While learning activates key biological processes by which new memories can be formed, Yi Zhong , from Tsinghua University (China), and colleagues have identified  a chemical in the brain that deliberately removes short-term memories, to enhance the brain’s capacity to learn.   Using an insect model, the researchers elucidated the mechanisms underlying Rac, a protein. When Rac is blocked, the the brain retains information for far longer than it would normally.  But Rac is released at a faster rate when the brain is attempting to process large amounts of information, clearing more space as it is needed. Reporting that: “Endogenous Rac activation is evoked on different time scales during gradual memory loss in passive decay and during acute memory removal in reversal learning,” the researchers propose that: “Rac's role in actin cytoskeleton remodeling may contribute to memory erasure.”