Scientists watch how mice learn, one synapse at a time

One of the brain's most important properties is its flexibility. Our cerebral circuitry changes constantly--every day, new links are made amongst the 86 billion individual neurons in our heads, and old connections are allowed to fall away. The result is a dizzyingly complicated network that is in a constant state of flux, rewiring itself on the fly in response to its environment and the life experience of its owner. The brain's ability to do this is called neuroplasticity, and it's what gives us the capacity to learn, grow, develop new skills and ideas, and adapt to the environment in which we live. We understand some aspects of neuroplasticity fairly well but others, including the reason that certain connections get made instead of others, remain deeply mysterious.