Some interesting news from the field of aging and the loss of speed and fine motor control in seniors. Seems the problem is due to a loss of myelin in key motor neurons leading to declining signal conductance along those pathways. Myelin is the insulating sheath of fat that surrounds neuronal axons, and a new report suggests that even healthy people begin to lose some of that insulation in motor neurons at age forty. The loss of myelin along those motor pathways corresponds directly to the loss of speed in movement and reflexes. Myelin production also goes into decline in the cognitive pathways about a decade later, signaling a slow down in other mental processes as well.
You can read the article at Time.com for the research and more information on myelin, but it goes to show that signal conductance along the nerve is just as important to consciousness as neural connectivity.