Heterogeneity improves the encoding of natural stimuli in a neuronal population
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1
Ludwig-Maximilians-Universität München, Germany
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2
Bernstein Center for Computational Neuroscience, Germany
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3
Eberhard Karls Universität Tübingen, Germany
Neurons often show remarkable heterogeneity in terms of their response properties even if they belong to the same cell type. This heterogeneity can result from biophysical, anatomical or input differences. Theoretical studies have shown that heterogeneity can decorrelate the activity in a neuronal population and thereby increase its ability to carry information about the stimulus. Experimental evidence about whether and how this effect is exploited in neural systems, remains scarce to date.
We investigate this question in our model system, the weakly electric fish that uses an actively generated electric field (the electric organ discharge, EOD) for navigation as well as communication purposes. Via specialized electroreceptors distributed all over their body they sense modulations of this field. The behaviorally relevant amplitude modulations (AMs) result in communication contexts from the interaction with other fish, or in hunting tasks from prey. AMs are encoded in the activity of electroreceptor afferents of the P-type. P-units respond phase-locked and probabilistically to each EOD cycle and show prominent negative serial correlations between successive interspike intervals. They show a high degree of heterogeneity in both their baseline firing rate as well as their sensitivity and are thus well suited for studying possible functional roles of this heterogeneity.
We here analyze data from intracellular recordings of P-units as well as from computational simulations of a novel P-unit model. Using the model we apply targeted variations of model parameter to identify possible sources of the observed heterogeneity. Further, we examine the impact the heterogeneity has on the encoding of AM signals originating from communication signals. For both, cells and model, we find resonances of the responses to AMs matching their baseline frequencies and its harmonics. These resonances are known to degrade the encoding of the AM stimuli. Because of the heterogeneity in their baseline firing rate each cell has its resonance peaks at different frequencies. Pooling over this heterogenous population averages these resonance peaks away and ensures that all frequencies are equally well represented in the population. Furthermore, the heterogeneity in the sensitivity of the cells ensures that communication signals can be well encoded at all possible stimulus intensities occurring under natural conditions. Our results demonstrate that the heterogeneity in the response properties of neuronal populations indeed improves the representation of sensory stimuli.
Keywords:
Electric Fish,
neuron models,
population heterogeneity,
sensory encoding
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Sensory processing and perception
Citation:
Walz
H,
Grewe
J and
Benda
J
(2012). Heterogeneity improves the encoding of natural stimuli in a neuronal population.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00234
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Received:
09 May 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Miss. Henriette Walz, Ludwig-Maximilians-Universität München, München, Germany, walz@bio.lmu.de