Derealization

Derealisation is a state in which the outside world appears unreal, distant, flat, artificial or dreamlike, while reality testing generally remains preserved. It is an alteration of the sense of reality, not a single mechanism.

Neurobiological mechanisms

Derealisation has no single mechanism. Models converge on a disruption of integration between sensory regions, limbic regions and the prefrontal cortex. Several avenues are mentioned: stress and trauma, prefrontal hyperactivity combined with deep limbic inhibition; dissociation and NMDA antagonism, a rupture of perceptual integration; cannabis and CB1 modulation, of sensory gating and the feeling of presence; HPPD or post-psychedelic states, persistence of anomalies in sensory processing (mechanism unknown). The plate specifies that this is a multifactorial state, not reducible to a single pharmacological pathway.

Bayesian perceptual loop

Within the predictive framework, derealisation corresponds to a precision imbalance. The perceived world loses its density of reality when the internal model is no longer adjusted by priors and contextual signals (top-down) against ascending sensory data (bottom-up). Two modes are distinguished: an impoverished or rigid mode, where perception arrives but without the weight of the real (dampened signals); a contemplative or emptiness mode, where the predictive stance creates detachment, inference remaining but without adhesion or belief. Derealisation is not another world, but reality under another filter: it is often the world itself that is felt as distant and uninhabited.

Modal mapping of derealisation

The plate distinguishes several regimes. The transient mode (stress, fatigue, dehydration, overload): brief episode, spontaneous dissociation. The induced or modulated mode: psychedelics, cannabis, dissociatives, altered states, a strange sensitive mode, the dreamlike at a blurred distance. The chronic or pathological mode: depersonalisation and derealisation disorder, HPPD or other, persistence, suffering and possible decline. The ontological or emptiness mode: a perceived mode emptied of presence, at the border of meditative phenomenologies, even towards the mystical (a state of contemplation or emptiness). The plate stresses that one and the same phenomenological structure (contemplative insight) may be lived as pharmacological or as a clinical symptom.

Phenomenology

The functional consequences described: the world appears unreal, hazy, distant or like a stage set; a sensation of a barrier, a glass pane or separation from the environment; loss of emotional relief and the impression of a less alive world; alteration of time (slowing, strangeness, suspension); diminished presence, difficulty anchoring in the present; reality testing usually preserved, the subject knows that something is wrong. The plate gives examples of open-eye experiences: the world resembles a set or a film seen from afar; people and objects seem distant, a pane of glass or a fog; the impression of being behind glass; time appears slowed, frozen or unreal; everything seems empty, without emotional texture; the sensation of being in a dream, without really being elsewhere.

Harm reduction

The plate distinguishes duration and clinical status. Duration is variable: a transient episode (minutes to hours); post-substance (hours to days); after a bad experience, possible persistence; chronic forms (days, months, years). Clinical status is graded: a passing state, an induced altered state, or depersonalisation and derealisation disorder. The recommendations: for a brief episode, rest, hydration, bodily grounding; while under a substance, do not fight it, wait for the effect to end, a reassuring presence is helpful; for persistence or recurrence, medical or psychological consultation is recommended; an emergency in the case of a distress crisis, suicidal thoughts, severe confusion or psychotic symptoms. Derealisation is a state that is often transient and most often benign, but an established disorder remains treatable.

Sources

• Sierra, Simeon, Medford, work on depersonalisation and derealisation.
• Literature on dissociation and NMDA antagonism (ketamine and dissociative states).
• Work on cannabis, CB1 signalling and sensory gating.
• Research on HPPD and persistent anomalies of perceptual processing.
• The predictive coding and precision framework in perception (Seth, Friston, on inference and the sense of presence).