Samadhi

 A

The neurobiology of samādhi — a deep meditative absorption described in yoga, Buddhism, and other contemplative traditions — is an emerging area of neuroscience that attempts to understand how this state of profound concentration and awareness corresponds to measurable brain activity. While “samādhi” is a spiritual and experiential term, modern neuroimaging has begun to identify some of the neural correlates that may underlie it.

Let’s break this down carefully:

🧠 1. What 

Samādhi

 Refers To (Phenomenologically)

In classical yoga (e.g., Patañjali’s Yoga Sūtras), samādhi is the culmination of meditative practice, where the distinction between the meditator and the object of meditation dissolves.

It is characterized by:

• Complete absorption and stillness of the mind.
• Loss of self-referential processing (“ego dissolution”).
• Timeless awareness and equanimity.
• Cessation of discursive thought.

In neuroscience, this is often compared to the “nondual awareness” or “pure consciousness” states reported by advanced meditators.

⚡ 2. Neural Correlates Observed in Studies

a. 

Default Mode Network (DMN) Deactivation

• The DMN includes the medial prefrontal cortex, posterior cingulate cortex, and angular gyrus — areas active during self-referential thought.
• During deep meditation or samādhi-like states, fMRI and EEG studies show marked deactivation of the DMN.
• This correlates with the loss of self-awareness and nondual experience reported subjectively.

b. 

Increased Integration in Fronto-Parietal and Thalamo-Cortical Networks

• These networks support sustained attention and conscious awareness.
• EEG coherence increases between frontal and parietal electrodes during absorption, suggesting enhanced global integration.
• The thalamus, acting as a gatekeeper of sensory input, may filter out external stimuli, enabling inward absorption.

c. 

Altered Activity in the Insula and Anterior Cingulate Cortex (ACC)

• Both regions are key for interoception, emotional regulation, and metacognitive awareness.
• In samādhi, there is often increased insular activity, reflecting heightened bodily awareness without attachment.
• The ACC shows enhanced control of attention and suppression of distractions.

d. 

Gamma and Theta Oscillations

• Advanced meditators exhibit high-amplitude gamma synchrony (30–80 Hz), especially in frontal-parietal networks.
• Theta oscillations (4–8 Hz) are linked to deep internal focus and reduced sensory processing.
• The coexistence of slow (theta) and fast (gamma) rhythms may underlie the paradoxical experience of stillness with clarity.

🧬 3. Neurochemical and Autonomic Features

a. 

Neurotransmitters

• Serotonin (especially 5-HT2A receptor modulation) is linked to altered states of consciousness and ego dissolution.
• Dopamine activity in the mesolimbic system may relate to the bliss or ānanda aspect of samādhi.
• GABA and melatonin may increase during deep meditation, supporting calm, integrated brain states.

b. 

Autonomic Regulation

• Marked parasympathetic dominance (lower heart rate, increased heart-rate variability).
• Reduced metabolic rate (similar to deep rest but with preserved alertness).
• Increased coherence in heart–brain interactions, observed via HRV biofeedback and EEG.

🌌 4. Advanced Hypotheses

Some models suggest samādhi involves:

• Transient “re-tuning” of predictive coding circuits, reducing top-down conceptual processing, allowing raw awareness.
• Reorganization of cortical hierarchies, where sensory processing and self-modeling networks are momentarily “flattened.”
• Increased global metastability — the brain becomes both deeply stable (low noise) and highly integrated (high synchrony).

🧭 5. In Summary

Neurobiological Aspect	Samādhi Correlate
↓ Default Mode Network	Ego dissolution, nondual awareness
↑ Fronto-parietal coherence	Sustained attention, unity of experience
↑ Insula & ACC activity	Bodily awareness, emotional balance
↑ Gamma synchrony	Integrative conscious state
Parasympathetic dominance	Calm alertness
↓ Metabolic rate	Deep rest without sleep

🕉️ 6. Integrative View

From a contemplative neuroscience perspective, samādhi may represent a unique attractor state of consciousness — a regime where self-referential processing quiets, attention stabilizes, and brain networks achieve maximal coherence with minimal energy expenditure.

It’s less about “switching off” and more about harmonizing the brain’s dynamics into a highly ordered, low-entropy state.

Would you like me to include a diagram of the neural networks involved in samādhi (e.g., showing DMN suppression and fronto-parietal integration)?