Visual release hallucinations, also known as Charles Bonnet syndrome (CBS), is the experience of complex visual hallucinations in a person with partial or severe blindness. First described by Charles Bonnet in 1760, it was first introduced into English-speaking psychiatry in 1982. Signs and symptoms Mentally healthy people with significant vision loss may have vivid
Sense of direction is the ability to know one’s location and perform wayfinding. It is related to cognitive maps, spatial awareness, and spatial cognition. Sense of direction can be impaired by brain damage, such as in the case of topographical disorientation. Humans create spatial maps whenever they go somewhere. Neurons called place cells inside the
Sensory processing is the process that organizes sensation from one’s own body and the environment, thus making it possible to use the body effectively within the environment. Specifically, it deals with how the brain processes multiple sensory modality inputs, such as proprioception, vision, auditory system, tactile, olfactory, vestibular system, interoception, and taste into usable functional
Example of how visual, auditory and somatosensory information merge into multisensory integration representation in the superior colliculus Sensory processing disorder (SPD; also known as sensory integration dysfunction) is a condition that exists when multisensory integration is not adequately processed in order to provide appropriate responses to the demands of the environment. The senses provide
How someone with synesthesia might perceive certain letters and numbers. Synesthetes see characters just as others do (in whichever color actually displayed) but may simultaneously perceive colors as associated with or evoked by each one. Synesthesia (also spelled synæsthesia or synaesthesia; from the Ancient Greek σύν syn, “together”, and αἴσθησις aisthēsis, “sensation”) is a
My eyes at the moment of the apparitions by August Natterer, a German artist who created many drawings of his hallucinations. A hallucination is a perception in the absence of external stimulus that has qualities of real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. They are
The ganzfeld effect (from German for “complete field”), or perceptual deprivation, is a phenomenon of perception caused by exposure to an unstructured, uniform stimulation field. The effect is the result of the brain amplifying neural noise in order to look for the missing visual signals. The noise is interpreted in the higher visual cortex, and
Anomalous experiences, such as so-called benign hallucinations, may occur in a person in a state of good mental and physical health, even in the apparent absence of a transient trigger factor such as fatigue, intoxication or sensory deprivation. The evidence for this statement has been accumulating for more than a century. Studies of benign hallucinatory
Hypnagogia is the experience of the transitional state from wakefulness to sleep in humans: the hypnagogic state of consciousness, during the onset of sleep. Mental phenomena that occur during this “threshold consciousness” phase include lucid thought, lucid dreaming, hallucinations, and sleep paralysis. Definitions Sometimes the word hypnagogia is used in a restricted sense to
A hypnic jerk, hypnagogic jerk, sleep start, sleep twitch or night start is an involuntary twitch which occurs just as a person is beginning to fall asleep, often causing them to awaken suddenly for a moment. Physically, hypnic jerks resemble the “jump” experienced by a person when startled, sometimes accompanied by a falling sensation. Hypnic
A lucid dream is a dream during which the dreamer is aware of dreaming. During lucid dreaming, the dreamer may be able to exert some degree of control over the dream characters, narrative, and environment. Etymology The term ‘lucid dream’ was coined by Dutch author and psychiatrist Frederik van Eeden in his 1913 article
The microwave auditory effect, also known as the microwave hearing effect or the Frey effect, consists of audible clicks (or, with speech modulation, spoken words) induced by pulsed/modulated microwave frequencies. The clicks are generated directly inside the human head without the need of any receiving electronic device. The effect was first reported by persons working
Sensory deprivation or perceptual isolation is the deliberate reduction or removal of stimuli from one or more of the senses. Simple devices such as blindfolds or hoods and earmuffs can cut off sight and hearing, while more complex devices can also cut off the sense of smell, touch, taste, thermoception (heat-sense), and ‘gravity’. Sensory deprivation
An approximation of Eigengrau vs. the black color Eigengrau (German: “intrinsic gray”, lit. “own gray”; pronounced [ˈʔaɪ̯gn̩ˌgʁaʊ̯]), also called Eigenlicht (Dutch and German: “own light”), dark light, or brain gray, is the uniform dark gray background that many people report seeing in the absence of light. The term Eigenlicht dates back to the nineteenth
Dark retreat (Wylie: mun mtshams) refers to advanced practices in the Taoism, Dzogchen lineages of the Nyingmapa, Bönpo, other schools of Tibetan Buddhism. A dark retreat is a solo retreat in a space that is completely absent of light. Because there is no optical stimulation, one can experience “prisoner’s cinema”, commonly known as the lights.
A phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye. The word phosphene comes from the Greek words phos (light) and phainein (to show). Phosphenes that are induced by movement or sound may be associated with optic neuritis. Artist’s depiction of mechanical phosphene Phosphenes can
Closed-eye hallucinations and closed-eye visualizations (CEV) are a distinct class of hallucination. These types of hallucinations generally only occur when one’s eyes are closed or when one is in a darkened room. They can be a form of phosphene. Some people report closed-eye hallucinations under the influence of psychedelics. These are reportedly of a different
A psychedelic experience (or ‘trip’) is a temporary altered state of consciousness induced by the consumption of psychedelic drugs (such as LSD, mescaline, psilocybin, 2C-I, DOM, AMT, DMT, and 5-MeO-DMT). For example, the term acid trip refers to psychedelic experiences brought on by the use of LSD. The term “psychedelic” derives from Greek words meaning
Simulated reality is the hypothesis that reality could be simulated — for example by quantum computer simulation — to a degree indistinguishable from “true” reality. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation. This is quite different from the current, technologically achievable concept
Parosmia (from the Greek παρά pará and ὀσμή osmḗ), also known as troposmia (Gk.) or cacosmia (Gk.), is an olfactory dysfunction that is characterized by the inability of the brain to properly identify an odor’s “natural” smell. What happens instead, is that the natural odor is transcribed into what is most often described as an
Sensory substitution is a change of the characteristics of one sensory modality into stimuli of another sensory modality. A sensory substitution system consists of three parts: a sensor, a coupling system, and a stimulator. The sensor records stimuli and gives them to a coupling system which interprets these signals and transmits them to a stimulator.
The McCollough effect is a phenomenon of human visual perception in which colorless gratings appear colored contingent on the orientation of the gratings. It is an aftereffect requiring a period of induction to produce it. For example, if someone alternately looks at a red horizontal grating and a green vertical grating for a few minutes
Perceptual psychology is a subfield of cognitive psychology that is concerned specifically with the pre-conscious innate aspects of the human cognitive system: perception. Perceptual psychology is a branch of cognitive psychology dealing with mental processes that we use in everyday living. Any time you solve a problem, make a decision or make a memory you
Sensory neuroscience is a subfield of neuroscience which explores the anatomy and physiology of neurons that are part of sensory systems such as vision, hearing, and olfaction. Neurons in sensory regions of the brain respond to stimuli by firing one or more nerve impulses (action potentials) following stimulus presentation. How is information about the outside