Body Dissolution / Depersonalization

Body Dissolution — the specific somatic component of the broader depersonalisation experience — is the phenomenological experience in which one's ordinary sense of the body as a bounded, integrated physical structure begins to lose its edges. Limbs may seem to extend to the horizon, or to lose their attachment to the trunk; the boundary between the body and the surrounding space becomes negotiable; the sense of physical location within the body (the proprioceptive self) softens or disappears entirely.

Distinct from depersonalisation proper (the loss of the sense that one is one's ordinary self) and from derealisation (the sense that the external world has lost its reality), body dissolution specifically concerns the felt-sense architecture of embodiment. In its lighter forms it is one of the most common early experiences reported with psychedelics, dissociatives, deep meditation, and sensory deprivation: a heaviness or lightness of the limbs, a sense of the body 'melting' into the surface it rests on, a felt spreading of the body's boundary into the surrounding air. In its deeper forms — most consistently reported on ketamine, DMT, and high-dose psilocybin — the sense of having a body at all becomes optional: awareness continues without any felt-sense location within a physical structure.

Body dissolution shares much of its phenomenology with the out-of-body experience (OBE) reported in the near-death, sleep-paralysis, and specific meditative-practice literatures. The Buddhist rūpa-loka (form-realm) versus arūpa-loka (formless-realm) meditative absorptions describe a similar progressive dissolution of the sense of embodiment; the Tibetan phowa practices work explicitly with the same threshold. Contemporary neurophenomenology has correlated the state with disruption of the temporoparietal junction and the insular cortex — the same regions implicated in ordinary bodily self-awareness — while remaining, as usual, agnostic about the specifically first-person quality of the experience.

Experiencers commonly report that a first significant body dissolution is disorienting, sometimes acutely so; that repeat encounters produce a distinctively different relationship with the body — an appreciation of it as a temporarily-inhabited structure rather than a fixed identity; and that the experience has practical value in reducing certain forms of chronic body-based anxiety, particularly those related to illness, aging, and mortality.

Sources:
PsychonautWiki — Physical disconnection
Wikipedia — Depersonalization