Recently, after I had pointed out that parts of the brain differ in their plasticity (ability to be shaped by environmental stimulation), a reader asked me about programs like "Brain Fitness", which claim to be able to change the brain. People writing about "Brain Fitness" and similar programs often use the concept of plasticity to argue that it should be possible to stimulate the brain in ways that will actually alter it.
Is there any truth to this claim? On the whole, I have to say that it is questionable-- the kind of statement that some logicians call "confident speculation". Paradoxical though it may seem, while there is good science BEHIND many of these programs, there is little good science ABOUT them. The programs are based on serious research into brain structures and functions, but that can only provide a beginning. What is needed is a set of good outcome studies showing whether or not the programs are effective. As I commented the other day in a post about "evidence-based treatment", one requirement is that there be some independent replications of studies, done by individuals who do not have as much commitment to the program as the original researchers did. This is unlikely to happen when the programs are "proprietary" programs whose details are not readily available to the public and whose research evidence is not published in professional journals. In these frequent cases, we, the public, depend for evidence on the owners of the program, and it does not take an advanced case of cynicism to think that they may be less than transparent in their presentation.
Let me take an example of this problem that is related to "Brain Fitness" (which, by the way, may be perfectly harmless and even be shown in the future to be effective). An article entitiled "Brain plasticity and functional losses in the aged" (Mahnke, Bronstone, & Merzenich, Progress in Brain Research, 2006, Vol. 157, pp. 81-109) described a study in which elderly people were randomly assigned (good thing!) to groups, and one group received training on sensory, cognitive, and motor activities. The trained group then showed significantly better performance on a standardized memory test than the people who had not received the same training. All well and good-- but the title says "brain plasticity", and the article's conclusion attributed the change to brain plasticity. How do we then understand the fact that there was no independent measure of brain plasticity, the only relevant measure being the memory test? Why did the authors not call the article "Guided practice and functional losses in the aged"? Why did they not simply conclude that a program that helps elderly people do some interesting, stimulating things seems to have at least one good cognitive effect? The answer I would suggest is that statements about the brain are currently "sexy" and inflate the importance of otherwise simple conclusions. (By the way, a very interesting discussion of this is in an article by D.S. Weisberg, "Media watch: The presentation of neuroscience information to the popular media", Scientific Review of Mental Health Practice, 2008, Vol. 6, pp. 51-56.)
I think it may help the discussion to introduce a couple of concepts about brain plasticity. Such guidance of development by the environment can occur in two major ways. One, which includes the visual cortex functions I mentioned yesterday, is called "experience-expectant plasticity". This type of plasticity involves a fine-tuning of functions by the environment, during a particular period in development, and under circumstances that almost all members of a species will undergo. This form of plasticity results in brain changes that can be measured in animals, but as they require autopsy and sometimes other treatments while the animal is alive, these are not done on human beings. Although we do not know for sure that these changes occur in humans, we do at least have an idea of what kinds of changes we are talking about, and we have a reasonably good idea that once these changes are finished, they cannot be reversed.
The other type of brain plasticity is called "experience-dependent plasticity". It involves the still poorly-defined changes (in the whole brain, in circuits, or in individual neurons) that are at work in learning. Such plasticity-- as evidenced in learning-can take place throughout the lifespan. It can be reversed if new experiences occur. However, there is no way at this point to measure the relevant changes in the brain. When we see that learning has occurred, we assume that it indicates brain plasticity at work, because we do not at this point in history accept any other explanation (nor do I want to imply that I think there is an alternative).
To my mind, the problem with making the logical jump from improved memory to "brain plasticity" is that the audience is likely to equate the two. Add to this the confusion about the two types of plasticity, and we end with the mistaken conclusion that all forms of brain development can be altered or reversed by the application of environmental stimulation. We would be far better off to think about "behavioral plasticity" or "cognitive plasticity" and to ask for evidence of measurable change resulting from proprietary programs, rather than allowing ourselves to be blinded with what appears to be science.
