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Model for a robust neural integrator

Abstract

Integrator circuits in the brain show persistent firing that reflects the sum of previous excitatory and inhibitory inputs from external sources. Integrator circuits have been implicated in parametric working memory, decision making and motor control. Previous work has shown that stable integrator function can be achieved by an excitatory recurrent neural circuit, provided synaptic strengths are tuned with extreme precision (better than 1% accuracy). Here we show that integrator circuits can function without fine tuning if the neuronal units have bistable properties. Two specific mechanisms of bistability are analyzed, one based on local recurrent excitation, and the other on the voltage-dependence of the NMDA (N-methyl-D-aspartate) channel. Neither circuit requires fine tuning to perform robust integration, and the latter actually exploits the variability of neuronal conductances.

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Figure 1: The oculomotor system as an example of an integrator.
Figure 2: The fine-tuning hypothesis.
Figure 3: Qualitative explanation of the new model containing bistable units.
Figure 4: Multistability in circuits with hysteretic units.
Figure 5: Robust integrator network using circuit-based bistability.
Figure 6: Response to weak inputs.
Figure 7: Integrator network based on the voltage-dependence of the NMDA conductance.
Figure 8: Robust integrator function when conductances are randomly chosen.

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Acknowledgements

The authors are grateful to C. Kaneko and H. Sompolinsky for encouragement and to S. Seung and his group for numerous helpful suggestions. A.A.K. and A. K. were supported by fellowships from the Swartz and Alfred P. Sloan Foundations. We also acknowledge grants NIH 461434 and NSF 450578.

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Correspondence to Alexei A. Koulakov.

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Koulakov, A., Raghavachari, S., Kepecs, A. et al. Model for a robust neural integrator. Nat Neurosci 5, 775–782 (2002). https://doi.org/10.1038/nn893

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