I also would like to clarify a point about mindfulness meditation and insight practice (vipassana). As they are sometimes mixed together. And while insight practice works, mindfulness, a stripped down version of it, doesn't. 

I'll start by referencing a paper mentioned in the post, namely "Meditation experience is associated with differences in default mode network activity and connectivity." [7] There the authors have shown that Theravada monks clearly shut down the DMN by what they call "mindfulness meditation". And describe three methods of mindfulness meditation: breathing meditation, Choiceless Awareness (the term coined by Krishnamurti Jiddu), and loving-kindness (metta) meditation. 

That might confuse things a bit. But let's look at the basic source for monk's training - Pali Canon. The basic instruction for insight and concentration practices in the tradition of Theravada is Satipatthana Sutta and Anapanasati Sutta which are unfortunately translated as "The Foundations of Mindfulness" and "Mindfulness of Breathing". The word "sati", which is translated as "mindfulness", literally means "recollection". And it is a term there that is used in developing concentration. 

What do those texts say about practice? Is it only recollection of breathing and awareness? No. They are clearly set to contemplate the Four Noble Truths, the Five Hindrances, the Seven Factors for Awakening and so on. So they are loading contradictions in thinking to contemplate upon (e.g. "I suffer" / "Freedom from suffering is the goal", "I feel desire" / "Desirelessness is the goal", etc.). I would suggest that those act as koans to contemplate during practice. So both concentration is developed (samatha) and insight is cultivated (vipassana). In one practice! 

So what does it say about the monks from the paper? First of all, they have selected monks who are awakened (who can switch off the DMN). Knowing the protocol of their practice they most likely have come to awakening through insight and concentration practices. And after that they can naturally abide in this place by just about any stimuli. But for the monks "mindfulness" means long-long years of vipassana and samatha practices. While for researchers it means the stripped down version of it (without accounting for the details how they reached that state)!

Long story short, mindfulness practice as noticing thoughts and sensations and coming back to awareness on itself seems to be not enough to shut down the DMN. It has to be full scale insight and concentration practices as described in the text (i.e. going through all the truths, factors, contemplating them, releasing attachments, etc.). And that's what monks from the paper supposedly did. 

There is a good video with one illuminating comment (pinned), Does Mindfulness Lead to Persistent Nonduality? In the comment it is said that the traditional vipassana practice by itself has a missing component: 

He [the Dalai Lama] essentially gave his blessing to the Goenka retreats but said he felt that there was a missing element. He advised practitioners to look back and try to find the one doing the meditation.

So basically the Dalai Lama recommended self-inquiry practice on top of vipassana. 

Why I decided to articulate those nuances? I feel like most of the time people confuse mindfulness meditation with insight practice and do it for years (I did so myself). I hope that clarifies things a bit. 

Not necessarily. There are two points of interest here. First, it depends what one means by meditation. If that's mindfulness meditation, there are studies that have shown that it doesn't deactivate the DMN. If we add here the fact that some people dedicate 4-8 hours per day to meditation that's a recipe for disaster as the ruminating network is working all those 4-8 hours under the hood. There is a useful post by Gary Weber, mindfulness meditation - religious vs secular - does it work? - new research that discusses this point. 

Second, if the shift has occurred without the proper preparation (i.e. the "I" is not deconstructed enough) or suddenly during the insight practice, the DMN network might try to win control back and there will be a conflict as the DMN is not shut down. That might happen if awakening happens "out of the blue" and the ruminating network is strong. That might even lead to the Dark Night of the Soul. Here is another useful post by Gary, Dark Night of the Soul?...who/why/what to do.

The key point in both is that "I" has to be deconstructed enough, which means one has to learn to shut down the DMN properly. As even after awakening it might cause trouble if one didn't learn to shut it down. A book by Suzanne Segal, Collision with the Infinite is an example how a person might struggle to integrate awakening after it occurred. 

So in the end I would guess (and please keep in mind that it's a speculation of a layman) that given the proper conditions it's not meditation itself that causes psychosis but the DMN that is hyperactive. The issue with mindfulness meditation is that it doesn't address the activity of the DMN. 

Depression is a real challenge. It's difficult to explain what it is until you've been through one. I've found the method of self-inquiry to be of help (e.g. "Who is depressed/suffering/cannot move?", "Well, I am.", "Where does this I come from?" and keep looking for the source of the "I"). 

It is postulated that self-inquiry helps to deconstruct the "I" and as a result to pacify two subnetworks (of the DMN) that are responsible for building the images of "self in time" and "self and other" (as most thoughts are build around them). So it helps in reducing self-rumination and thoughts which are supporting the depressive state. There is a nice video on that topic - dealing with thoughts by Gary Weber. 

