There are three main nadis in the human system
Ida on the left, Pingala on the right and Sushumna in the centre.
IDA NADI
"The left side channel is called Ida Nadi and is connected to the right side and the back of the brain. The two, left and right channels, cross at the Agnya Chakra. This channel caters for the left sympathetic nervous system. This channel looks after our emotional life and our past. It is the channel which creates our past. Whatever is the present today becomes the past tomorrow. The subconscious mind receives information from this channel. The sub-conscious mind has an age-old Collective Subconscious mind beyond it. Everything that was in the past since creation resides dormant in the Collective Subconscious. This Collective Subconscious has all that is dead in the evolutionary process collected and stored. Whatever is dead or gone out of the circulation of evolution and also whatever is spilling out of the subconscious mind goes out into the Collective Subconscious mind."
--H.H. Shri Mataji Nirmala Devi
PINGALA NADI
"The right side channel is called as Pingala Nadi which crosses Ida Nadi at Agnya Chakra level. It is connected with the left side and the front of the brain. This channel caters for the right sympathetic nervous system. On the right hand side is the supraconscious mind, which creates our future. Whatever we think about our future is recorded on the right hand side, and it also has a Collective Supraconscious, which has got all that is dead, which happens due to over-ambitious, futuristic personalities, aggressive animals or plants."
--H.H. Shri Mataji Nirmala Devi
SUSHUMNA NADI
"The Sushumna is the central channel for our evolution. It is through this channel that we become Collectively Conscious and all the disparate factors of our being are integrated in one whole. It makes the connection between our conscious mind and the auto of the autonomous system, the Spirit, which is a reflection of God. Sushumna is the way of Dharma, the straight and narrow path by which we pass through the Gate of the Agnya Chakra to enter into the Kingdom of God in the Sahasrara."
--H.H. Shri Mataji Nirmala Devi