Does anyone here has the experience with Sensory deprivation tank / isolation tank? Ajahn Brahm mentioned in his book The Jhana about the disappearing of the five external senses, will this be easier to achieve with Sensory deprivation tank? (Hows a tank like: YouTube)
Can the light (Nimitta) experienced before entering appana samadhi as described in the Visuddhimagga, a form of hallucinations caused by sensory deprivation?
Is the following info explained why we still see lights (nimitta) when we meditate with eyes closed?
TED Talk by neurologist Oliver Sacks: https://www.ted.com/talks/oliver_sacks_what_hallucination_reveals_about_our_minds
Does this mean that you could hallucinate too if you were deprived of sensory input? Yes - though as with Charles Bonnet syndrome, it seems to vary from person to person. There have been various experiments with sensory deprivation. A recent example was published in the Journal of Neuro-opthalmolagy in 2004, by Lofti Merabet, Alvaro Pascual-Leone, and their collaborators (Merabet et al., 2004). They simply blindfolded thirteen healthy volunteers for four days - otherwise, their volunteers were able to walk inside and outside, talk to others, and listen to the TV. 10 out of 13 people reported hallucinations. Just like in Charles Bonnet syndrome, these were sometimes simple (flashing lights, geometric patterns) and sometimes complex (landscapes, people, buildings, sunsets - often seeming extremely vivid; more vivid than normal visual perceptions).
Finally, an interesting speculation that may haunt you as you read Sacks’ book is that hallucinatory experiences - which, as Sacks points out, are much more common than one might think - could be responsible for the religious, mystical, and paranormal parts of our culture. For example, Sacks points out that Joan of Arc’s visions are classic manifestations of epileptic activity in the temporal lobes.
Well, it seem the phenomenon of Nimitta fit into something similar to Charles Bonnet syndrome by the explanation from Oliver Sacks. However, we can only know what actually happened from a neurologist perspective if meditators have their brains scan during they are having the Nimitta .