The Self or Atman or Brahman is responsible for three aspects of mind both materially and instrumentally.
1. Awareness of / Sense of being. सत् - अस्ति - नित्य - शुद्ध
2. Awareness of / Sense of knowing चित् - भाति - बुद्ध
3. Awareness of / Sense of experiencing. आनन्दा - प्रियम् - मुक्तम्
And Self provides psychic energy and
makes mind instrumental to mental functions.
All our mental functions are like pictures fleeting on the cine screen. The pictures don't and can't affect the screen. They come and disappear.
This fleeting nature is one aspect when we call the world is an appearance (on mental) screen.
And all pictures (thoughts, feelings, experiences, utterances, cognitions and communications, re-cognitions, moods, ideas, understanding, insight, intuition, meanings, sentences, and all mental functions) are the scenes appearing and disappearing on the mental screen - the Self, Atman, Brahman.
Mind and its functions happen and cease to happen depending on the conscious state of mind.
Mind is a combined operation of Self acting as screen - over which things (thoughts etc.) appear and disappear as pictures on a cine cine screen - the functions of mind as various psychic energy transformations, sense and action organs that tune to outer physical world and form inner phenomenal world and memory, and gives ability to communicate.
Mind getting tuned to memory and inner phenomenal world as experiences which cause thoughts, feelings, and communication takes place and cognition of outer physical world happens through sense organs. This cycle starts from speaker and absorbed as understanding or experience by the listener.
The above functions take place simultaneously in Wakeful and Dream conscious states of mind. These are various phases of mind.
In Deep Sleep conscious state mind takes rest and no mental functions take place. Sense and action organs remain dormant. No tuning to memory, inner mental world or outer physical world happens.
The peace and calmness experienced during Deep Sleep is because of absence of mental functions and mind taking rest and unavailable for activities.
This experience when being aware of itself is also termed as Bliss and Moksha - and is called Wakeful-sleep conscious state.
We must realize that whether it is memory activated as moods or inner phenomenal world activated as thoughts or feelings - during Dream conscious state or outer physical world as cognitions, both are mere perceptions fleeting on the mental screen - the Self or Atman or Brahman or Para.
Thus Atman is designated as cine screen, which is not affected by the play of happenings on the screen - the experiences, thoughts, feelings, utterances, cognitions, re-cognitions - and remains same and unperturbed throughout the show.
It will be a bit difficult to envisage the cognitions during wakeful phase of mind tuned to outer physical world through sense organs as mere projections on the mental screen. And not real - as expressed by famous Advaita expression -
Brahma sat, Jagat Mithya, Jivo Brahma eva na aparah
The word Jagat refers to appearances as experiences, thoughts, etc. on mental screen during Dream and Wakeful phases of mind.
Jiva is self-consciousness or the awareness as a particular individual and associated Ego.
As Consciousness individual and Atman are one and the same not different.
And the energy necessary for these appearances is the psychic energy issued out from the Self as energy pulses of frequency 10 Hz, reflected as brain waves. These brain waves get frequency modulated and de-modulated (between 10 and 30 Hz for Wakeful and Dream phases of mind) to be functions of mind in Speaker and Listener.
The depth of Upanishadic insight and Advaita Siddhanta is presented here.
