Sensory deprivation, Nimitta and Jhana


Another thing is Ajahn Brahm mentioned lots of nimitta in his book:

" Nimitta, in the context used here, refers to the beautiful “lights” that appear in the mind. I would point out, though, that the nimittas are not visual objects, in that they are not seen through the sense of sight. At this stage of the meditation, the sense of sight is not operating. The nimittas are pure mental objects, known by the mind sense. However, they are commonly perceived as lights."

Could this similar to the hallucinations during sensory deprivation?

“Of the nine volunteers who had high scores on the first questionnaire, almost all reported experiencing something “very special or important” while inside the chamber. Six saw objects that were not there, five had hallucinations of faces, four reported a heightened sense of smell, and two felt there was an evil presence in the chamber with them.”


That makes sense to me, i.e. that the nimitta in meditation is a hallucination, albeit one that can be imbued with so much energy, beauty and rapture that it sucks your mind in and stabilizes it into a unified, stable perception.

Most hallucinations are not of that quality. E.g. most people can hallucinate a mental image in their mind by will (e.g. visualize things in their mind’s eye), dreams are certainly hallucinations, but these generally don’t have the effects of the type of meditation nimitta described by Ajahn Brahm.

But in general, the mind already has the ability to create mental images far beyond the things we actually see through our eyes (pink elephants on parade!), and a lack of inputs to the five senses probably enhances that ability.


The floatation tank doesn’t cut out the senses- you can feel the water, warmth, light glow though the eyelids etc. Samatha meditation on the other hand is about a journey inwards and that withdraws the mind continuously inquiring after the senses and give rise to samadhi. Samadhi is absent in floatation tanks as I discovered! Its not enough to go to a quite place, close one’s eyes and sit still -its important to focus on some object to develop samadhi.

Yes however a floatation tank is an interesting place to meditate. Nimittas arise from the mind being purified (phabassara citta), which gives rise to bliss and rapture at the same time.


The water and the air temperature inside the tank is heated to about 34 degree, near to our body temperature. Sound and light are totally cut off inside the tank.

"If" samadhi practise require to totally cut off the 5 external senses, the tank seem like a perfect controlled environment. Of course, you still must meditate inside the tank and not day dreaming inside.

"If" nimitta is a prerequisite before entering Jhana, then is the hallucination caused by sensory deprivation help the meditator (who struggle) to see nimitta much easier? And why one has hallucination during sensory deprivation? It seem to be trick of our own brain, check this:

“eventually, your brain finally has enough: if you aren’t going to furnish it wish sensory input, then it’ll make some on its own. And so, it will start generating int.”

However, tank is not free! But you own room and air to breath is totally free! :slight_smile:

With Metta


Hi justletitgo:

It’s perhaps slightly off topic, but I presume you are using “nimitta” as a shorthand for samadhinimmitta or cittanimmita. The term nimmitta has to do with “signs” or “features”, and it used in many contexts. See, for example:

Concentration signs are discussed at the end. I collected some of the Nikaya references here: Suttas mentioning tranquility and concentration nimittas - Dhamma Wheel
I don’t think it’s accurate to call them “hallucinations”. That doesn’t seem to be what the suttas (or commentaries) are talking about.



B. Analayo:“Once one is able to preceive this object without needing to actually seeing it”.

In breath meditation, this object is mostly seen as beautiful light as mentioned in Ajahn Brahm book. Any whats the reason behind that sensation of breath can turn into beautiful light (nimitta)? Is it because of the lack of sensory input, and the brain start to create its own (hallucination)?

With Metta


I was always under these impression that these mentally constructed experiences - visions, lights, psychedelic visual or auditory imagery, waking dreams, whatever - are no less objects of worldly attachment and bewitchment than the ordinary sensory forms we encounter through the ordinary working of our five senses. To the extent that they occur during practice, one should attempt to set them aside and let them go, not indulge in them as objects of enjoyment and fascination.

I don’t think this comes from the Pali tradition, but I believe the Sanskirt Buddhist meditation tradition has some saying like, “If you see the Buddha on the path, kill him.”


