Definition - What does Mindstream mean?
Mindstream is a concept from Buddhist philosophy that refers to the continuity of awareness which carries on from one life to another. This can be viewed as a string of passing moments that happen either in the same lifetime or in the transitional period between one life and another.
An understanding of mindstream can allow a yogi to meditate more deeply and effectively during yoga practice as well as draw upon wisdom from past lives. It is especially important in the practice of Guru yoga, as the practitioner has to unite their mindstream with that of their guru.
Yogapedia explains Mindstream
The Sanskrit expression for mindstream is citta-santana, with citta meaning "something that is conscious," and santana meaning "eternal life-stream" or "a sequence of individual events." Because Buddhism does not include the idea of a permanent self -- as covered by the concept of anatta (anatman in Sanskrit) -- it is mindstream that explains and provides a continuity of personality from one life to the next.
Buddhists in India regard mindstream as a type of evolution of the mind. This means that karma and kleshas (states of mental torment) both act to pass our transformation to the following life.