The molecular mechanisms that enable memories to persist over long timescales from days to weeks and months are still poorly understood1. Here, to develop insights into this process, we created a behavioural task in which mice formed multiple memories but only consolidated some, while forgetting others, over the span of weeks. We then monitored circuit-specific molecular programs that diverged between consolidated and forgotten memories. We identified multiple distinct waves of transcription, that is, cellular macrostates, in the thalamocortical circuit that defined memory persistence.
Astrocytes - brain cells once thought of as supporting players to neurons - have a principal role in stabilizing memories for long-term recall. In mice, researchers found that Fos, a gene associated with cell activity, was highly expressed in the astrocytes of mice that re-entered cages they'd been conditioned to associate with fear. The team also found that highly-active astrocytes produce more receptors that respond to the neurotransmitter noradrenaline, which allows them to communicate with neurons.