That’s Linji from Chinese Chan. See Linji Yixuan - Wikipedia


I think these hallucinations are more likely driven by ramblings of the mind. Strong emotions generate mental images, and in the dark they may manifest more IMO. Nimittas are a vision of exceeding purity of the mind, and citta ekaggata or one pointedness of mind is required, but the sensory deprivation might help reach a nimitta more easily. Though floating isnt the posture I’m used to meditating in :laughing:.


My own speculation is that when a lot of energy and joy accumulates in a single, stable perception, a strong light is just how we experience that.

Just like a strong light in the physical world is actually an accumulation of many photons, yet we don’t see photons, we see brightness. Brightness is just how we experience ‘many photons’.

I think most of our experiences even when we have full sensory input are hallucinations as well. Or in other words, human perception is not a camera passively taking in an external world, but something that actively constructs the sphere of experience we live in (see link below :slight_smile: )

So you could say the brain is always creating its own hallucinations, but it gets more powerful in the absence of the five senses? Maybe, I don’t know.

According to the Ajahn Brahm method, you can use the light nimmitas to take you out of the five sense and into the sixth sense (the mind). That way you experience that the five senses are not permanent, and their absence gives you a better idea of what the five senses are.

Furthermore, according to the Ajah Brahm method, since the pleasure of a good nimitta is non-sensual, there’s no harm in indulging in it (in fact you should to get you into jhana).


Thanks! I have also watched Anil Seth TED Talk Anil Seth: Your brain hallucinates your conscious reality | TED Talk which is fascinating!

Here is the rubber hand experiment

We are born into this body, and we drag this body along till the day we die. Same for the other 4 Khandha! But it is just bunch of hallucinations! :sweat_smile:

Lord Buddha notice this 2500 years before Anil Seth! :stuck_out_tongue_closed_eyes:

And how is a person ailing in body and ailing in mind? It’s when an uneducated ordinary person has not seen the noble ones, and is neither skilled nor trained in the qualities of a noble one. They’ve not seen good persons, and are neither skilled nor trained in the qualities of a good person. They regard form as self, self as having form, form in self, or self in form. They’re obsessed with the thought: ‘I am form, form is mine!’ But that form of theirs decays and perishes, which gives rise to sorrow, lamentation, pain, sadness, and distress.


Hi Justletitgo,

I saw your post some time ago, but as I’ve been away on retreat and so on, I just now got around to responding. Sometimes it takes a while for my addled old brain to digest things and see something useful to say.

In my oft-misbegotten youth, my friends and I would from time to time use a float tank, so I have some idea of the kind of experience they offer. But that was way before I started meditating, so I haven’t meditated in a float tank, nor can I directly compare the experiences, I can just compare meditation with my memory of a float tank.

Floating was a lovely experience. There was nothing like a process or intentional path: just get in and see what happens. Much of the time in the tank is probably spent hovering back and forth on the boundaries of sleep. It didn’t feel like a particularly expansive or transformative state of consciousness, but it was pleasant, and afterwards there was a gentle and peaceful sense, almost a tingle of aliveness.

I don’t believe, however, that we can really compare this directly with meditation per se. And I came to realize that the key problem was the use of the word “deprivation”. Deep meditation is not a state of being “deprived” from the senses, but of being “freed” from them.

Let me say, I reject utterly the distinction between so-called “Visuddhimagga” and “sutta” jhanas. It is unsound scholarship. The distinction has a passive-aggressive ring to it, pretending at scholarly grounding yet hiding a clear value-judgement, subtly dismissive as it claims to illuminate. This is not how scholarship should be done; and to be clear, it is not something that I would acknowledge as meaningful scholarship or research at all. We would all be better off had this false distinction never been made.

As far as I’m concerned, there are just jhanas as taught by the Buddha and the Buddhist traditions. In the last few years, a few teachers and practitioners in western Buddhism, having caught up with the idea that jhanas are actually a thing—which we have been teaching for decades—describe some of the initial steps on the way to deep meditation as if they were jhanas. The states they describe are familiar to an experienced meditator. They are part of the journey, yet there are also states that lie well beyond their ken. For jhanas are deep and profound, they are the very doorstep to nibbana. The sages of old gave up everything, retreating to the forests and mountains for decades to practice them, often trying and failing. It is of these elusive and profound, subtle states of transformed consciousness that I speak. I have written and spoken extensively on this topic, so I will not repeat all that here, but will focus on trying to frame a response to your question.

