Interleukin 1 also plays a role in the central nervous system. Research indicates that mice with a genetic deletion of the type I IL-1 receptor display markedly impaired hippocampal-dependent memory functioning and long-term potentiation, although memories that do not depend on the integrity of the hippocampus seem to be spared. However, when mice with this genetic deletion have wild-type neural precursor cells injected into their hippocampus and these cells are allowed to mature into astrocytes containing the interleukin-1 receptors, the mice exhibit normal hippocampal-dependent memory function, and partial restoration of long-term potentiation.