Fluctuation in memory in Hinduism is referred to as Smriti Vritti. Smriti Vritti is derived from smriti (memory) and vritti (fluctuation).
Vritti occurs in the form of pratyaya or bodha (experiencing) of vishaya (an object). It takes one of the five different forms, namely, pramana (true knowledge), viparyaya (alse knowledge), vikalpa (knowledge arising from words), nidra (sleep) and smriti. Whenever there arises a fluctuation in the mind through experiencing an object which takes one of these five forms, it lasts for a duration which may be a moment or much longer. After the experience is over, a trace of the experience is left in the mind. This is called samskara of that experience.
The mind is a vast storehouse of innumerable such samskaras. Many of these samskaras are lost or wiped out from the canvas of the mind if, in the first place, they are not deeply, intensely, or vividly recorded or registered, for lack of interest or too mild an interest in the subject matter of the experience is left in the mind. This is called samskara of that experience.
The mind is a vast storehouse of innumerable such samskaras. Many of these samskaras are lost or wiped out from the canvas of the mind if, in the first place, they are not deeply, intensely, or vividly recorded or registered, for lack of interest or too mild an interest in the subject matter of the experience, and secondly, if the samskaras are not intimately associated with other samskaras, so that their chances of being revived are meager.
Patanjali has called such a loss of traces of past experience sampramosa (Yogasutra I.II). Those traces which are not lost in this way are apt to be revived by repetition of that same experience or an associated experience. Such a revival gives rise to the fluctuation called smriti vritti.
The memory in dreams is imaginary, while that in waking states is not so.