The senses are suffering. O, how much suffering! Sights are a pain, an impulsion, a striking of noise on the eye. The eye, the physical organ, is so supremely sensitive, it expands and contracts to let in light or keep it out, adjusting for vast differences in the quantity of light, coping with the glare of a sunny Australian beach and able to detect even just two photons when fully dark-adjusted. So sensitive is the eye! All that information must be sorted, processed, recognized, at a tremendous cost to the brain. Think of how vast the processing power it takes a modern computer to process images and run neural nets, just badly and coaresly recognize a few patterns in a photo. We do far more, with extreme precision and accuracy, every moment, without even being aware. And the sight is just the beginning! Each sense is an impact, a striking, a harsh and irrefusable demand by the outer world. Our sense mechanisms are digesting and making sense of all this, passing the information over to the brain, where our mental model of the world starts to be constructed and continually updated.

So for all our attachment to, and hungry pursuit of, pleasures of the senses, it is still a blessed relief to be freed from them. To step into a quiet forest, to plunge under the ocean surface, or even to sink into a float tank, all give at least a degree of relief, a slowing and quieting of the flow and demand of sensory load.

The experience of deepening in meditation is the pleasure and relief of freedom from these senses. Even in ordinary states of mind, we speak of being “immersed” in a good book or a reverie. Our senses can be relatively neglected, and as our focus sinks into what we love, we lose awareness of what is around. Notice that even at this shallow level, there is a distinct difference between the experience of trying to concentrate on a book, which will never result in immersion, and losing oneself in a book that one loves.

It should go without saying that here, as with every aspect of the mental cultivation of transformative consciousness, the terms we use to describe everyday states of mind have but a coarse and approximate relation with the realities that manifest in the process of meditation. For these things, there simply is no common shared experience upon which to build a well-understood vocabulary, so we must rely on metaphorical stretching of everyday terminology.

The experience of freedom from the senses is not deprivation, but fulfillment. Released from the tugging and pulling, the poking and the prodding of the damn senses and their pain, at last there is peace. Think of how sensitive the eye and other senses are: then know that the mind is infinitely more so. It is so unspeakably tender and gentle, like a baby, prodded by the needles and probes of sense experience.

If we think of deep meditation as a state of “deprivation” it makes sense to think of what is envisaged in that state as a “hallucination”, that is, as a false simulacrum of reality, concocted by the mind to make up for the sense experience from which it is deprived. But if the experience is one of wholeness and fulfillment, of a blissful immersion in light and joy, then we need a different way of talking about these things.

The suttas do not use the word nimitta to mean a light seen in meditation (as I pointed out in my first book, A Swift Pair of Messengers). Rather, nimitta in the context of meditation, means “an aspect or quality of experience that, when focused on or brought to awareness, tends to promote the growth of similar or related qualities”. The use of the word nimitta especially for the preliminary development of the light in meditation was introduced, or at least popularized, by the Visuddhimagga, and should not be back-read into the suttas.

The use of terms denoting “light” and “radiance”, etc. is pervasive in the suttas when speaking of such profound states of stillness. Indeed, as I have pointed out elsewhere, the very words jhāna and samādhi both have a sense of “light” to them, and might be translated as, say, “illumination” and “incandescence” rather than “absorption” and “immersion”. Other words like obhāsa, pabhassara, pariyodāta and so on are constantly used in the context of jhana. And in many places similes of light are used quite explicitly as well.

The mind is the knowing. It is awareness. The nature of the mind is to know, but normally much of its energies are taken up with the task of lesser knowing: that is, accepting and making sense of the masses of information that flow through the senses. This is essential for survival in this realm, but it takes its toll. But when freed from this constant stream of impacts, the mind flowers open, tender and joyous, relaxed and gentle, free at last. No longer cowering and protecting itself from whatever might strike it, it has trust and clarity. Finally it can “know” in a better, deeper, higher way. It is ready for insight.

