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Limits to the temporal fidelity of cortical spike rate signals

Nature Neuroscience volume 5, pages 463–471 (2002)Cite this article

Abstract

The cerebral cortex processes information primarily through changes in the spike rates of neurons within local ensembles. To evaluate how reliably the average spike rate of a group of cortical neurons can represent a time-varying signal, we simulated an ensemble with realistic spike discharge behavior. We found that weak interneuronal correlation, or synchrony, allows the variability in spike rates of individual neurons to compromise the ensemble representation of time-varying signals. Brief cycles of sinusoidal modulation at frequencies above 115 Hz could not be represented by an ensemble of hundreds of neurons whose interneuronal correlation mimics that of the visual cortex. The spike variability and correlation assumed in our simulations are likely to apply to many areas of cortex and therefore may constrain the fidelity of neural computations underlying higher brain function.

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Figure 1: Model neurons mimic the variability and correlation of neurons in cortex.
Figure 2: Correlation causes fluctuations in the ensemble representation of a signal with a constant spike rate.
Figure 3: Random fluctuations in the ensemble spike rate can mimic a time-varying signal.
Figure 4: Correlation-induced fluctuations limit the temporal fidelity of the ensemble spike rate.
Figure 5: Ensemble fidelity is affected by firing rate dynamic range and signal width.
Figure 6: Ensemble fidelity depends on the time scale and magnitude of correlation.

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Acknowledgements

Supported by HHMI, NIH grants RR00166 and EY11378 and the McKnight Foundation. M.E.M. was supported by an NIH training grant (GM07108), a Poncin grant and an ARCS fellowship. We thank C. Brody, J. Ditterich, J. Gold, M. Leon and M. McKinley for comments and discussion.

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Authors and Affiliations

  1. Department of Physiology and Biophysics, Howard Hughes Medical Institute, Regional Primate Research Center, University of Washington, Box 357290, Seattle, 98195-7290, Washington, USA

    Mark E. Mazurek & Michael N. Shadlen

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Correspondence to Michael N. Shadlen.

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Mazurek, M., Shadlen, M. Limits to the temporal fidelity of cortical spike rate signals. Nat Neurosci 5, 463–471 (2002). https://doi.org/10.1038/nn836

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