# Emergent functions of noise-driven spontaneous activity: homeostatic maintenance of criticality and memory consolidation

## TL;DR

The brain uses random activity to maintain optimal function and memory, even when resting, which could help design better neural networks.

## Contribution

Noise-driven spontaneous activity is shown to maintain criticality and aid memory consolidation in neural systems.

## Key findings

- Spontaneous activity helps restore criticality and EI balance after disruptions.
- Noise and STDP stabilize neural network properties and prolong memory of past stimuli.
- The findings suggest a link between spontaneous activity and sleep's role in memory.

## Abstract

Unlike digital computers, the brain exhibits spontaneous activity even during complete rest, despite the evolutionary pressure for energy efficiency. Inspired by the critical brain hypothesis, which proposes that the brain operates optimally near a critical point of phase transition in the dynamics of neural networks to improve computational efficiency, we postulate that spontaneous activity plays a homeostatic role in the development and maintenance of criticality. Criticality in the brain is associated with the balance between excitatory and inhibitory synaptic inputs (EI balance), which is essential for maintaining neural computation performance. Here, we hypothesize that both criticality and EI balance are stabilized by appropriate noise levels and spike-timing-dependent plasticity (STDP) windows. Using spiking neural network (SNN) simulations and in vitro experiments with dissociated neuronal cultures, we demonstrated that while repetitive stimuli transiently disrupt both criticality and EI balance, spontaneous activity can develop and maintain these properties and prolong the fading memory of past stimuli. Our findings suggest that the brain may achieve self-optimization and memory consolidation as emergent functions of noise-driven spontaneous activity. This noise-harnessing mechanism provides insights for designing energy-efficient neural networks, and suggest a potential link between the emergent function of spontaneous activity and sleep function in maintaining homeostasis and consolidating memory.