From a clinical and neuroscientific standpoint, depersonalization-derealization disorder (DPDRD) is increasingly understood as involving profound disruptions in multisensory integration, emotion regulation, and self-referential processing, often in response to overwhelming stress, trauma, or chronic emotional dissonance.

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1. Multisensory Disintegration & Cortical Decoupling

At its core, DPDRD reflects a breakdown in the integration of interoceptive, proprioceptive, and exteroceptive data. Normally, these sources of information are woven into a coherent sense of bodily and situational self—an embodied first-person perspective. In DPDRD:

• Activity in posterior insula and somatosensory cortex may be diminished, reducing the felt sense of being in a body.

• Temporoparietal junction (TPJ), a hub for integrating body-relevant information, may be overactive or misfiring, generating out-of-body sensations or a detached observer stance.

• There is decoupling between limbic (emotion-generating) and prefrontal (evaluative) regions—particularly between the amygdala and ventromedial prefrontal cortex (vmPFC)—resulting in a dampened affective response and a surreal, "flat" world experience.

This accounts for the eerie hyper-clarity without feeling, where the world seems vivid but hollow, much like your "bell that removes sound."

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2. Default Mode Network (DMN) Disruptions

The Default Mode Network—a set of brain regions active during self-referential thought (e.g., medial prefrontal cortex, posterior cingulate, precuneus)—plays a key role in maintaining the narrative self. In DPDRD:

• Some fMRI studies show hyperactivity in the DMN, which may cause excessive internal monitoring and ruminative self-observation—"being too aware of awareness."

• Other studies suggest hypoconnectivity or inefficient switching between the DMN and salience network (responsible for detecting what’s relevant), which may explain the overwhelmed-yet-detached feeling: everything is salient, yet nothing can be acted upon.

This also mirrors your insight about being “flabbergasted” by everything—perceiving too much significance with no embodied foothold.

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3. Polyvagal Theory and the Freeze Response

Stephen Porges’ polyvagal theory suggests that when fight or flight isn’t possible, the body shifts into a dorsal vagal (freeze/shutdown) state—a kind of biological dissociation. In this state:

• Heart rate slows, digestion pauses, pain perception dulls.

• There’s a withdrawal from social engagement systems (via vagal brake).

• The person may feel deadened, robotic, or ghostlike.

This maps well to the notion of escaping when there is no escape—the body shuts down to survive the unendurable. It’s not a psychological decision but a neurophysiological fallback.

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4. Neurochemical Factors

• Cortisol dysregulation (from chronic stress) alters hippocampal and amygdala functioning, interfering with memory integration and emotional salience.

• Low levels of serotonin, endogenous opioids, or glutamate may contribute to the numbing, detached quality of the experience.

• Ketamine studies suggest that NMDA receptor dysfunction may induce dissociative states, indicating a role for glutamatergic dysregulation.

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5. Predictive Coding & Bayesian Brain Models

Karl Friston’s free energy principle and related models suggest that the brain constantly predicts sensory input and updates based on error. In DPDRD:

• The brain may begin to mistrust bottom-up signals (from the body, from the senses) and overweight top-down predictions.

• This leads to a sense that nothing is quite real or inhabited—reality is “modeled,” not lived.

This creates a suspended self-model: the self is representationally present but sensorially absent, like a ghost in a simulated machine.

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Summary:

Domain	Explanation of DPDRD
Multisensory processing	Disintegration of interoceptive, proprioceptive, and exteroceptive signals.
Cortical networks	TPJ overactivity, DMN/limbic decoupling, vmPFC hypoactivity.
Polyvagal system	Freeze/shutdown response due to unresolved threat.
Neurochemistry	Serotonergic and glutamatergic dysregulation.
Predictive coding	Overweighted priors suppress embodied presence; the model replaces reality.