Phosphene

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phosphene

[′fäs‚fēn]
(psychology)
Sensation of spots of light in the visual field due to a stimulus other than light, such as pressure on the eyeball or an electrical stimulus to the retina or visual pathway.

Phosphene

 

a visual sensation that occurs in man without the action of light on the eyes.

Phosphenes may appear spontaneously in the dark, or they may be induced by mechanical pressure on closed eyes, by the chemical action of psychotropic agents on the central nervous system, or by the electrical excitation of the retina through electrodes placed on the temples. They can also be induced by direct electrical excitation of the visual centers of the cerebral cortex.

Phosphenes may be bluish, greenish, yellowish, or orange in color; their shapes are varied. When phosphenes are produced by excitation of the visual centers of the cerebral cortex, the subject ceases to see his surroundings and sees only light spots, which move with the eye movements. The excitation of adjacent regions of the cortex produce phosphenes of geometric and other shapes.

Phosphenes are not seen by persons blind from birth, but they may be induced in individuals who have become blind. Therefore, attempts are being made to create visual prostheses using artificial excitation of phosphenes. Phosphenes seen by a person in the presence of illumination sometimes blend with the images he sees of the real world, thereby creating visual illusions. Bright phosphenes may be a symptom of disease.

REFERENCES

Luriia, A. R. Vysshie korkovye funktsii cheloveka i ikh narusheniia pri lokal’nykh porazheniiakh mozga. Moscow, 1962.
Oster, G. “Fosfeny.” Nauka i zhizn, 1971, no. 4.
N. A. VALIUS
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References in periodicals archive ?
Patients report many kinds of TMS-induced phosphenes, but they don't generally mesh with descriptions of ball lightning.
In the early 1990s, intraoperative stimulation in patients with late-stage retinitis pigmentosa (RP) showed that phosphenes could be elicited from blind retinal areas long after photoreceptor degeneration [3].
Phosphenes can occur spontaneously as a result of visual deprivation, and can be provoked in a number of ways.
When the researchers used TMS on the visual cortex, it could make people see illusory spots of light called phosphenes.
The field of retinal prosthetics has greatly expanded since the first report of visual sensations or phosphenes being elicited with electrical stimulation [1-5].
In the central train station, on "Bizz Board" screens that usually feature trailers for upcoming films, Janssens presented Phosphenes (Fireflies), 1997/99, an image of two people pressing their fingertips to their eyelids, accompanied by a moving text proposing that viewers do the same in order to experience "colorful and luminous patterns.
And, if (5) isn't too out-there for you, it's ultimately of course not even actors we're espying, not even people: it's EM-propelled analog waves and ionized streams and rear-screen chemical reactions throwing off phosphenes in grids of dots not much more lifelike than Seurat's own impressionistic "statements" on perceptual illusion.
In an early stage of trance, subjects 'see' luminous, pulsating geometric forms known as entoptic phenomena, form constants or phosphenes (e.
If the top level is somewhere within the neck of the bottle, it is regarded as perfectly filled Aglet The metal or plastic-coated end of a shoelace Ferrule The metal band on the end of a pencil that holds the rubber in place Obdormition Numbness felt after pressure on a limb, such as sleeping on your arm so it falls asleep Peen The curved end of the hammer, opposite the flat hitting side Phosphenes The swirly lights seen when the eyes are closed tightly.
This type of entoptic phenomenon may also be classified as phosphenes (see later).
The most common adverse events were phosphenes and bradycardia, which occurred more frequently with ivabradine.
The elevated response is consistent with other evidence for a hyperneuronal response in migraine: (1) the threshold for phosphenes in response to transcranial magnetic stimulation of the occipital cortex is lower in migraineurs than in controls (64) (2) the visual evoked potential has a greater amplitude (e.