Astrocyte-Mediated Higher-Order Control of Synaptic Plasticity

TL;DR

This paper introduces a higher-order model of tripartite synapses incorporating astrocyte interactions, demonstrating how astrocytes stabilize circuit dynamics and improve stimulus processing in recurrent neural circuits.

Contribution

It presents a novel higher-order model of astrocyte-mediated synaptic plasticity, exploring its effects on circuit stability and information processing.

Findings

Higher-order astrocyte interactions stabilize recurrent circuit dynamics.

Astrocyte modulation expands the parameter space for stimulus-driven activity.

The model generalizes previous short-term plasticity models to include astrocyte effects.

Abstract

The dynamics of higher-order topological signals are increasingly recognized as a key aspect of the activity of complex systems. A paradigmatic example are synaptic dynamics: synaptic efficacy changes over time driven by different mechanisms. Beyond traditional node-driven short-term plasticity mechanisms, the role of astrocyte modulation through higher-order interactions, in the so-called tripartite synapse, is increasingly recognized. However, the competition and interplay between node-driven and higher-order mechanisms have yet to be considered. Here, we introduce a simple higher-order model of the tripartite synapse accounting for astrocyte-synapse-neuron interactions in short-term plasticity. In the model, astrocyte gliotransmission and pre-synaptic intrinsic facilitation mechanisms jointly modulate the probability of neurotransmitter release at the synapse, generalizing previous short-term plasticity models. We investigate the implications of such mechanisms in a minimal recurrent motif -- a directed ring of three excitatory leaky integrate-and-fire neurons -- where one neuron receives external stimulation that propagates through the circuit. Due to its strong recurrence, the circuit is highly prone to self-sustained activity, which can make it insensitive to external input. By introducing higher-order interactions among different synapses through astrocyte modulation, we show that higher-order modulation robustly stabilizes circuit dynamics and expands the parameter space that supports stimulus-driven activity. Our findings highlight a plausible mechanism by which astrocytes can reshape effective connectivity and enhance information processing through higher-order structural interactions -- even in the simplest recurrent circuits.