Yoga has not identified the vrittis, it has only identified the nature of vrittis. The Yoga Sutras state that vrittis are of five kinds and has classified them into five groups: pramana, direct knowledge, viparyaya, false knowledge, vikalpa, imagination, nidra, sleep, and smriti, memory. Everything the vrittis do through the mind and senses is contained in these five classifications. Pramana is not one vritti; it is the nature of vrittis. Vikalpa is not one vritti; it is the nature of vrittis. Smriti is not one vritti; it is the nature of vrittis, because we have more than one memory. Once a person underwent hypnosis shortly after entering a room for the first time. He was then asked various questions about the room, such as how many windows there were, how many flowerpots, how many flowers in bloom, and so on. Under hypnosis the person was able to give accurate answers to these questions without ever having counted any of the items consciously. What does this mean? If we are able to access those areas of the mind that at present are inaccessible consciously, we realize that we know everything, because one aspect of the self, one part of the mind is always the drashta, the witnessing mind. It is not the experience itself; it is the witness of the experience. When the conscious mind is absent, it is possible to give accurate descriptions of what is happening because the mind is free from the vrittis. But we have our identification with the outside world, with the world of name, form and idea, in the world of time, space and object. Our focus is always uni-dimensional, not multi-dimensional.
The moment we are able to remove that uni-directional awareness, we become multi-dimensional people. This idea is the beginning of the yogic process. The vrittis, as defined in the Yoga Sutras, represent five compartments in which every mental state is included. Memory, for example, is not only something you have seen, recorded and lived, it is also something you have ignored, but which has been registered anyway.

So smriti cannot be one type of memory; it will be multi-directional, multi-dimensional experience in the form of memory, including the conscious, subconscious, unconscious and also the transcendental dimensions. It is the same with sleep, nidra. In nidra there is absence of waking consciousness, absence of the cognitive faculty. But even when we are asleep, the subconscious remains active and unconscious processes continue to happen. We dream and we experience in the state of sleep. Therefore, do not misunderstand the word vritti. Vritti means a collection of experiences which disturbs the ease and harmony of the tranquil state of existence. When we are unable to guide the vrittis properly, or use them to fulfil an aspiration, they become the cause of kleshas, afflictions. Our life is full of kleshas. We are always worrying about something happening to ourselves, our family or our society. Pain, suffering, confusion and conflict are afflictions. Life as we live it today is affliction. Do we continue to live that way, or do we make an attempt to improve the quality of life? Yoga aims to improve the quality of life, to change the pattern of life, so that we become aware of ourselves and our potentials, and begin to live them.

Abstract from Yoga Sadhana Panorama Vols 5 ,  Swami Niranjanananda Saraswati