Psycho-physiological changes found in mandala visualization are used variously in Tantric rituals and practices. Tantrists often employ a mandala in order to give the initiation rite (abhiseka) to their disciples. Lay followers make worship services (puja) to a mandala or the deities depicted in the mandala. Sometimes mandalas are used as a kind of tool for meditation when Tantrists or yogins perform the practice of deity-visualization (sadhana). In such cases, the mandala meditation or visualization may have a soteriological purpose: the practitioners of visualization, i.e., sadhaka, try to obtain enlightenment through this kind of religious practice. The Tantric practice of mandala visualization is to be basically carried out through the power of a particular kind of yoga. When a practitioner or Tantrist practices visualization, he intensifies his psychic energy. It is through the strengthened and sharpened psychic energy that the practitioner can succeed in visualizing the form of a deity in front of him as if the deity were real and alive. Mandala visualization is not done in a moment; it is a religious practice which one should perform, following a series of rigid steps over a certain span of time. Usually, the accomplishment of mandala visualization requires a number of years. It is well-known that yogins should undergo a number of psycho-physiological changes for, at least, several years, before they can reach a certain stage of the system of classical yoga. In a similar way, it has been said that various kinds of states accompanied by psycho-physiological changes must be observed until a practitioner succeeds in performing the visualization of a mandala. What kind of psycho-physiological changes, however, are found in the mind and body of the practitioner who has just succeeded in visualizing the form of a deity? One should remember that the so-called psycho-physiological changes, if any, are not to be confused with the symptom of obtaining final enlightenment. As mentioned before, mandala visualization may aim at the soteriological purpose of obtaining Final enlightenment. But, at this point, we are rather concerned with preliminary stages of religious practice called "mandala visualization," not with the state of the mind and body of the one who has obtained final spiritual beatitude. Insofar as one of the most important functions of the mandala is to furnish a tool for the practice of visualizing deities, we should not neglect the question what kind of state occurs in the mind and body of the Tantrist trying to see the form of a deity in front of him. Hitherto the psycho-physiological aspect of the process of mandala visualization has not been well studied. The function of the mandala would be also clearer, if we could succeed in analyzing the process of visualization from the psycho-physiological viewpoint.
