Frontal Lobes, the Limbic System, Meditation & Mental Silence
Now the brain science tells us that some of these components, particularly focused attention, relaxation and shift in mood, occur in most meditation methods and hence it is common to see those areas of the brain become activated during meditation regardless of which technique is being studied. However there is also research that shows that different techniques can often involve other areas of the brain in addition to those common areas. Furthermore, the way in which these areas become involved and interrelate with each other can also differ between techniques. This of course raises the question about which pattern of brain activity if good for us, bad for us or of no consequence. As of yet no single unified understanding has emerged that explains all the different approaches to meditation or their often different effects on the brain.
Parts and Patterns
The two important areas of the brain that feature prominently in meditation research are the frontal lobes, located in the area of the forehead, above the eyebrows and the limbic system which is deep inside the centre of the brain. Generally speaking, these two areas function and interact to influence our behavior, emotions, thinking, and what we’re going to do with our life. In other words together they have a profound influence on our personality, who we are and how we feel. The other parts of the brain are the parietal lobes, at the top of the head, which primarily deals with the physical body, the occipital lobes at the back of the head that deal mostly with vision and the temporal lobes, above the ears, which deal with auditory information.
The limbic system is, from an evolutionary point of view, an ancient structure that is found in both humans and lower animals, and is associated with survival instincts and emotions. The instinct to nurture our young, for example, or defend territory, are functions of the limbic system. The limbic system, and in fact emotion generally, has been studied by scientists with an inordinate interest in negative emotions such as fear, anger, anxiety and despair. However researchers have only recently come to acknowledge that equally if not more important are the positive emotions such as happiness and love since after all it is these emotions that we all aspire to achieve. The bias toward negative emotion is partly because the brain sciences emerged from the study of animals, mental illness (rather than mental wellness) and partly, I believe, because scientists seem to find it easier to identify negative feelings more commonly rather than positive ones. Whether or not this is a reflection of reality or a reflection of our culture is itself an important question.
Emotions originate from the limbic system but the nature of these emotions, either positive or negative, is strongly influenced by the frontal lobes which communicate with the limbic system through a set of important “fronto-limbic loops”.
The frontal lobes are more or less the “front portion” of the brain. The most important part of which is “the pre-frontal lobe”. The pre frontal lobes are considered to be the newest and hence most evolved part of the human brain. Only a few animals, dolphins are the best example, have a similar although more limited version of the structure. Our pre-frontal lobes appear to give us the ability to experience human happiness and enjoyment of life. They also seem to be responsible for other important positive human qualities such as idealism, joy, our ability to concentrate, creativity, and our ability to think abstractly. The frontal lobes and the limbic system work in tandem to influence our experience. To put it simply, the frontal lobes interpret situations and events and then communicate that interpretation through the “fronto-limbic loops” to the limbic system which then produces the appropriate emotion.
Many years ago early brain researchers identified specific places in the brain that dealt with specific functions. There is a specific area in the temporal lobes that deals with hearing and speech, for example, and another area in the parietal lobes that deals with physical sensations which are mapped out in the same part of the brain in every person. Extrapolating from that scientists proposed that there might be a single centre of the brain that deals with each aspect of our lives, our personality, mind and even consciousness itself. However the understanding that is now emerging is that while there are certainly centres that deal with the basic functions, more complex functions occur as a result of combining these different centres into a functional unit, or even parallel units, that work together to create a seemless experience. This does not necessarily relate to a single area of the brain so much as an intercommunicating network that combines the function of different areas in different ways.
Another important development is that scientists are coming to realize that the cortex of the brain, the “gray matter”, which is only about 3 millimitres thick and constitutes a small percentage of the total brain is not the only place where complex and important functions occur. There is now evidence emerging for the importance of areas deep inside the brain, “subcortical structures” or “white matter” such as the limbic system. So when your teacher told you to “use your grey matter”, you can rest assured that the statement was based on the mistaken assumption that only the cortex was responsible for intelligence. You can now reply “the stuff under the grey matter is just as important!”.
What this tells us is that it is quite likely that meditation may not actually trigger the activation of a single brain area so much as a certain network, or multiple networks, of areas, both on the surface of the brain and deep inside it, which then work together to produce the experience of meditation and its behaviuoral consequences. Now you can understand how complicated such research can become!
The research tells us that the most prominent brain functions involved in meditation, regardless of what the technique is, are the mechanisms that manage our attention, regulate the effects of relaxation and modulate mood. In fact the research shows that despite their different “brand names” (and price tags) most meditation techniques more or less involve these same functions. Much of these findings have emerged from fMRI studies of the brain. Later in this chapter we will see that there is evidence now available indicating that the mental silence of SY does have some unique characteristics in addition to the phenomena that occur in common with most mediation methods.
For example, when a meditator moves their attention away from external distractions and focuses it on an object or mantra networks of neurons in the frontal lobes and also parietal lobes are activated. If the meditator brings their attention inside by focusing on their breath or an internal body state they will in addition activate a part of the brain called the anterior cingulate gyrus (which is part of the limbic system) as well as an area called the insula. Meditation techniques that involve focus on an emotion also activate interconnections between the frontal lobes and the limbic system. The frontal lobes and the interconnections between the frontal lobes and limbic system are thus an important part of the meditative mechanism.
The sense of relaxation that occurs during most meditative practices appears to involve similar regions of the brain as those mentioned above but in addition to structures such as the amygdala, which is a centre in the limbic system involved in the experience of fear (and hence the fight or flight response) and parts of the thalamus which is involved in physical regulation of the body. This makes sense since relaxation can only occur when the emotion of fear is reduced, and is associated with specific events in the physical body such as the reduction of blood pressure, reduced activation of muscles, decrease heart rate and all the other features of the relaxation response that were described in chapter XX.
The improved mood that most meditators report as a result of meditation also appears related to changes in activation of certain brain structures. It is well known for example, that the left frontal lobe tends to deal with positive feelings, what we would describe as happiness while the right lobe seems to deal with negative feelings. When the right lobe is more active than the left, we tend to have more negative feelings than positive, for example. These emotions are generated as a result of interactions between the frontal lobes and the emotional core of the brain, the limbic system. During meditation several studies have shown increases in those parts of the brain that deal with positive feelings, namely the left frontal lobe and its interconnections with the limbic system. Indeed other studies have also shown increases in neurotransmitter chemicals such as serotonin, endorphins, dopamine and even melatonin in the brain and blood stream that are associated with positive mood, many of which are produced in the limbic system.
There are a small number of good studies that provide important and fascinating clues about mental silence. It appears to involve the frontal lobes and the limbic system presumably communicating with eachother through the fronto limbic loops in a pattern that is symmetrical across both halves of the brain. However, as the meditation experience increases the changes that occur at the frontal lobes seem to spread sideways and backwards to include the parietal lobes and possibly more.