zador AM: Balanced inhibition underlies tuning and sharpens spike timing in auditory cortex. Nature. 2003, 426: 442-446. 10.1038/nature02116.View ArticlePubMedGoogle Scholar
- 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. 10.1016/j.neuron.2008.01.035.PubMed CentralView ArticlePubMedGoogle Scholar
- Tan AYY, Wehr M: Balanced tone-evoked synaptic excitation and inhibition in mouse auditory cortex. Neuroscience. 2009, 163: 1302-1305. 10.1016/j.neuroscience.2009.07.032.View ArticlePubMedGoogle Scholar
- Liu B, Wu GK, Arbuckle R, Tao HW, Zhang LI: Defining cortical frequency tuning with recurrent excitatory circuitry. Nat. Neurosci. 2007, 10: 1594-1600. 10.1038/nn2012.PubMed CentralView ArticlePubMedGoogle Scholar
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 (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.