Yes, I'm only re-quoting Wittgenstein from another book (Jay Garfield, The Fundamental Wisdom of the Middle Way), so my understanding is only approximate in that case, I could not process the Tractatus as it's way over my head. And I'll check the sequences. 

A little example how one can apply this. I have near to zero expectation about this post being understood or liked (not that it doesn't matter at all, I'm serious enough to elaborate the concepts as best I can, but beyond this it's not under my control). I also know that disappointment is dependent upon expectation so they are both empty of intrinsic nature. Therefore, I'm not anxious about people liking that text, nor I'm disappointed if it's being disliked. In that case I see that disappointment and expectation are both empty. So I'm free from both! 

What if it wasn't so? And my expectation was high (i.e. I would approach it like it had intrinsic value). I would be disappointed because of low karma. But how to get rid of that disappointment? It is to see that it's empty. How? To analyze that it depends on the expectation, and if I can let go of my expectation, I will be free from the disappointment. 

And how does one let go of the expectation (or any negative feeling)? There are many ways. First, by observing one's mind impartially and seeing it clearly for what it is (what in Buddhism is called vipassana meditation). Second, I can imagine myself on my deathbed and ask the question, "How important would it be then?" Third, I can apply a technique like The Sedona Method. In this way I can see through my constructs on the conceptual level and the level of feeling and be free from them. 

That's how the concept of emptiness might be used in practice. 

Thank you for your thoughtful and detailed comment! 

It wasn't meant to sound mysterious. The way I see it is that our process of thinking by default creates intrinsic entities and processes (whether we are aware of it or not) and almost becomes metaphysical with respect to our inbuilt ontology. In simple terms, we give too much credit to "how things really are". And I attempt to question that in order to deconstruct such an attitude (not only on conceptual level, but at the level of feeling). It's the same idea Wittgenstein expressed in the Tractatus: 

6.371 The whole modern conception of the world is founded on the illusion that the so-called laws of nature are the explanations of natural phenomena.
6.372 Thus people today stop at the laws of nature, treating them as something inviolable, just as God and Fate were treated in past ages. And in fact both are right and both are wrong: though the view of the ancients is clearer in so far as they have a clear and acknowledged terminus, while the modern system tries to make it look as if everything were explained.

Why am I writing this? In part, when I want to understand something better I try to express that to other people. It helps to consolidate thinking. So I it's out of self-interest. In part, I really find thinking about it interesting so there is an impulse to share it with others (the interesting part). In part, I've figured out that by contemplating such matters makes me grasp my concepts and feelings about the world less. It leads my thinking to pacification. So I thought maybe it will also lead someone else thinking to the same result if they contemplate emptiness of phenomena. 

1. I wholeheartedly agree with that point. And it's indeed what the concept of emptiness points to, that there is no such thing as "empty space" or "just nothing", but, "The void is pregnant with infinite possibilities." It's the conceptual understanding of emptiness which helps us to unravel our grasping for something tangible and real. And indeed that's the question of physics. But one can marvel at that even outside of the physical perspective.
2. I haven't seen the blog you've mentioned, I'll check it out. I liked your examples. The concept of emptiness is exactly directed to our meaning making process. How does it help to contemplate that? If we set absolute meaning and expectation to our life we suffer. We turn nihilistic when we expect life to have intrinsic meaning with regard to our values and become disappointed when we are faced with the way things are. 
   In order to be free from that we have to question if meaning that was built really does have that intrinsic nature or it's just conventional. Contemplating emptiness helps us to disassemble our beliefs and release our absolute expectations not only on conceptual level but on the level of feeling. 
   It also helps us to be free from the nihilistic stance. As we take ourselves and our meaning making less seriously (in a good sense). We can see that our previously set intrinsic meaning was empty to begin with, so there is no reason to despair because of that. And by seeing that all meaning is conventional, we can let go grasping for sand castles and make the best of it.
3. I agree that these are all useful questions to ask. And I keep them in mind. Maybe, it doesn't transfer through the text. 

One more reason I wanted to share this is to start a conversation on emptiness (not necessarily between myself and other people, but for people just to stop for a moment and ponder this, like you did!) I think when we're contemplating something abstract, we're releasing our attention from purely pragmatic and material matters and enter some other space or mode of thinking which helps us to disentangle with our worries of everyday life. To put it simply we stop thinking about politics, wars, catastrophes, etc. and think about something entirely different. Which brings a release to thinking. 

