# Regulation of Synaptic Plasticity and Adaptive Convergence Under Rhythmic Stimulation of an In Vitro Hippocampal Neuronal Network of Cultured Cells

## TL;DR

This study explores how rhythmic electrical stimulation affects plasticity and adaptation in cultured hippocampal neurons, revealing how these networks can be modulated for learning.

## Contribution

The study identifies adaptive regulatory mechanisms in in vitro neuronal networks under rhythmic stimulation, revealing frequency-dependent plasticity modulation.

## Key findings

- Rhythmic stimulation (θ and γ) induces frequency-dependent plasticity modulation in cultured hippocampal networks.
- Adaptive convergence is observed as the difference in modulation effects between rhythms diminishes with repeated stimulation.
- The findings provide a technical foundation for shaping and modulating in vitro neural networks.

## Abstract

Synaptic plasticity constitutes a fundamental mechanism of neural systems. Rhythmic activities (e.g., θ and γ oscillations) play a critical role in modulating network plasticity efficiency in biological neural systems. However, the rules governing plasticity and adaptive regulation of in vitro cultured networks under structured electrical stimulation remain insufficiently characterized. To quantitatively investigate these regulatory effects within a highly controlled and low-interference environment, we utilized primary mice hippocampal neurons cultured on multielectrode arrays (MEAs) and executed two dedicated sets of experiments. (1) Spatiotemporal electrical stimulation paradigms, combined with connectivity analysis, revealed pronounced regulation effects of network plasticity. (2) Physiologically inspired rhythmic stimulation (θ: 7.8 Hz, γ: 40 Hz) with varying pulse repetitions was then applied. Although both rhythms induced distinct frequency-dependent plasticity modulation, the disparity between their modulatory effects progressively diminished with increasing stimulation pulse numbers, suggesting an intrinsic adaptive regulatory mechanism. Collectively, our findings characterize the effects of plasticity regulation and reveal the mechanisms underlying adaptive convergence in in vitro neuronal systems. These results advance the understanding of network plasticity, providing a technical foundation for functional shaping and modulation of in vitro neural networks while supporting future explorations into learning-oriented modulation.