Traditional lap pools are about 10 feet wide, though widths between 8 and 10 feet are common. (In competition pools, swim lanes are 2.5 meters wide, or about 8.2 feet.) You don't want to go too narrow with a lap pool.
The number of neurons in the brain varies dramatically from species to species. One estimate (published in 1988) puts the human brain at about 100 billion (10 11) neurons and 100 trillion (10 14) synapses.
Salem Press, 1998: 221.It has been estimated that the adult brain has around one hundred billion neurons and an even larger number of glial cells.100 billionThe Science Times Book of the brain. New York: The Lyons Press, 1987: 150.The human brain holds about 100 billion nerve cells.100 billionThe Scientific American Book of the Brain.