In this paper, we investigated why different cellular signaling pathways in astrocytes (a type of glial cell in the brain) have different effects on the storage of recent and remote memories. We found that astrocytes do so by modulating the same mechanism: namely, the recruitment of neurons that connect two brain regions (the CA1 of hippocampus and the ACC) to the general group of neurons that store the memory. One signaling pathway, called Gq, enhances the recall of recent memories and the early recruitment of the hippocampus to the cortex-connecting neurons. Another pathway, called Gi, impairs the recall of remote memories and the late recruitment of the hippocampus to the same  cortex-connecting neurons.

Figure 1: Astrocytes, recent and remote memory engrams in the mouse hippocampus.

Figure 2: Axons leaving the hippocampus and traveling toward the ACC.