Recently I did a 5 day Darkness Retreat. No stimulus, absolute boredom.
I feel like my nervous system has down regulated significantly. My aperture for life has expanded. Looking forward to doing my next one.
I would say almost complete deprivation. No light whatsoever.
And the idea is that there are no outside sounds either, except that the place I did it wasn’t completely sound isolated, though most dark facilities are.
There are food deliveries twice a day, and I have to admit how exciting that moment becomes after a couple days.