Many neuroscientists are empiricists: together, with the English Enlightenment philosopher John Locke (1632–1704), they presume that the brain simply draws its

To cement the event, the neurons that were recently activated undergo major physical changes. They modify the strength of their interconnections, thus increasing the group support and making it more likely that this set of neurons will fire in the future. Some synapses become physically larger and may even get duplicated.

Just a few weeks of stress causes neurons, particularly neurons in the hippocampus (Illustration 4), a part of the brain involved in memory and learning, to begin to wither and die.