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.
Neurons within the neocortex are arranged vertically within neocortical columns. In the human brain, the neocortex has 500,000 of these particular columns and each column is in turn comprised of 60,000 neurons.