A study published in PLoS Biology has identified two separate physical processes that occur in the brain during learning, operating at different speeds and in different cell types.
Using advanced imaging in mice trained on a skilled reaching task, researchers tracked structural changes in the primary motor cortex over hours and days.
Within the first hour of training, astrocytes — support cells that regulate the brain's chemical environment — showed significant swelling around active synapses.
This rapid astrocytic response was temporary, returning to baseline within 24 hours, and appeared linked to increased local blood flow and neurotransmitter clearance.
In contrast, structural growth in neurons, specifically the formation of new dendritic spines on pyramidal cells, began later and persisted for weeks.
The spine growth correlated with long-term retention of the learned skill, suggesting it underlies durable memory storage.
The authors note that most previous studies have focused on neuronal changes alone, potentially overlooking the early astrocyte response.
They suggest the two-phase mechanism may reflect an initial protective or supportive role for astrocytes before permanent circuit rewiring occurs.
Learning a new skill triggers both temporary cell swelling and lasting brain growth
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