The 3-Body Problem: How Astrocytes May Govern Plasticity.

Learning and memory were long thought to be the domains of neurons and neural networks, but recent work across brain systems has established that astrocytes play a role in synaptic plasticity and information storage. However, it remains unclear what this role is. In Hebbian and spike timing-dependent plasticity, simultaneous activation of pre- and postsynaptic neurons on a millisecond timescale determines plasticity, yet emerging evidence suggests that slow astrocyte signaling over many seconds is directly linked to memory. Here we take an astrocyte-centric view on plasticity to explore the possible computational and coding roles of astrocytes. We propose that in a 3-body arrangement with pre- and postsynaptic compartments, astrocytes may participate in the synaptic credit assignment problem. This review thus offers a candidate conceptual framework for understanding the interplay between astrocytes and neurons in the context of neural network performance and plasticity.