Final answer:
Santiago Ramón y Cajal proposed the neuron doctrine which incorrectly stated that neurons do not regenerate. However, contemporary research has revealed the occurrence of limited neurogenesis in adults, refuting the complete accuracy of the neuron doctrine.
Step-by-step explanation:
Santiago Ramón y Cajal, a Nobel Prize laureate, is known for proposing the neuron doctrine. This doctrine, earlier believed to be a complete explanation of neuronal regeneration, incorrectly stated that neurons do not regenerate. Ramón y Cajal's work was revolutionary in the understanding of the nervous system, where he reported structures in neurons and drew detailed micrographs of brain nerve cells. Contemporary science has shown, however, that this view of neuronal regeneration is not entirely accurate.
There is now evidence of neurogenesis, the process of new neuron formation, occurring in the human brain even in adulthood, albeit at a limited capacity. This neurogenesis is facilitated by the division of undifferentiated neural stem cells. Fully differentiated neurons themselves cannot divide, meaning that the neuron doctrine was only partially correct in stating that mature neurons do not replicate in the way other body cells might.
Nevertheless, the number of new neurons generated in this way is not likely to replace significant amounts of brain neurons lost to injury or disease. Hence, while the neuron doctrine posited by Ramón y Cajal was pivotal for neuroscience, it slightly oversimplified the regeneration capabilities of neurons.