Neurology in Hinduism is known as tantrika vijnana. Tantri means nerve and is also called nadi. According to Shiva Samhita, nadis are like the fibers of a lotus and, being supported by the vertebral column column, are spread all over the body. Thus conceived, the tantrika system is accorded great significance, particularly in Yoga Shastras (ancient Sanskrit texts on Yoga).
Nadis are a conduit for the vital breath or pranas to flow and keep the body alive and conscious. According to Yoga Shastras, the universe is composed of two substances – akasha (ether) and prana (vital air or cosmic energy).
Everything that has a form evolves out of akasha. It is akasha that becomes air, liquids, solids, the human body, animals, plants, etc. And everything we all energy, or force, evolves out of prana. In all forms of life, prana, is present as a living force and all force is based on prana; it is the origin of movement, gravity, magnetism, physical action, and the nerve currents, which flow through nadis.
According to an ancient belief, there are 72, 000, 002 nadis or tantrikas. They are said to be situated behind the navel of the human body, hunched into a sprout, inside which kundalini, the primal energy, lies coiled like a serpent. Among these, the sushumna nadi is the main conduit for the flow of the vital air, supported by two principal nadis called ida and pingala and twenty four other major nadis. Their fount is actually called granthi (ganglion limper), which is situated exactly between the anus and the genitals. From here proceed the twenty-four nadis – ten upward, ten downward, and two each sideways. Ten of them carry air or vital breath. These nadis are positioned in chakras, the nerve centers.
Of ten nadis, ida, pingala, and sushumna are the most important ones. These apart, the other important nadis are gandhari, hasta jihva, pusa, yasavini, alambusa, kuhu and sankhini, the supreme one, remains centered at its very center. Gandhari is situated in the left eye, hasta jihva in the right eye, pusa in the right ear, yasavini in the left ear, and alambusa in the face.
Ida and pingala have 24 ganglia (granthis) each. According to Yoga Shikha Upanishad, they are called manis (gems). The nerve issuing from ida meets the left part of the nadi called citra, and that issuing from pingala meets the right part of this nadi (citra). In the same way, myriads of small nadis issue from these granthis and go up to the ajna chakra, which is one of the seven chakras situated between the eyebrows. The other six chakras are muladhara, situated at the base of the spine where kundalini rests in the static form; svadhisthana, between the navel and the genitals; manipura, in the area around the navel; anahata, in the heart region; visuddha, in the throat region close to the thyroid gland, and sahasrara on the top of the head.
These chakras, also called lotuses (whose petal and colors are revealed as kundalini touches them), are believed to be the vortices or whirlpools of pranic energy at specific areas in the body, which control the circulation of prana permeating the entire human structure. Chakras indicate the fullest potential of each and every person, i.e., he can transcend his individual limitations. The lowest chakra, muladhara, represents the level of a person, where there are several limitations both in knowledge and ability. Higher chakras show how a person can progressively transcend his limitation and attain his fullest potential.
When kundalini or the cosmic energy is aroused as a result of appropriate Yoga posture (asana) and pranayama (exercises and meditation), it makes its way upwards via sushumna, passing through chakras, one after the other. Whenever it reaches a new chakra, the yogi (aspirant) attains a higher level of consciousness.
Yoga Sutras believe that, through the control of physical conditions achieved by activating this nervous system or nadi network, all bodily junctions can be subordinated to the mind. Faculties may be acquired such as clairvoyance, telepathy, knowledge of the past and future, ability to read other people’s thoughts, as well as many other occult powers, depending on the chakra upon which one is meditating. When kundalini reaches the highest chakra, the aspirant realizes his full potential and attains the highest state of mukti or nirvana (complete liberation).