In addition to the enigmatic nature of the brain and the various observations that are made about it, an additional issue obscuring our ability to develop a clear picture is that there are so many differing ideas about what meditation is or isn’t.
First, and most importantly, different kinds of meditation affect the brain very differently. For example, a recent study of Buddhist monks in meditation showed widespread gamma wave activity distributed all over the brain along with several other changes. Yet a study of people using a mindfulness form of meditation showed alpha activity, at the opposite end of the spectrum to gamma, which was more prominent in the left frontal side of the brain compared to the right. Two related kinds of meditation yield electrical activity at opposite ends of the spectrum and in completely different patterns of distribution. Another form of meditation has been shown to generate electrical changes that resemble sleep. So It seems logical that if different parts of the brain are activated, then this is highly likely to have different effects. Short term studies are unlikely to show what those different effects might be. Our assessment of the entire meditation research literature, described in chapter XX, found that the average observation period for a meditation study is only 2 to 3 months. Yet meditation was itself originally intended to be a lifelong practice. The problem is we do not have enough of that kind of long term information see whether or not these differences in brain activity might end up generating practical differences in terms of health, wellbeing or functionality. Is one pattern of activation better than another? Might one be more useful in certain circumstances compared to another? These questions have yet to be answered, regardless of what you may read in the media. It would seem that it certainly disproves a rather popular idea that all forms of meditation are the same. All roads do not lead to Rome, the brain science seems to say.
Second, the question of specific effect again raises its head, possibly even more so than before. This is because while various meditation techniques have been shown to involve certain parts of the brain and certain patterns of activity similar changes have often been observed in non-meditative activities as well. For example, when a person does a meditation technique that involves focused attention there will be activation of those parts of the brain that allow us to focus our attention. In fact most researchers will agree that the one thing that appears to be common to all meditation techniques is the activation of a region of the brain in the limbic system, called the anterior cingulate gyrus. This brain centre is responsible for the focusing of attention which seems logical since most meditation techniques involve some kind of manipulation of attention. However when we read a book or do a mathematical calculation we also activate the same areas of the brain because we need to focus our attention for those tasks to be done as well. Focused attention alone is not an adequate definition of meditation. Similarly, while meditation techniques involves parts of the brain that govern relaxation of the body, so to do non-meditative activities such as sitting under a tree in the park. What aspect of meditation, and its resulting impact on the brain, is truly specific to meditation and not other things? We can’t answer this question, I feel, until we come up with a specific and consistent definition of meditation. Again, the value of using mental silence as the definition of meditation seems obvious in this situation.
Third, there is currently no uniformity in the way that studies have been conducted. Some have been quite poorly designed despite the pretty pictures and hence the results are not very reliable whereas a small number have been designed and conducted very well. Yet even the well designed ones don’t allow for good cross comparison. Add to this the wide differences between different meditation techniques and it becomes obvious that instead of a broad and comprehensive picture we have small islands of good evidence surrounded by oceans of unclear data. The challenge in getting meaning out of the brain sciences is now no longer about the technology, for that clearly exists, so much as the need to get a clear understanding of what meditation really is. That’s why we feel that the mental silence definition is of such potential use.
In the studies described in the book the patterns of activation observed in association with sahaja yoga have been symmetrical rather than asymmetrical, involving the front and midline areas of the surface of the brain. It’s thought that these surface changes are reflective of activation of deeper structures inside the brain, particularly the anterior cingulate gyrus and other structures involved in focused attention and mood. The fact that other studies of non-mental silence meditation have not shown the same patterns in combination with the fact that the strength of these changes seems to correlate very closely with the degree of mental silence that the meditator reports suggest that these might be the changes crucial and specific to the mental silence experience.