Flexible population coding of odors in the olfactory bulb: A biologically plausible multi-odor spiking network model with e-prop

Abstract

Understanding the neural mechanisms underlying odor representation and memory in the olfactory bulb (OB) is essential for advancing our knowledge of sensory processing and plasticity. Based on in vivo findings [1,2], we implemented and trained a recurrent spiking neural network (SNN) model with eligibility propagation (e-prop) plasticity [3,4]. The model supports both a binary (two-odor) and a biologically more realistic n-odor discrimination paradigm, allowing direct comparison between simplified and complex olfactory representations.

Our model architecture incorporates both regular and adaptive leaky integrate-and-fire neurons, and allows simulation of cholinergic and GABAergic modulation as observed experimentally. By presenting the network with multiple odor cues, we can explore capacity, generalization, and interference phenomena reminiscent of real olfactory circuits. The model reproduces distinct, odor-specific activation patterns in simulated neuronal populations and captures modulatory effects of cholinergic and GABAergic inputs, in line with experimental observations.

Extending the analysis from single neurons to population activity, we investigate the structure and dimensionality of responses evoked by multiple odors within the network. Our analyses reveal that the network’s responses to different odors are organized along low-dimensional manifolds, reflecting the underlying coding capacity and flexibility of the olfactory bulb. Together, these results establish a biologically plausible framework for flexible, low-dimensional odor population codes in the olfactory bulb.

References

[1] Inna Schwarz and Monika Müller, Irina Pavlova, Jens Schweihoff, Fabrizio Musacchio, Manuel Mittag, Martin Fuhrmann, Martin K. Schwarz, The diagonal band of Broca regulates olfactory-mediated behaviors by modulating odor-evoked responses within the olfactory bulb, 2021, bioRxiv 2020.11.07.372649, doi: 10.1101/2020.11.07.372649ꜛ
[2] Monika Müller, Odor-evoked modulation of the olfactory bulb by projections from the horizontal limb of the diagonal band of Broca, Bonn, 2021, Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn. Online-Ausgabe in bonndoc: nbn-resolving.org/urn:nbn:\de:hbz:5-63028ꜛ
[3] Marc-Oliver Gewaltig and Markus Diesmann, NEST (NEural Simulation Tool), 2007 Scholarpedia, 2(4), 1430, doi: 10.4249/scholarpedia.1430ꜛ
[4] Guillaume Bellec, Franz Scherr, Anand Subramoney, Elias Hajek, Darjan Salaj, Robert Legenstein, Wolfgang Maass, A solution to the learning dilemma for recurrent networks of spiking neurons, 2020, Nature Communications, Vol. 11, Issue 1, pages n/a, doi: 10.1038/s41467-020-17236-yꜛ