I like another related Daoist concept of "worth of worthless" or "usefulness of useless knowledge" (reference to Abraham Flexner's article). If we only think about issues of the day or only about practical matters, our thinking is caught in the loop of worries and concerns. If we start and think about seemingly unrelated to anything matters, first, we relax as nothing is at stake (we can be silly if we like), and second, we might find solutions to our problems we couldn't have predicted. It serves as a link or a bridge between seemingly unrelated areas of our experience. Maybe I will develop this theme into another post or maybe LW is not the place for such reflection. 

Having said all this, I wanted it to be an open question and an exploration into emptiness and the self. What does emptiness mean? What do I really know? What is the ground of my experience? What does it mean to be empty of the self? Who am I? etc. Not "transferring profound truths". To start a reflection (as it worked in your case). Whether or not some people find it interesting or useful that's for them to decide. I personally find contemplation over emptiness useful as it disentangles my thinking from everyday matters and helps to release stress. But it also has a light touch to it which is not unlike John Cage's piece 4'33. 

And (probably most importantly) to highlight that having an insight into emptiness may open the door to awakening. 

To finish this with another Wittgenstein quote: 

6.54 My propositions serve as elucidations in the following way: anyone who understands me eventually recognizes them as nonsensical, when he has used them—as steps—to climb beyond them. (He must, so to speak, throw away the ladder after he has climbed up it.)

Sorry for the disappointment. But you've discovered something - the emptiness of content! It is not sarcasm. Fundamentally, even the disappointment is empty as it's dependent on the expectation (but to get this far one has to contemplate deeply). Any phenomenon - external or internal - can be approached this way. That's the payload. 

EDIT: It's not a cheap trick! One can think of it this way. First, there is a conceptual understanding of emptiness (you've heard of it somewhere and have discovered conceptual emptiness of constructs). Second phase is to apply it on the perceptual level (as in the example with the disappointment, one can actually be free from it but it's an advanced level of insight into emptiness). And the final phase is to understand the emptiness of intrinsic meaning we set to our life, or our "intrinsic" expectation from life. The last phase is non-trivial. If one gets insight into it, one awakens. In this way our "intrinsic" disappointment with life disappears.

Thanks for the compliment! :-) But I'm not a philosopher. 

I look at it differently. Something has caught your attention. And if the text has made you stop and ponder for at least a tiny moment on any word/question/relation, then it's played its function - to gleam at things from a different perspective. 

It's like in the parable about the blind men and an elephant. We look at life from different perspectives or different levels of abstraction. What we compress from it turns into our understanding. If we like, we can operate at different levels of abstraction constructively in complementary fashion. Every kind of knowledge contains in itself potential for some understanding (even if it's negative). Not always and not everything can be formalized and reduced to simple logical rules without contradictions (think about Gödel's theorems). And there was no intention to do that. 

Here the intention was to share something that I find to be interesting and which may lead other people to reflect. What concerns my skill to do that - that's entirely different point. And understanding is a little miracle when it happens, but it is not a necessity. 

Thank you for your kindness and time! 

• Do you have a teacher?

  No. It's impossible to find one where I am. 

• What type of meditation do you do / have you done?

  Currently: self-inquiry practice, sometimes meditation on breathing. Previously: meditation on breathing, mindfulness meditation. 

• How long have you been doing it for (both time per sit and calendar time)?

  Since 2013. 1-3hr per day (no more than 1hr per sit).

• What books and other material have you read?

  Too many to mention. I've read the first two books from your list. I will list books that affected me deeply and directed/direct the practice: 
  - Ramana Maharshi: Who am I?, Talks with Sri Ramana Maharshi, The Collected Works, Day by Day with Bhagavan, etc., all books by him or about him. 
  - Philip Kapleau, The Three Pillars of Zen. Bassui's letters are all gold!
  - Gary Weber: Happiness Beyond Thought, Dancing Beyond Thought, Evolving Beyond Thought.
  - Krishnamurti Jiddu: Commentaries on Living, Krishnamurti to Himself, Krishnamurti's Journal, A Wholly Different Way of Living, etc., many books and videos.
  - Chögyam Trungpa: The Sanity We Are Born With, Meditation in Action, The Sacred Path of the Warrior, Smile at Fear, The Mishap Lineage: Transforming Confusion into Wisdom, etc., many entry books on basic sitting meditation and Dharma in simple terms. 
  - Nisargadatta Maharaj: I am That. 
  - Nāgārjuna: The Ornament of Reason (translation by Mabja Jangchub Tsondru), The Fundamental Wisdom of the Middle Way (translation by Jay Garfield), Letter to a Friend, Precious Garland. Used for reflection. 
  - Longchenpa: The Precious Treasury of The Way of Abiding, The Precious Treasury of the Basic Space of Phenomena, The Precious Treasury of Pith Instructions, etc. 
  - Alfred Korzybski: Science and Sanity, Manhood of Humanity, etc. Used for reflection. 
  - Alexander Piatigorsky: The Buddhist Philosophy of Thought, Symbol and Consciousness, etc. Used for reflection. 
  - Henepola Gunaratana: Mindfulness in Plain English. 

