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Coming home, psychedelics, Bayesian brain: neuroscience explains "the return to one"

I once had a deep mystic Ayahuasca experience including the often-described feeling of "coming home". The overall phenomenology was identical to what in Tibetan Buddhism is described as "mirror Mind", I learned later.

This feeling is a component of the standard mystic experience typology. It is a deep feeling of oneness, awe, gratitude, and peace. It is suffused with the valence of truth.

In fact, it was utterly "spiritual". My understanding then of "spiritual" was "filled with weird beliefs", so I could not have been more surprised. I have since changed a little.

The Bayesian Brain theory

However, I am also a scientific mind..(..fake it, Till, you make it) , so eventually, I landed with the Bayesian brain (predictive processing) theory for a scientific explanation.

(AI content) The Bayesian brain theory proposes that the brain works by constantly making predictions and then updating its beliefs based on new sensory information. It views the brain as a probability machine that aims to construct the most accurate model of the world given the data available."

Relevant terms are prediction (model), prediction error, beliefs (priors)

Find a full textual explanation of the Bayesian brain theory with examples in nonscientific terms is here.

A more advanced good visual introduction to the theory is in Shamil Chandaria´s Youtube presentation "The Bayesian Brain and Meditation". Chandaria comes from Google AI, is a founder, is a neuroscientist, and knows his way around meditation and psychedelics.

Mapping the Bayesian brain to mystic states helped me with mapping predictive processing to the mystic feeling of coming home. The entire conversation is here, and below are the relevant extracts.

Before turning to that topic, I had asked around the Tibetan Buddhist concept of "rigpa" (the "space of awareness" in which all experience appears). You may or may not be aware of this awareness...

Then, I investigated issues around Bernardo Kastrup´s analytical idealism and his theory of " all encompassing consciousness, prior to mind and matter, dissociating itself into many parts".

Then I asked for spiritual traditions having a similar concept, where a "one" separates into "many", where the many can re-unite with the one, or actually remain the one without knowing it ( Advaita, Mahayana Buddhism etc) These traditions are often summarised as the "perennial philosophy" (Aldous Huxley).

Then I asked how neuroscience could explain this positive valence of "coming home to one-ness/unity" for all these traditions and for psychedelics.

Mapping "coming home" to the Bayesian brain

(Tip: Again, In order to comprehend the reply, it is really useful to listen to Shamil Chandaria first. Note that the presentation is about meditation, but Chandaria applies the concept to psychedelics too).

My question, based on my own experience:

Mystic experiences (such as religious or psychedelic peak experiences) typically include the feeling of "coming home", like a "re-cognition" of the primal unity described in those spiritual or philosophical traditions. How could this feeling of "coming home" be explained in the light of neuroscience, in particular in the light of the predictive processing (or Bayesian brain) hypothesis?

Claude´s reply

That's an insightful question. The feeling of "coming home" or re-cognizing primordial unity in mystical experiences is intriguing from a neuroscience lens. Here are a few ways it could be interpreted through the predictive processing/Bayesian brain hypothesis:

  • Reduced prediction error - The unified state may have a low level of prediction error between top-down priors and bottom-up signals, creating a sense of coherence/at-homeness.

  • Alignment with higher priors - Unified consciousness may represent very high-level abstract priors that align with the subjective experience, giving recognition/familiarity.

  • Relaxed precision weighting - The sense of at-homeness could come from reduced precision weighting of prediction errors, accepting the moment as it unfolds.

  • Subsumption of self-model - The small self-model subsides into a much larger consciousness model, creating a homecoming to a broader identity.

  • Enhanced model evidence - Rich sensory-semantic inputs during unity states provide overwhelming Bayesian evidence for higher consciousness models.

  • Pruning of competing models - Alternative models of reality are pruned away, leaving only the expansive unity model, which resonates as truth.

  • Minimal uncertainty - With sensory data fully accounted for by the unitary model, subjective uncertainty plummets, giving certainty of "coming home".

  • Reinforcement learning - The bliss of unity reinforces & stabilizes the higher predictive model, giving recurrent recognition upon later re-visits.

So in summary, the Bayesian brain offers several ways to interpret the sense of familiarity, truth and homecoming that accompanies experiences of mystical unity. But first-person subjective experiences may always exceed computational modeling.


My dialogue with

Shamil Chandaria, "The Bayesian brain and meditation"

Amit Seth, "The Neuroscience of Consciousness"

A thought on...

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