They used a somewhat bizarre technique
in which two mice were sutured together
in such as way that they shared a circulatory system (known as parabiosis), and found old mice joined to their youthful counterparts showed changes
in gene activity
in a brain region called the hippocampus as well as
increased neural connections and enhanced «
synaptic plasticity» — a mechanism believed to underlie learning and memory
in which the
strength of neural connections change
in response to experience.