Some scientists have stated that we only use about 10% to 20% of our brain power. This is highly inaccurate, as the brain is merely the physical mechanism, the camouflage mechanism, through which the mind functions, much like a TV set operates through the signal from the broadcasting station.
If you destroy the TV, for example, you do not destroy the signal, and when one dies, the brain of course dies however their mind-personality-identity-persona–ego survives physical death and continues. The mind is not dependent upon a brain from which to operate.
There are many dormant, unused areas of the brain that may or may not be activated in the personalities lifetime, or perhaps a few are. Such mental-belief actualization can be likened to a veil lifting in the brain allowing other information to be accessible or begin coming through, and here, Seth is saying that physical stimuli, as in psychedelic substances, can act as an aid in opening up these areas of the brain. Such psychedelic materials are not the only method of opening these inner doorways, however.
Seth: “Those portions of the brain, seemingly unused, deal with these other dimensions, and physically, you begin to use these portions, though minutely, for the first time, under psychedelic situations.”
The Early Sessions, Book 7, Session 308