# Modeling spontaneous activity across an excitable epithelium: Support for a coordination scenario of early neural evolution

## TL;DR

The paper explores how early nervous systems may have evolved by modeling how excitable epithelia can coordinate activity across a body.

## Contribution

A computational model is introduced to test the coordination capabilities of excitable epithelia as a potential precursor to nervous systems.

## Key findings

- Excitable epithelia can spontaneously generate body-scale activation patterns.
- Coordination emerges in smaller bodies with cellular excitability and bidirectional signaling.
- Noise level, body dimensions, and size influence the extent of coordination.

## Abstract

Internal coordination models hold that early nervous systems evolved in the first place to coordinate internal activity at a multicellular level, most notably the use of multicellular contractility as an effector for motility. A recent example of such a model, the skin brain thesis, suggests that excitable epithelia using chemical signaling are a potential candidate as a nervous system precursor. We developed a computational model and a measure for whole body coordination to investigate the coordinative properties of such excitable epithelia. Using this measure we show that excitable epithelia can spontaneously exhibit body-scale patterns of activation. Relevant factors determining the extent of patterning are the noise level for exocytosis, relative body dimensions, and body size. In smaller bodies whole-body coordination emerges from cellular excitability and bidirectional excitatory transmission alone. Our results show that basic internal coordination as proposed by the skin brain thesis could have arisen in this potential nervous system precursor, supporting that this configuration may have played a role as a proto-neural system and requires further investigation.