2014 : WHAT SCIENTIFIC IDEA IS READY FOR RETIREMENT?

Brain plasticity refers to the fact that neurons are capable of changing their structural and functional properties with experience. That seems hardly surprising since every part of the body changes with age. What is special about brain plasticity (but not unique to this organ) is that the changes are mediated by specific events that are in some sense adaptive. The field of brain plasticity primarily derives from the pioneering studies of Torsten Wiesel and David Hubel who showed that depriving one eye of normal visual input during early development resulted in a loss of functional connections of that eye with the visual cortex, while the connections of the eye not deprived of visual input expanded.

These studies convincingly demonstrated that early brain connections are not hard-wired, but could be modified by early experience hence they were plastic. For this work, and related studies, done in the 1960's Wiesel and Hubel received the Nobel Prize in 1981. Since that time there have been thousands of studies showing a wide diversity of neuronal changes in virtually every region of the brain, ranging from molecular to the systems level, in young, adult and aged subjects. As a result, by the end of the 20th century our view of the brain evolved from the hard wired to the seemingly ever changeable. Today plasticity is one of the most commonly used words in the neuroscience literature. Indeed, I have employed this term many times in my own research articles and used it in the titles of some of my edited books. So what's wrong with that, you may ask?

For one thing, the widespread use of "brain plasticity" to virtually every type of change in neuronal structure and function has rendered this term largely meaningless. When virtually all and any change in neurons is characterized as plasticity, the term encompasses so much that it no longer conveys any useful information. It is also the case, that many studies invoke brain plasticity as the underlying cause of modified behavioral states without having any direct evidence for neuronal changes. Particularly egregious are the studies showing improvements in performance on some particular task with practice. The fact that practice improves performance has been noted before anything was known about the brain. Does it really add anything to invoke that improvements in function demonstrate a remarkable degree of brain plasticity. The word "remarkable" is often used to denote practice effects in seniors as if those old enough to receive social security are incapable of showing enhanced performance with training.

Studies of this type have lead to the launch of a growing brain training industry. Many of these programs are focused on the very young. Particularly popular in past years was the "Mozart effect" which led parents, who had no interest in classical music themselves, to play continuously pieces by Mozart to their infants. This movement seems to have abated, replaced by a plethora of games that are suppose to improve the brains of children of all ages. But the largest growth in the brain plasticity industry has focused on the aging brain. Given the concerns that most of us have about memory loss and decreasing cognitive abilities with age this is understandable. There are large profits to be made as evident by the number of companies that have proliferated in this sector in recent years.

There is of course nothing wrong with having children or seniors engage in activities that challenge their cognitive functions. In fact, there may be some genuine benefits in doing so. Certainly undergoing such training is preferable to watching television for many hours each day. It is also the case that any and all changes in performance reflect some underlying changes in the brain. How could it be otherwise, since the brain controls all behaviors? But as yet, we do not know what occurs in the brain when performance improves on a specific video game, nor do we understand how to make such changes long lasting and generalizable to diverse cognitive states.  Terming such efforts brain training or enhanced brain plasticity is often just hype intended to sell a product. This does not mean that the so-called brain exercises should be abandoned. They are unlikely to cause harm and may even do some good. But please refrain from invoking brain plasticity, remarkable or otherwise, to explain the resulting improvements.