An internal hallucination is the perception of a visual hallucination that exclusively occurs within an imagined environment which can typically only be viewed with closed eyes   , similar to those found within dreams.    This is in stark contrast to external hallucinations, which display themselves seamlessly into the external environment as if they were actually happening. At lower levels, internal hallucinations begin with imagery on the back of a person's eyelids which do not take up the entirety of one's visual field and are distinct from their background. These can be described as spontaneous moving or still images of scenes, concepts, places, and anything one could imagine. The imagery is manifested in varying levels of realism, ranging from ill-defined and cartoon-like in nature to wholly realistic. They rarely hold their form for more than a few seconds before fading or shifting into another image. It is worth noting that this level of intensity occurs in a highly similar manner to that of hypnagogia, the state between sleep and wakefulness. At higher levels, internal hallucinations become increasingly elaborate as they eventually become all-encompassing, fully-fledged 3D scenes which surround the person in a similar manner to that of dreams. This can create the feeling that one has "broken-through" into another reality. The things which occur within this perceived alternate reality can be anything but fall under common archetypes, such as contact with autonomous entities alongside a wide variety of imagined landscapes, and scenarios. This effect is capable of manifesting itself across the 5 different levels of intensity described below:
- Enhancement of mental visualization - At the lowest level internal hallucinations can be defined as a distinct enhancement of mental visualisation that a person drifts into when daydreaming or using their imagination. It can be described as a short-term detachment from one’s immediate surroundings, during which a person’s contact with reality is blurred and partially substituted by an ill-defined fantasy. The details of this internal visualisation are slightly spontaneous or autonomous in nature but are mostly controlled by the content of one’s current thought stream.
- Partially defined imagery - At this level, internal hallucinations consist of partially defined, blurred, and faded imagery within a person’s visual field.
- Fully defined imagery - At this level, the vividness and intensity increases in a fashion which renders the imagery seen within one’s visual field as fully defined and realistic in its appearance.
- Partially defined immersion - At this level, the vividness, scope, and intensity of the hallucinations become all-encompassing in a way which begins to display momentary flashes of scenes which surround the person in an immersive environment in a similar fashion to that of a vague dream. Although all-encompassing, they are often blurred or transparent in appearance, and a person’s physical body still feels as if it is partially connected to the real world.
- Fully defined immersion - At the highest level, the internal hallucinations further increase to become all-encompassing in a manner which displays long-lasting scenes which surround the person with an explorable and fully immersive environment which is similar to that of a dream. This occurs in a fashion which is entirely realistic, detailed, and highly vivid in its appearance. It typically also occurs alongside relevant auditory and tactile hallucinations, as well as the sensation that a person has become completely disconnected from their physical body.
The specific differences between each potential style of internal hallucination can be broken down into the following variations:
- Lucid vs. Delirious - Hallucinatory states can maintain a consistent level of awareness throughout them regarding the fact that none of these events are actually happening and that the current situation is simply a result of drug-induced hallucination. In contrast to this, hallucinations can also become completely believable, no matter how nonsensical they may be, in the same way, that one does not have any problem accepting “absurd” and non-linear plots within ones dreams.
- Interactive vs. Fixed – Hallucinatory states can either present themselves as completely separate in a manner, that is similar to watching a video play out in front of one’s field of vision, or they can be completely interactive. For example, conversing with autonomous entities or interacting with imagined objects in a fashion similar to lucid dreaming is entirely possible.
- New experiences vs. Memory replays – Regarding their subject matter, hallucinations can either be entirely new experiences or they can follow themes of normal, everyday situations and a replaying of specific memories.
- Controllable vs. Autonomous – Imagery and hallucinations can be partially to completely controllable. This can be described as the content of their appearance always seeming to perfectly follow and fit the general topic and subject matter of one’s current thought stream, with varying levels of partial to absolute control. In contrast, autonomous hallucinations are completely spontaneous in their subject matter and entirely uncontrollable.
- Geometry-based vs. Solid – Hallucinations can be comprised of condensed psychedelic geometry or they can appear to be made from realistic materials.
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