Meditation and HD
Part 2

A look at how meditation may delay the onset of many symptoms of HD

Neuroscientists and Buddhist monks: Results of an unusual collaboration

The Dalai Lama, very much aware of neuroplasticity's potential to interact meaningfully with Buddhism, encouraged monks to lend their brains to science so the workings of their meditating minds could be explored scientifically. Ultimately, he dispatched eight of his most accomplished practitioners to a neuroscience laboratory to have them hooked up for electroencephalograph (EEG) testing and brain scanning. The tools with which cognitive neuroscientists measure brain activity have grown very sensitive, allowing scientists to observe differences in brain activity between individuals doing the same task or even between different trials with the same individual. The Buddhist practitioners in the experiment had undergone training in meditation for an estimated 10,000 to 50,000 hours, over time periods of 15 to 40 years. As a control, 10 student volunteers with no previous meditation experience were also tested after one week of training.

Electrical activity and brainwaves

Davidson et al (2004). The monks and volunteers were fitted with a net of 256 electrical sensors and asked to meditate for short periods. Thinking and other mental activity are known to produce slight, but detectable, bursts of electrical activity as large groupings of nerve cells send messages to each other, and that is what the sensors picked up. Richard Davidson, head of the experimental neuroscience laboratory, was especially interested in measuring gamma waves, some of the highest-frequency and most important electrical brain waves.

It is well known that the brain has electrochemical properites. A fully functioning brain can generate as much as 10 watts of electrical power. Even though this electrical power is very limited, it does occur in very specific ways that are characteristic of the human brain. Electrical activity emanating from the brain is displayed in the form of brain waves. Brain waves, or the "EEG," are electrical signals that can be recorded from the brain, either directly or through the scalp. These brainwaves are organized into categories, ranging from the most active to the least active in terms of frequency.

The frequency of the brainwave, measured in cycles per second, is associated with its speed. Different frequencies indicate different levels and types of activities. Delta waves have a very low frequency (below 4 hertz) and occur during sleep. Alpha waves, 8 to 13 hertz, occur at relaxed, quiet times. Beta waves, 15 to 40 hertz, are the next fastest, occurring when we are actively thinking. Gamma waves (greater than 40 hertz) have the highest frequency and are involved in higher mental acuity, including perception and consciousness. They are thought to play an essential role in nerve cell communication.

The brain contains hundreds of billions of nerve cells. Researchers believe our thoughts are created when large groupings of these nerve cells "fire," or send messages to each other, through bursts of electrical activity at the same frequency. Many scientists believe that synchronized neural firing, which occurs when masses of nerve cells fire or emit electrical signals at the same frequency at the same time, lies at the root of numerous essential cognitive functions, including memory and perception. Gamma wave activity, in particular, exerts a powerful influence on the brain because the production of gamma waves involves thousands of nerve cells moving at extremely high speeds in unison. Interestingly enough, Davidson found that the gamma waves in the monks showed much greater activation, and the movement of the waves was far better organized and coordinated than in the non-meditating students. The meditation novices showed only a slight increase in gamma wave activity while meditating, while some of the monks produced gamma wave activity more powerful and of higher amplitude than any previously reported in a healthy person in the neuroscience literature.

In addition to frequency, brain waves can also be measured in terms of amplitude, which describes the size of the wave. It is thought that brain wave amplitude is related to the amount of nerve cells present, as well as the degree of synchronization, with which the nerve cells fire. In other words, when an individual has a lot of nerve cells that fire well together, the size of the brain waves will be larger than when there are fewer nerve cells or when the nerve cells are not firing well together. The fact that the monks showed such high amplitude gamma wave activity is significant because it indicates that not only do they have a lot of healthy nerve cells, but these same nerve cells are also firing with a high degree of synchronization. Synchronizations of neural firing at high frequencies (gamma waves) are thought to play a crucial role in integrating scattered neural processes into a highly ordered cognitive act such as memory and in inducing synaptic changes. In other words, when nerve cells are firing with a high level of synchronicity (as they were in the monks' brains), brain cells are able to communicate with each other much more readily and the entire brain is able to function more efficiently. It is important to note, however, that the potential benefits of increased gamma wave activity are based upon inferences that have yet to be proven. More research needs to be done.

Gray Matter

Davidson has done follow-up studies and has concluded that meditation results in (along with increased gamma wave activity) a redistribution of gray matter in the brain, as well as a decline in the loss of gray matter. The decline of gray matter, which is natural but accelerated in HD, mirrors a decline in cognitive function and processing ability. The brain has two main layers: gray matter and white matter. The layer of gray tissue surrounds a whitish core, like the peel of an orange around its juicy interior. Gray matter is the command and control center of the brain where all the nerve centers are located. White matter, composed mainly of transmission facilitating sheaths known as myelin, simply connects the gray matter together. In the gray matter, we have motor-controlling cells and damage to these cells results in stroke. Stroke can paralyze any muscle that you can voluntarily move, including those of speech. It has been found that individuals with HD typically have a substantially reduced volume of gray matter in the brain, especially in the temporal lobe and the frontal lobe.

In fact, the decline in gray matter is so closely tied to the progression of HD that it may serve as a marker for the degree of brain atrophy. In other words, by measuring the amount of gray matter loss, researchers may be able to predict not only how much the HD has progressed, but also how much the brain has atrophied. This connection is likely due to the fact that an important brain structure known as the caudate nucleus is situated deep in the gray matter. The caudate nucleus is a nerve center that is essential for controlling movement and cognitive processing and has been investigated heavily by HD researchers. When the gray matter volume is reduced, this structure becomes less able to carry out its functions. Because it connects to many different parts of the brain, this inability to function can have widespread effects. Deterioration of the caudate nucleus and its connections to other parts of the brain results in behavioral changes and the inability to control emotions, impulses, thoughts, and movements. When it becomes damaged, the individual may be unable to experience intense feelings of guilt, shame, or embarrassment and be unaware of mistakes that are evident to others. This inability may result in a lack of self-awareness and an inability to evaluate one's own behavior, in addition to making social and personal relationships more difficult. HD researchers have also found that damage to the caudate nucleus makes it difficult for people with HD to prioritize tasks and organize their day, as well as to handle many simultaneous stimuli. Additionally, the caudate nucleus controls voluntary movement. (For more information on the caudate nucleus, click here).

As you can now see, the caudate nucleus is an extremely important structure in the brain and its deterioration (as a result of gray matter loss) directly leads to many common HD symptoms. It follows that any type of activity or treatment that is able to delay or prevent a loss of gray matter would also delay or prevent many common HD symptoms. Aging invariably leads to some gray matter loss, but this process is significantly accelerated in people with HD. Hence, it would be highly beneficial for a person with HD to incorporate activities into his/her life that may be able to prevent such a rapid loss of gray matter. Again, it is important to note that meditation has not been proven to preserve gray matter and this claim is based largely on the findings of a single researcher. Yi Rao, a neuroscientist at Northwestern University, says that the science of meditation is "a subject with hyperbolic claims, limited research, and compromised scientific rigour." Rao further goes on to say that, "Davidson is a respectable scientist, but he has put his respectability on the line with this." Davidson defends his work as the first step in a new field. "Meditation research is in its infancy." There needs to be a lot more peer-reviewed research findings in order for Davidson's claims to be substantiated.

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Last Modified: 04/12/2007

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