Intriguing research into the mechanisms of age-related mental decline is discussed at Betterhumans. Scientists have identified a very low-level process in neurons that can be tweaked to at least partially negate "the cognitive decline that affects about 40% of people over 65. Although scientists don't know the exact cause of age-related mental decline, studies have implicated decreases in neuronal excitability as well as decreases in synaptic plasticity - basically, the ability of brain cells to change connections. ... the ion channel-altered mice retained neuronal excitability into old age and had greater synaptic plasticity." This is early stage work, of course, but - like all research on the brain - very important to the big picture of regenerative medicine.