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The long journey of neuroplasticity

Did you know that the mind can change brain’s structures and functions and that new neurons can grow after birth? Although today these are well accepted facts by the scientific community, this has not always been the case! It took a hundred years for a considerable paradigm shift to occur, from the initial view of a hard wired brain, in other words a brain that stays the same after it is formed, to that of a neuroplastic brain which has the ability to change its structure and functioning through experiences and the conscious use of directed thoughts. For all this time scientists were convinced that:

the brain’s functions and structures could not change after birth.

The process of neurogenesis1, by which neurons are generated and therefore responsible for populating the brain, occurred only during prenatal development and that no new neurons could appear after birth.

In fact the brain was thought to be very different from other organs of the body because mature neurons do not divide whereas in most organs of the body instead, the major source of new cells comes from cellular division. Hence, the established view was that mammalian brain’s structures were set from birth and that no new neurons would grow during one’s lifetime. As it often happens in science, it took a lot of evidence to change this established dogma.

The first data showing that the brain was neuroplastic (see neuroplasticity2), was collected as early as 1923 when an experiment was done showing that animals’ movement maps could change. Was the data accepted? No, it was not ! The experiment was simply ignored because it was contrary to the accepted belief that animals’ differences in movement maps were genetic rather than based on experience.

More evidence pointing in the same direction was collected throughout the eighties when it was shown that the sensory systems of animals were not consisting of hard-wired machines. For instance, in 1982, two researchers working with an owl monkey collected the first evidence that cortical areas of the brain in a primate could remap. They showed that if one finger was denervated in a way that it would stop sending signals to the brain, that part of the cortex would be taken over by other fingers. Since, again, these results contradicted the established view of a hard-wired brain, they did not easily get their work published.

Yet more evidence was also collected in humans. However, despite the accumulation of data in favour of neuroplasticity, skepticism prevailed amongst peers until neurogenesis was itself proven, because it was difficult to accept neuroplasticity whilst at the same refusing neurogenesis : how could it be possible for the structure and function of the human brain to change if no new neurons could grow?

Fortunately, for neurogenesis too there was an accumulation of evidence up and through the 80’s until eventually, the quality of the data improved to the point that it was finally accepted and the model of a hard-wired brain rejected.

One of the key studies was done in Sweden on cancer patients. Its purpose was to spot cancer cells, hence patients were given a radioactive label called BRDU that marks the growth of new cells. Now in the 5 five terminally ill patients who had been enrolled, the BRDU labeled cells were found (after their deaths) in the part of the hippocampus called the dentate gyrus and it is now accepted that human brains make new neurons in the dentate gyrus of the hippocampus. The discovery was that neurons could develop from stem cells3 and that they could incorporate themselves into the functional architecture of the brain was very significant because it contradicted the view that the brain was so completely different from other organs in that no cellular (neuron) division occurred in it.

1Neurogenes: is the process by which neurons are generated and therefore responsible for populating the brain with neurons. It occurs mainly during prenatal development.

2 Neuroplasticity: the ability to change the structure and functioning of the brain through experiences and the conscious use of directed thoughts

3Stem cells: cells that are characterized by their capacity to renew themselves through cell division and give rise (differentiate) into a diverse range of specialized cell types. They are found in multi cellular organisms
Reference article: Begley, S. “Train Your Mind, Change Your Brain: How a New Science Reveals Our Extraordinary Potential to Transform Ourselves”.

By the Horizon Research Foundation editorial board

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