It is a natural process.
The brain needs permanent clearing-up. Otherwise it would "explode" due to the overwhelming quantity of inputs.
That's called noise. Discernment is discriminating, like in a receiver. It's where one looks, focus, and that is individual, choice.
I wonder how the brain remembers, memory, across years, decades, moving pictures with sound, smells, impressions, since childhood, they tell us before, in the womb, subconscious, unexamined yet operative, possibly, likely, determinate. Even when 'it' forgets, the memory, selective, prompted, returns, if only for a moment. A matter of access, it is there. How, memory, and capacity, there is no understanding of how and no computation for capacity, not really, has a quantum, holographic quality that remains a mystery.