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 ?
Veraart, "Position, size and luminosity of phosphenes generated by direct optic nerve stimulation," Vision Research, vol.
Another special case was a 15-year-old female with Takayasu arteritis who complained of amaurosis fugax and phosphenes (the symptoms occurred for 30 minutes when she was getting up and disappeared after she lied down), eye swelling, and tearing.
A local and "purely" cortical TMS application over the visual cortex was found to also induce phosphenes and, in fact, was used to measure the effects of tDCS on visual cortex excitability [3].
According to the literature, elementary visual symptoms either positive (flashes and phosphenes) or negative (scotoma, hemianopsia, and amaurosis) are usually considered due to the stimulation or inhibition of the primary visual cortex and optic radiation [20, 44, 45].
Binary coded words have been transmitted via internet from an emitter's brain located in India and equipped with an EEG cap allowing the real-time analysis of signals from cerebral activity, into a receptor's brain located in Strasbourg, who was stimulated by a robotized Transcranial Magnetic Stimulation system, triggering or not phosphenes (flashes of light), for de-coding the message.
- Acouphenes (sifflements auditifs) et des phosphenes (vision de points lumineux) - Vertiges.
Phosphenes and transient scotomas induced by magnetic stimulation of the occipital lobe: their topographic relationship.
Scientists call these lights you see with your eyes closed phosphenes. You see these phosphenes after you see something bright, or when you come into the light after being in a dark room like a movie theater or a mine shaft.
Patients see bursts of light called phosphenes and "not truly naturalist vision; says Raymond Iezzi, a clinician-scientist who performs retinal surgeries at Mayo Clinic in Rochester, Minnesota.
Images seen with eyes closed included phosphenes, geometric patterns (waves, stars, DNA-like structures, fractals), afterimages and, in one case, an image of a person.
Dr Lauren Ayton, from the Centre for Eye Research Australia said: "With the prototype the idea is to stimulate the retina to give little spots of light, which are called phosphenes, and so, with her implant, Di will be able to see a number of spots in different locations and will be able to see things like shapes and the edges of doorways and objects like that eventually."