For a meditator, it is practically useful to find a place of peace and quiet, to help set the scene and get them on their way. Especially as the mind is starting to become quiet, any sound or other impression can readily jolt one back to awareness.

In principle, perhaps it may be the case that the deeper sensory quiet of a float tank can help with this process even further. Perhaps; and ultimately that would be a matter for a meditator to find out for themselves. However, I suspect that for most it may be too much of a good thing. A certain degree of physical alertness is required, and a little discomfort tends to stimulate the mind, avoiding drifting off to sleep. Even sitting in overly-comfy chairs often leads to a more drifty and sleepy meditation; there is a reason why the cross-legged posture is preferred. Even for those such as myself, whose knees prohibit extended cross-legged sitting, a simple chair is better than a sofa.

In the end, I think the float tank will, like most modern spiritual innovations, be found to serve a convenient purpose to help some people find a degree of peace and solace. But lacking a meaningful grounding in the overall development of a spiritual path, I fear the benefits will be quickly exhausted, and one who relies overly-much on such specialized crutches will find themselves looking for something more substantial.


I think I would get claustrophobic in a tank!


On the topic of sensory pleasure vs. non-sensory pleasure:

If I see a lush green tree, and take pleasure in my experience of seeing it, that is clearly a case of eye-consciousness conditioning sensory pleasure. If I hear someone singing, and take pleasure in my experience of hearing those sounds, that is clearly a case of ear-consciousness, again conditioning sensory pleasure.

But suppose I simply close my eyes and imagine a lush green tree, and take pleasure in my imaginative experience. That is not, I take it, and episode of what the Buddha would have called “eye-consciousness”, because it does not literally depend on the organ of sight, the eye, making contact with an external form. But nevertheless, the experience is in some expanded sense “visual”, because it is the conjuring by imagination of a simulacrum of a visual form. Clearly there is an important way in which imagining seeing a tree or imagining seeing a building are different from imagining hearing a song or hearing a burbling brook.

And the pleasures of this kind of imagination are sensory, even if those pleasures are not taken in encounters with real external objects. I think this would be the case even if the objects of imagination is more amorphous: if for example, you are not imagining a tree, but are imagining only a bright, imprecisely shaped light, or a kaleidoscopic pattern of changing colors, or a blue tunnel, etc.

If sensory imagination is stimulated, and even intensified, by substances like caffeine or other drugs, or by turning off the lights, or by floating in a tank, the pleasures of those experiences are still sensory pleasures, I would assume. The same applies to tingles and oceanic swaying experiences, and groovy floating experiences and ecstatic waves. These are imaginative inner simulacra of somatic pleasures. I don’t think the Buddha ever taught that these kinds of pleasure were a goal. And when he spoke of non-sensory pleasure, I think he had something else in mind: the pleasure of true peace and liberation that comes from the untying of fetters and abandonment of all of these kinds of stimulation and titillation.

Nevertheless, although these internal, imaginative pleasures aren’t the goal of the path, I suppose in certain circumstances they could be regarded as a kind of progress, because they tend to arise when other kinds of more ordinary pleasures are abandoned. To use the Buddha’s customary poetic figure and personify the phenomena, when one abandons the delights of the natural world and the pleasure houses, Mara will flood one’s mind with pleasurable inner substitutes in order to keep one attached to something impermanent and not-self in the stream of becoming.


It’s a gradual path, of valuing ever sublime and subtle experiences over the grosser ones, until finest, is nibbana!


Thank you Bhante for such a long and detail reply!

I deliberately mentioned Visuddhimagga Jhana because the hallucination from sensory deprivation one experience look similar to the nimitta as described in the Visuddhimagga, which seem not found in the sutta. It is not my intent to raise another Jhana War here! :zipper_mouth_face:

In Ajahn Brahm book’s, The Jhanas, he describes nimitta as light as well:

Nimitta, in the context used here, refers to the beautiful “lights” that appear in the mind. I would point out, though, that the nimittas are not visual objects, in that they are not seen through the sense of sight. At this stage of the meditation, the sense of sight is not operating. The nimittas are pure mental objects, known by the mind sense. However, they are commonly perceived as lights.

