This sensation of the mind racing faster and faster and spiraling (upward or downward depending on your disposition), filling with air and ballooning into a chaotic vortex of thoughts, images, and psychic forms. The imagination (image-in-motion) run amok.
Remember that the ego function (the self-aware visualization of the imagination) is a tool that blossomed forth from humanity so we could remember the past and predict the future to improve our life and chances for survival. The ego likes to think it is in charge but in fact it is but one organ within the overall TOTAL ORGANISM which is you. The Psyche. The oxygenation of blood throughout your brain and body that forms your human consciousness.
Yoga and meditation are simply words gesturing towards activities which can be done to reign in the impulses of the anxious mind by aligning the spirit/imagination with the physical reality of your brain and body. Finding balance unique to your sense of perception.