Neuroplasticity by Moheb Costandi

Author:Moheb Costandi
Language: eng
Format: mobi, epub
Publisher: The MIT Press
Published: 2016-08-11T00:00:00+00:00

Of Mice and Men

Neuroimaging studies have provided a wealth of information about how prolonged intensive mental training alters the brain, but they tell us nothing about the molecular and cellular mechanisms underlying the observed changes. Experiments performed on rodents show that rigorous training on motor tasks can exert various cellular effects, such as the sprouting and pruning of new dendritic spines and axonal branches. It is impossible to observe equivalent processes in humans, however, both because the resolution of current neuroimaging technologies is far below that needed to visualize them and because the techniques used in mice and rats cannot be applied to studying the human brain.

Increases in gray matter density and volume could be explained by adult neurogenesis. That explanation is particularly attractive in the case of London taxi drivers, since the hippocampus is currently the only region of the human brain that is known to continue generating new neurons throughout life (see chapter 5). But the increases can also be explained by the formation of new dendritic spines and synapses and the sprouting of new axon branches. Increases in the number of glial cells, or the formation of new blood vessels to supply new structures with blood, could also increase gray matter density.

Likewise, changes in white matter structure could be due to various mechanisms, such as the addition and removal of myelin from axons, or alterations in myelin thickness or in the spacing between nodes of Ranvier, all of which would alter the conducting properties of a neuron. Although diffusion tensor imaging is sensitive to variations in myelin, it is not yet sensitive enough to distinguish between these mechanisms.18

Neuroimaging data can sometimes seem counterintuitive and are often difficult to interpret. One recent study compared brain activity of professional soccer players and swimmers while they performed identical foot movements, and found that the soccer players exhibited less activity in the motor cortical area corresponding to the foot than did the swimmers. The researchers interpreted this as meaning that years of training enable the soccer players to control their foot movements efficiently while also conserving their neural resources.19

Clearly, the brain is highly flexible, but we are only just beginning to understand the many ways in which it can adapt to the demands placed upon it. Technological advances will allow for increasingly sophisticated ways of imaging the brain, and will surely deepen our knowledge of how different types of training affect brain structure and function.

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