From a neurologist perspective, one can still “see” without sensory input from the eye is due to the activities at our visual cortex. We might only get a “scientific” answer when a meditator’s brain is scanned when in the process entering Jhana! :sweat_smile:

Many of us find Wordsworthian “intimations of immortality” in nature, art, creative thinking, or religion; some people can reach transcendent states through meditation or similar trance-inducing techniques, or through prayer and spiritual exercises. But drugs offer a shortcut; they promise transcendence on demand. These shortcuts are possible because certain chemicals can directly stimulate many complex brain functions. - Oliver Sacks
Source: Altered States | The New Yorker

As for the word “deprivation”, actually they now have a better name for it REST - Restricted Environmental Stimulation Therapy, which feel much nicer for meditator! :wink:

With Metta


Sensory pleasure —> Imaginary sensory pleasure —> Free from desiring sensory pleasure —> … ----> nibbana!

In the same way, when these five hindrances are not abandoned in himself, the monk regards it as a debt, a sickness, a prison, slavery, a road through desolate country. But when these five hindrances are abandoned in himself, he regards it as unindebtedness, good health, release from prison, freedom, a place of security. Seeing that they have been abandoned within him, he becomes glad. Glad, he becomes enraptured. Enraptured, his body grows tranquil. His body tranquil, he is sensitive to pleasure. Feeling pleasure, his mind becomes concentrated.

With Metta


Hi @justletitgo,

I think Ajahn @sujato has largely answered your questions. :slight_smile: To add, Ajahn Brahm had mentioned before that MN128 (the Uppakilesa Sutta) repeatedly talks about nimittas, but also to the perception of “light and form”. You can see it here: SuttaCentral

Also, re Ven Yuttadhammo’s critique, Ven Yuttadhammo himself wrote that he did not finish reading “The Jhanas” before his critique. So there is a strong probability that his critique was not based on a full understanding of Ajahn Brahm’s writing.

To my understanding, the assertion that “jhana” is simply meditation, rather than distinctive meditation states, does not gel with the Chinese Agamas. In the Agamas, the jhanas are explicitly referred to as “initial jhana”, “second jhana”, “third jhana” and “fourth jhana”, and described as distinctive states of meditation (e.g. vitakka viccara is described using different Chinese characters, compared with vitakka viccara in other non-meditation contexts).

That’s all I have to add: hope the above is helpful. :slight_smile:

With much metta,


Hi @pjteh,

Thanks for pointing out MN128 to me.

Here is a research paper about light experiences during Buddhist meditation from a neurobiological perspectives: A phenomenology of meditation-induced light experiences: traditional buddhist and neurobiological perspectives

Investigating meditation-induced light experiences suggests that on account of restricting attention by deselecting sensory stimuli, certain meditation practices may function in a manner analogous to sensory deprivation and perceptual isolation. The arising of lights may signal a period of enhanced neuroplasticity and potential for important and enduring shifts.

Off topic a bit, in the beginning of MN128, the Venerables are arguing, quarreling, and even fighting! I am curious what kind of War are they having then! :blush: And it is totally inconceivable and astonish that they won’t stop even after Lord Buddha asked them to, for 3 times! :astonished:

With Metta


Jhanas are nothing to start a war over. There are two views: easy-jhana and difficult-jhana, relatively speaking.

People who hold to the EJ-view, think that EJs are what the Buddha originally taught, and hence that they are sufficient to qualify for the right concentration needed for arahantship. They acknowledge that DJs exist, but they are not necessary for full awakening.

People who hold to the DJ-view think DJs are what the Buddha originally taught, and hence that they are necessary to qualify for the right concentration needed for arahantship. They acknowledge that EJs exist, but they don’t think they are actually jhanas, and while necessary on the path to DJ, they are not sufficient.

What is the practitioner to make of this? Why not practice as if the DJ-view is correct? If the EJs turn out to be right, you may receive the bonus of becoming an arahant prior to actually attaining DJ, and if the DJs turn out to be right, you’ll actually need to master DJ :slightly_smiling_face: