Transcendental meditation, based on mantra yoga, has been intensively and scientifically investigated in the last years. Scientists have recently attempted to standardise it by substituting random, neutral sounds for the traditional Sanskrit mantras. These techniques were able to bring about marked physiological changes, but to the yoga-minded people these practices must seem essentially impoverished.
According to neurophysiological investigations, our brain hemispheres perform many different functions.*1 The dominant (mostly left) hemisphere has most of the functions of speech, logic, critical judgement and sequential ordering. The non-dominant (right) hemisphere appears to mediate intuitive, emotional and visuosipatial relationships, pattern recognition and parallel rather than sequential function. The right hemisphere seems also connected with psi and creativity.*2 Maladaptive programming of the right hemisphere, which cannot be easily accessed through the conscious dominant hemisphere, may influence bodily functions and cause psychosomatic diseases.
The repetition of mantra stimulates the speech centre located in the dominant hemisphere in the vast majority of people, and temporary inhibition of the critical and analytic function of the dominant hemisphere takes place. This immediate effect may be caused by the repetition of any word and may explain the positive results obtained in the scientific studies of mantra yoga. However, I believe that in addition, the traditional mantras, by their particular sounds, rhythms and vibrations, also reprogram the right hemisphere after systematic and long term practice.
Another argument against the use of neutral sounds as mantras is their lack of emotional significance. During meditation, dreadful or unpleasant thoughts may appear. When the practitioner has faith in his mantra, and it is connected with positive emotion, it is easier to get over unpleasant moments than if only emotionally uncharged sounds are being repeated. Nevertheless, according to yogic tradition, the faith in mantra is not an inevitable condition for its effectiveness. The above described mechanism could be described as counter conditioning in modern terminology.*3