Brain has always been a mystery for scientists. But with the development of information technology, many scientists have ventured to explore this complex organ in human body and its mysterious ways of functioning. While its physiological functions are known to the medical world, there are many more which are not in the realm of physical exploration, whereas these functions controls the functions of other organs of the human body.
Sages in India had mastered the mind or brain to control body functioning, but modern science always questioned such therapies, for want of validated results. Now, again scientists have started to go back to mythological wisdom of Indian sages to correlate with modern theories of medical science.
Meditation is one technique mastered by Indian yogis. Unlike the general perception, it is not always related to worship or devotion.
The question of how meditation affects the brain and the body was posed by several modern scientists to commence research on that topic. Indeed, meditation is not an easy science although there are several scientific studies on the role of meditation with correlations to physiological and psychological conditions.
Neuroscience and Experiments
At the basis of our thoughts, emotions and behaviour is our brain. The brain is composed of several electrically excitable cells called neurons and several other structural support cells called glia. Waves or rhythms are generated by the brain when activity in these cells happens. Neuroscience researchers now measure brain waves using sensors and electrodes placed on the scalp or on the brain directly. Patterns of activity in the cortex of the brain generate electrical signals that can be detected as an electroencephalogram, better known as an EEG. Today, when such waves are measured, they are identified in terms of speed, usually recorded in Hertz (a unit to refer to cycles of activity) and are distinguished into bands ? slow, moderate and fast waves.
Several meditation studies often use non-invasive techniques like electro encephalography (EEG) to measure meditation readings. As brain signals, neurophysiologists classify these readings as infra-low, delta, theta, alpha, beta and gamma waves. The infra-low waves are less than 0.5 Hertz (Hz) and are otherwise known as slow cortical signals. Not much is known of these waves although they are usually associated with our higher brain functions and with how our brain circuits process timing and network function. Delta waves are in the range 0.5 Hz to 4Hz and are associated with deep sleep states. Several studies report observations of augmented levels of delta frequencies in a meditative mind. Delta waves are also correlated to deep sleep and its link with healing and regeneration. However, this seemingly valid observation of increased delta waves cannot be interpreted directly or as a standalone measure, since some brain abnormalities are also associated with increased slow wave activity.
A study by Alberto Fern�ndez and others in Journal of Psychiatry and Medicine in 2005, indicated higher delta and theta frequencies in patients with schizophrenia. Schizophrenia is a mental disorder characterized by abnormal social behaviour and failure to understand what is real. In fibromyalgia, a condition affecting muscles and soft tissues, delta waves were noticed to be predominant in patients. Small children have been known to show delta waves during sleep. Delta waves are also associated with deep meditation or dreamless sleep.
Theta frequencies are observed in 4-7Hz range and are associated with sleep, learning and memory. Theta rhythms of the brain are also indicated to drive learning and memory processes in neural circuits. Theta waves in EEG are associated with drowsiness, dreaming during REM sleep and some deep meditation states but not with deep sleep. Alpha waves are in the range of 7-12 Hz and associated with in deep relaxation and usually when the eyes are closed, or during light meditation. Some studies even indicate 10 Hz in the alpha waves as a fulcrum of the brain between quiet waking and lower or higher activities.
Although alpha waves have been associated with mental calm, in a study by Tomas Johanisson of University Hospital, M�lndal, Sweden, alpha waves were also known to indicate extroverted and introverted personality traits in individuals. Beta waves usually in the range of 12-40 Hz are often associated with alertness and cognitive focus. In a study by Yang and colleagues of NIH in the US, abnormal beta waves have been implicated with Parkinson?s disease.
Analysis of beta waves is also done to look into stress, anxiety and restlessness. While beta activity is crucial to identify intellectual activity and outward focus, high Beta activity may have correlations to conditions such as anxiety, obsessive-compulsive disorder, irritability, agitation, insomnia, bipolar tendencies, and substance abuse. Gamma brain waves are the fastest signals and correspond to higher cognitive activity of 40Hz or more. Psychologists and cognitive analysts associate it with intelligence, enhanced memory, compassion and natural feelings of contentment. Low gamma waves have been associated with people suffering from attention deficit disorders, depression and learning disabilities.
Brain Waves and Meditation
Early studies on meditation from a neuroscience angle started with measuring brain signals using electroencephalography.� Several scientists have studied the correlation between meditation and brain activity since the 1950s changes in the frequencies of the brain signals. Meditation studies have also shown that while long term meditators experience better coherence of activity than short term meditators.
Biochemistry of meditation
Biochemists and molecular biologists have also looked into the indicators of meditative effects through what are called as biomarkers. Biomarkers are naturally occurring molecules, genes, or characteristics by which a particular pathological or physiological process, disease, etc. can be identified.
A study by Dr. Vandana Balakrishna and colleagues from Amrita Institute of Medical Sciences had looked into adrenaline and cortisol assays on student integrated Amrita Meditation techniques. �The level of cortisol may suggest health problems related to adrenal glands or pituitary gland. Cortisol release is observed with increased physical or emotional stress levels in certain cases and illness in some cases. The body has two adrenal glands, one located above each kidney. Hormones secreted by these endocrine glands help to regulate many body processes. Measuring blood and urine levels of adrenal hormones also help body?s state of relaxation or anxiety. Vandana and colleagues had reported the practitioners Meditation techniques showed decreased stress levels.
Other meditation-related biochemical measurements include study of salivary cortisol levels, Dehydroepiandrosterone or DHEA, Serotonin, Gamma-Amino Butryic Acid or GABA, Oxytocin, Salivary a-amylase among others. Meditation has been associated to reduce cortisol levels in several studies.
Glaser and colleagues from Maharishi International University, Fairfield have shown another biomarker DHEA-sulphate, a biological precursor of steroid-type hormones showed increase in a very significant way in meditators perhaps suggesting why mood enhancement and calmness. In an Italian study, higher levels of DHEAS correlated with less carotid artery thickening, and a lower risk of heart attack and stroke. �Another study indicated study of serotonin (excreted as 5HIAA) increased in meditators which may be read positively since depressed patients showed much decreased serotonin. Meditation studies have involved increased GABA levels that have a central role in cortical inhibition (CI), modulating cortical excitability and neural plasticity. Not having enough of GABA has been related to problems, including anxiety, nervousness, racing thoughts, and sleeplessness.
Nature of Meditation
Neuroscience and biochemical studies now suggest meditation is probably helping the brain recover from long term damages and has an active role in reducing stress levels. Some evidence on meditation altering brain maps has also been observed. In practice, by reducing stress levels, meditation allows the brain to focus better and have augmented attention capabilities compared to those who do not meditate.
Shyam Diwakar, is Associate Professor and Lab Director ? Computational Neuroscience and Neurophysiology Lab at Amrita School of Biotechnology, Amrita University
