From a discrete model of chemotaxis with volume-filling to a generalised Patlak-Keller-Segel model

TL;DR

This paper derives a generalized Patlak-Keller-Segel chemotaxis model from a discrete agent-based framework, incorporating volume-filling effects, and validates it through numerical comparisons in one and two dimensions.

Contribution

It introduces a discrete chemotaxis model with volume-filling effects and formally derives a generalized PKS model, demonstrating strong agreement with discrete simulations.

Findings

Quantitative agreement between discrete and continuum models.

Conditions for spatial pattern formation analyzed.

Model replicates classical PKS behavior asymptotically.

Abstract

We present a discrete model of chemotaxis whereby cells responding to a chemoattractant are seen as individual agents whose movement is described through a set of rules that result in a biased random walk. In order to take into account possible alterations in cellular motility observed at high cell densities (i.e. volume-filling), we let the probabilities of cell movement be modulated by a decaying function of the cell density. We formally show that a general form of the celebrated Patlak-Keller-Segel (PKS) model of chemotaxis can be formally derived as the appropriate continuum limit of this discrete model. The family of steady-state solutions of such a generalised PKS model are characterised and the conditions for the emergence of spatial patterns are studied via linear stability analysis. Moreover, we carry out a systematic quantitative comparison between numerical simulations of the discrete model and numerical solutions of the corresponding PKS model, both in one and in two spatial dimensions. The results obtained indicate that there is excellent quantitative agreement between the spatial patterns produced by the two models. Finally, we numerically show that the outcomes of the two models faithfully replicate those of the classical PKS model in a suitable asymptotic regime.