• What have you tried that you like and dislike?
  - mindfulness meditation^[1]: it worked in the beginning, was reaching Access Concentration, but now I lose interest quickly; 
  - repetition of mantras and looking for the source where they come from: worked during really dark times, but now feels off;
  - chanting: working but I take it more like a plaything;
  - meditation on breathing^[2]: it works leading to Access Concentration, ok with it; 
  - self-inquiry^[3]: grappling with it, previously led to mystical experiences, sometimes hits "the sweet spot" and Access Concentration, can do it while walking, waiting in queues, etc, it's my preferred practice as I deeply resonate with the question;
  - relaxing into awareness^[4]: it does miracles when it works, but it's not consistent and depends on external factors (like the state of the mind and weather);
  - just sitting (shikantaza): as a rule it doesn't work but occasionally it hits "the sweet spot", i.e. Access Concentration;
  - counting breaths^[5]: it works and leads to Access Concentration;
  - kirtan kriya^[6]: it works for short periods of time (like 15 minutes), gets to Access Concentration quickly;

   

• Set up a video call with this teacher. He is legit. You can set up a video call with me too, if you like.

  Thank you for your kindness! I'll keep that in mind. 

• Don't attempt to consciously shut down your DMN. Don't even worry about it. Getting into a state where the DMN is shut down by default temporarily feels like a side effect of concentration. Changing the DMN's default state comes from insight and/or mindful living practice, not mere concentration. Even people with normal DMNs feel like thoughts are running galore when they begin meditation. This is normal.

  I have a medical condition which I'm uncomfortable of sharing but which suggests that the DMN is overly active in my case. In practice it means more self-rumination and less clarity. 

• Did a teacher you respect give you the koan? If not, I recommend against koan practice entirely. (If you like koan practice and feel koan practice is working for you, then disregard this bullet point.)

  Yes, Gary Weber in personal correspondence suggested me to continue with the koan/self-inquiry and also suggested a mantra/breathing practice to switch gears. 

• If you have a mystic experience and then it goes away due to something like "I could not stay there long as ego reappeared", that isn't a failure of the practice. It actually means things are going correctly, because it is giving you insight into what your ego is and how it operates.

• If possible, find a local community of good practitioners who do lots of sitting (not too many trappings of religion) and who don't ring any culty alarm bells. They can be any denomination.

  It's problematic where I live. 

   

  Finally, a warning: This meditation stuff can make sensory overload worse [for months] before it makes it better.

  Yeah, that point is loud and clear to me. 

1. ^{^}

   Simply coming back to awareness when noticing thoughts. 

2. ^{^}

   Coming back to breathing when noticing thoughts. 

3. ^{^}

   "As each thought arises, one should inquire with diligence, "To whom has this thought arisen?" The answer that would emerge would be "to me". Thereupon if one inquires "Who am I?", the mind will go back to its source; and the thought that arose will become quiescent. With repeated practice in this manner, the mind will develop the skill to stay in its source." / Ramana Maharshi, Who am I?

4. ^{^}

   Simply letting go all strife and practices and abiding in awareness. I have distilled it from Longchenpa and Dzogchen. 

5. ^{^}

   Counting breaths every inhale and exhale, or just exhales. 

6. ^{^}

   Kirtan Kriya by Gary Weber.

Thanks for your post! Do you have any recommendations on practice which would lead to Stream Entry? Or some "one-shot" material. Anything you may find of value. 

I'm working on a koan and have similar issues with sensory overload. It makes life sometimes unbearable. The practice led to some results in the past. I've probably had a kenshō in which everything including the subject-object duality has disappeared into one dark luminous field of awareness which was a manifestation of stillness and care, but I could not stay there long as ego reappeared. And I could not repeat the experience since then. Had a couple more "no self" experiences which lasted from 5 minutes to an hour. But could not replicate them either. So I think the practice has become stalled. It probably even become worse as thoughts run galore (I think it's connected with overly active DMN in my case). 

So I'm on crossroads thinking whether I should keep going with the koan no matter what (and there is a strong tendency to do that) or try some other stuff (tried basic breathing meditation and it seemed to work). I've verified that it all is not mumbo-jumbo stuff, the problem is how to shut down the DMN and reach that state permanently. 

In addition, how do you recognize that you've reached Access Concentration? In my case, I think when thoughts practically stop (which happens rarely) and there is a feeling of serenity and equanimity that's basically it. But I could not reach it each time I sit. Would you please comment on that and how do you generally reach it?