Scientists at the Hospital for Sick Children in Toronto have discovered that microglia — the brain's immune cells — play a direct role in helping the brain unlearn fear. During extinction learning (the process by which fear memories fade), microglia physically interact with fear-encoding neurons in the hippocampus. They temporarily silence these neurons by contacting their cell bodies, and separately trigger the pruning of synapses by contacting their branches. Blocking either process slowed fear extinction in mice. This challenges the long-held view that fear memory erasure is purely a neuronal process and positions microglia as active architects of memory remodeling. The findings could reshape how we approach PTSD and anxiety disorder treatments.
