# Unraveling Hydra bioelectrical activity on multielectrode array

## TL;DR

This study shows how Hydra vulgaris can be used with multielectrode arrays to record bioelectrical activity, offering new opportunities for bioelectronics research.

## Contribution

The study introduces a method for whole-organism bioelectrical recordings using Hydra and a custom MATLAB algorithm for signal analysis.

## Key findings

- Two recording configurations showed different bioelectrical patterns based on tissue-electrode coupling.
- Hydra's bioelectrical activity is highly dependent on the device architecture used.
- Hydra is proposed as a versatile model for bioelectronics and neuronal studies.

## Abstract

Introduction: Multielectrode array (MEA) technology has emerged as a powerful tool for extracellular recording of electrical activity across a wide range of experimental models, from single cells to organoids. Advanced devices have been developed to monitor and stimulate microscale biological systems enabling precise interrogation of cellular networks and tissue-level electrophysiology. Although these technologies generated promising results, they are not yet widely accessible to neuroscientists and neurobiologists due to limitations in adapting MEAs for whole-organism recordings, in maintaining stable tissue-electrode interfaces, and in decoding the complexity and diversity of bioelectrical signals of intact organisms.

Methods: In this study, we demonstrate the feasibility of recording the bioelectrical activity from a whole millimeter-sized organism (Hydra vulgaris) using a commercially available multielectrode recording system. Additionally, we introduce a custom MATLAB-based algorithm designed for comprehensive analysis and comparison of small animal model extracellular signals.

Results: Two distinct recording configurations were evaluated, each differing in the extent of tissue-electrode coupling area and resulting in variations of the recorded bioelectrical pattern.

Discussion: Our findings underline the strict dependency of the recordings from the device architecture and highlight the potential of Hydra as a versatile model in bioelectronics, with applications ranging from the development and validation of advanced microengineered devices to fundamental studies on neuronal circuits and neuromodulation.