Sensory deprivation, Nimitta and Jhana


  1. 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)

  2. 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:

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 . :slight_smile:

With Metta


Greetings and welcome to the forum Justletitgo :slight_smile: We look forward to your participation



Of course it would be easier by going into the tank. The purpose is to deprive you of the senses. For those who don’t know what a deprivation tank is - you lie in a tank of salinated water with no visible light. This gives the sensation of weightlessness as if there were no body. However, and what Ajahn Brahm is referring to, we are developing states of absorption that can be entered into, with practice, at any time. Perhaps you can succeed in shutting off the senses in the tank but what you would really be deprived of is the gained patience, dedication, and endurance by doing the same thing through many hours of samatha practice. Not to mention that once you’re out of the tank any ability to achieve the same state will be lacking.

It’s also important to note that Venerable Brahmavamso is referring to the Visuddhimagga jhānas or absorptions jhānas. The jhānas referred to in the suttas do not require the disappearance of the senses. In fact the meditator, according to the suttas, is aware of the body up into the fourth jhāna.

If you have the time and interest give Venerable Yuttadhammo’s critique of Ajahn Brahm’s “The Jhānas” a read - Apparently the blog was taken down, so if that fails here’s another link

All the best


@anyatama Thanks for your detailed answer! Yes, I knew that there are many different version of Jhana. :slight_smile:

Is the following text similar to nimitta like one doing kasina/breath meditation?

The ganzfeld effect (from [German] for “complete field”), or perceptual deprivation , is a phenomenon of [perception] caused by exposure to an unstructured, uniform stimulation field.[[1]] The effect is the result of the brain amplifying [neural noise] in order to look for the missing visual signals.

It has been most with vision by staring at an undifferentiated and uniform field of colour. The visual effect is described as the loss of vision as the brain cuts off the unchanging signal from the eyes. The result is “seeing black”,an apparent sense of blindness. A flickering ganzfeld causes geometrical patterns and colors to appear, and this is the working principle for [mind machines] and the [Dreamachine]. The ganzfeld effect can also elicit hallucinatory percepts in many people, in addition to an [altered state of consciousness]"

With Metta


Thank you so much Venerable for acknowledging this very important distinction.


I read his blog post. :frowning_face:

I understand Ven Yuttadhammo disagrees with The Jhānas. But I take issue with the ad hominems toward Ajahn Brahm such as “Jhana-thumping teacher.”

1 Like

A distinction often overlooked and one of my main critiques about Venerable @sujato’s translation. It can lead to a great deal of confusion for a meditator seeking to attain jhāna. One might have already attained jhāna but not known it because they were under the impression that their senses needed to be shut off.

1 Like

Venerable, how can one know that one already attain the Jhana? Is there any significant phenomena that can be tell for sure?

Venerable Yuttadhammo’s critique, however, is not the issue and unskillful delivery doesn’t discredit the points given in that article. This was written 8 years ago and I won’t deny that his approach was at times unskillful. However, it’s not about him disagreeing with The Jhānas. It’s about him calling out the blatant distortions of the Buddha’s teachings.

We then have to ask ourselves are we more concerned with words that can be potentially displeasing or truthfully representing the Buddha.


The 1st jhāna includes the temporary abandoning of the 5 hindrances and pīti-sukha - the joy and delight that arises because of that.


Thanks for your reply, Bhante. I won’t further discuss Ven Yuttadhammo’s critique to keep the topic on topic. :anjal:


Thank-you for your post and the links. It’s always useful to look at things from various directions and perspectives as we work our way along the Noble 8-fold path.

:dharmawheel: :anjal:


And the joy and delight express themselves both in the body and in the mind that is why there is no sensory deprivation in jhana (at least the jhanas 1 to 3).

1 Like

From DN 2

“Further, great king, with the abandoning of pleasure and pain, and with the previous passing away of joy and grief, the bhikkhu enters and dwells in the fourth jhāna, which is neither pleasant nor painful and contains mindfulness fully purified by equanimity. He sits suffusing his body with a pure bright mind, so that there is no part of his entire body not suffused by a pure bright mind.

Great king, suppose a man were to be sitting covered from the head down by a white cloth, so that there would be no part of his entire body not suffused by the white cloth. In the same way, great king, the bhikkhu sits suffusing his body with a pure bright mind, so that there is no part of his entire body not suffused by a pure bright mind. This too, great king, is a visible fruit of recluseship more excellent and sublime than the previous ones.

From MN 52

“Again, with the complete surmounting of perceptions of form, with the disappearance of perceptions of sensory impact, with non-attention to perceptions of diversity, aware that ‘space is infinite,’ a bhikkhu enters upon and abides in the base of infinite space.

Unable to recall a sutta detailing the four ārupa jhānas. However, it would seem that the formless attainments (beginning with the perception of infinite space) would fit the description of absorption. Wherein the meditator is locked into a perception or object.


These have been called jhanas in the commentaries. In the suttas they are achievements. There is no sutta that describe them in the same manner the four jhanas are described with qualities such as vitaca, vikara, piti, sukha, sati, upekkhā.
Several scholars consider they are not original to the teaching of the Buddha (after all he kind of rejected two of them after learning them from his two teachers) but late corruptions of the suttas. When you search the suttas for such items like these attainments and also the last five fetters you always find them in a kind of list without any explanation of what they are, how to achieve them and, more importantly, of their role on the path to ending dukkha. The fact that they are not mentioned in any of the suttas that talk about the Buddha’s awakening is a strong indication that they are not needed and not part of the Buddha dhamma.

1 Like

Indeed calling them jhānas was a slip of the fingers.


Ven. @anyatama, @alaber

Please be mindful of this thread’s topic which is asking about people who have experience with sensory deprivation tanks.

If you want to discuss the nature of jhana specifically, you can create a new topic that is linked to this thread (link icon at the bottom of a post -> new topic).

Linking is a good practice because it let’s interesting discussions continue without hijacking the OP’s thread :slight_smile:


Sensory deprivation seems like a kind of crutch to me. By contrast the suttas describe the Buddha as meditating without perception even as a noisy series of carts drove past him.

If we take this not as a pious embellishment, but as a guide to practice, then perhaps we should at least sometimes seek out noisy places to meditate. That way we can know exactly when we have reached a similar absorption.

No, I haven’t tried it yet myself. But it has been a frustration in my practice that never once has the closing bell at the end of a meditation session failed to bring me back to ordinary thinking. I would imagine that a “failure” in this department would be a powerful confirmation of the account of the jhanas that is the consensus in these forums. Alas, I’m not there yet.

1 Like

Yes there is such narrative but it is a single case and could be explained by going to the cessation of perceptions and feeling (wrongly called jhana number nine).
But the four jhanas corresponding to samadhi, the eighth component of the 8FP are not described this way. All four jhanas similes are very much talking of full awareness of the body.

I haven’t done a sensory deprivation tank, but on longer retreats you can start to “suffer” from sensory deprivation, and I have found it helpful for getting deeper and uncovering more layers of the mind.

If there aren’t external sense experiences pulling your attention away from the inner work of the mind, then you’ll naturally start to focus more and more inward, where the interesting stuff happens.