Cell type specific astrocytic feedback regulates excitation inhibition balance and cortical network dynamics

A recent study delves into the intricate role of astrocytes in regulating cortical network dynamics. Astrocytes, once thought to simply passively support neurons, are now known to actively modulate synaptic transmission and neuronal excitability. However, their influence on macroscopic cortical network regimes and slow-wave oscillations has been an area of ongoing research.

To explore this further, the researchers employed a computational network model that interconnected excitatory and inhibitory neurons with astrocytes. This model allowed them to observe how the bidirectional interactions between neurons and astrocytes shape overall network behavior.

The key finding was that it was not the strength of astrocytic coupling that determined network dynamics, but rather the topology of the feedback loops. By examining different pathway-specific connections, the team discovered that both the population of neurons driving astrocytic activation and the population receiving gliotransmission played crucial roles in determining whether the network operated in asynchronous irregular (AI), synchronous irregular (SI), synchronous regular (SR), asynchronous regular (AR), or quiescent regimes.

Notably, directing gliotransmission solely onto excitatory neurons consistently led to population synchrony, irrespective of which population was influencing astrocytic dynamics. Conversely, selectively targeting inhibitory interneurons resulted in network quiescence through strong suppression.

The researchers also found that when gliotransmission was directed to both excitatory and inhibitory neurons simultaneously, the network's synchrony status depended on which population was driving astrocytic dynamics. If excitatory neurons were the primary drivers, the network exhibited synchrony; if excitatory and inhibitory populations collaborated or inhibitory neurons alone held sway, the network remained asynchronous.

Moreover, the study uncovered that the kinetics of astrocytic signaling provided an additional temporal control mechanism. This regulation influenced the frequency and persistence of self-sustained up states within the cortical network.