Upanishad is one of the structuring dynamics of Rk Veda. It highlights the TRANSCENDENTAL and SELF-REFERRAL qualities involved in structuring Rk Veda. With reference to consciousness, Upanishad comprises the specific sets of laws of Nature that are engaged in promoting the quality of Rishi — the observer, the witnessing quality — within the Samhita level of consciousness, providing a structure to the eternally silent, self-referral, self-sufficient, fully awake state of consciousness, which is intimately personal to everyone. (complete table of qualities)

In the physiology, Upanishad is represented by the ascending pathways that bring every possible sensory experience to awareness.

The ascending pathways, including the visual pathway, the auditory pathway, and all other sensory pathways, act as the channels that take every possible experience to the cortex, where it is integrated and perceived as a holistic value, such as a flower, a friend, a symphony, etc.

		— Prof. Tony Nader-Ram in Human Physiology: Expression of Veda and the Vedic Literature, pp. 184-185