i've read now many times about a specific filter between thalamus and cerebrum that prevents the brain of too much incoming signals. this shall include signals that are not necessarry for humans to survice and reproduce. the more incoming impulses the more it is filtered because everything incoming flows from the cerebrum back to thalamus preventing more to enter.. sort of
so-called "psychedelic" susbtances like lsd, psilocin, mescaline, ... are capable of removing this filter (i assume due to their serotonine blocking) and let everything get in..
i have not found true scientific reports about this matter, so i give it a try here. has anyone heard about this?