Shark Brain

Some species of shark must continually swim to avoid asphyxiation. Something along the same lines is true of the human brain. Deprived of all inflow of 'normal' sensation, it must create its own (q.v., John Lilly's hallucination-inducing isolation tank experimentation). Impressions are "food" for the brain, grist for the mental mill, and without them you die. So easily understood by everybody vis a vis the physical body and its sustenance. But for the brain? A complete blindside for human consideration and edification. When did it ever strike you as the case? Be honest.