" The great Spanish neuroanatomist Santiago Ramon y Cajal concluded his 1913 treatise “Degeneration and Regeneration of the Nervous System” with this declaration: “In adult centres the nerve paths are something fixed, ended, immutable. Everything may die, nothing may be regenerated.” Cajal based his pessimistic conclusion on his meticulous studies of brain anatomy after injury, and his gloomy sentiment remained neuroscience dogma for almost a century. “We are still taught that the fully mature brain lacks the intrinsic mechanisms needed to replenish neurons and reestablish neuronal networks after acute injury or in response to the insidious loss of neurons seen in neurodegenerative diseases,” noted the neurologists Daniel Lowenstein and Jack Parent in 1999. "

― Jeffrey M. Schwartz , The Mind and the Brain: Neuroplasticity and the Power of Mental Force