Digital Media Concepts/Phosphenes
A phosphene is a natural phenomenon characterized as seeing a ring or spot of light produced by a stimulus other than light. The word phosphene has it's origins in the late 19th century derived from the Greek words phōs 'light' and phainein 'to show.' Phosphenes can be viewed most often when one exerts gentle pressure to the eyelids, right after looking into a bright light, or when one finds themselves inside of a dark room. In such cases, one often sees disjointed patterns of colorful 'lights' in their vision. Phosphenes themselves are not actually light, but a kind of visual experience generated in the absence of light.
Biophotons: Human Bioluminescence edit
These 'lights' which are generated are cells within the eyes that release biological light particles are called biophotons. According to neuroscientist Istvan Bokkon, these biophotons are a form of natural bioluminescence much like the kind found in fireflies and other glowing organisms. The atoms in a person's eyes are constantly giving off and absorbing photons and so they are indistinguishable from biophotons within the eyes or outside light entering into the eye. Light passing into the retina is transformed and transmitted by photoreceptor cells as electrical signals which pass through the optic nerve and to the visual cortex of the brain. Based on the information received from the eyes, the brain is able to reconstruct a visible image either of the outside world or of phosphenes. Because different atoms and molecules give off photons of varied wavelengths, there is an abundance of differently colored phosphenes. Also, depending upon which part of either the retina or brain phosphenes are created, it can result in different geometric patterns from colorful speckle patterns to checkerboards.
There are numerous ways to induce phosphenes including mechanical stimulation, electromagnetic stimulation, sound triggers, and drug induction. Other causes for the generation of phosphenes are numerous medical conditions including multiple sclerosis and optic neuritis. The reason as to why phosphenes exist remnains somewhat of a mystery, although it is commonly believed by some that they are related to certain mystical visions in religion. In the realm of science, there are those who believe that the patterns of phosphenes can reveal the structure of a person's eyes and even serve as a kind of map of someone's brain. Research on the subject of phosphenes is extensive including a variety of different tests related to electromagnetic stimulation, the relationship with certain drugs and medications, and the cellular mechanisms involved in generating phosphenes in connection with certain diseases.
Mechanical Stimulation edit
The easiest way in which phosphenes can be generated is through mechanical stimulation, or by applying force to the eyes. When one closes their eyes and gently presses on the eyelids, it results in an excess generation of biophotons that produce stunning visuals. Any form of pressure will cause this emission of biophotons including sneezing very hard, experiencing a forceful blow to the head, or standing up too fast which causes a sudden drop in blood pressure. These so-called 'pressure phosphenes' are often referred to as 'seeing stars.' Studies reveal that such phosphenes are more easily produced in children than in adults. Usually, once children reach adolescence, it is considerably harder to conjure up phosphenes, although the reason as to why remains unclear.
The phosphenes generated through mechanical means are usually characterized as large spots that are blue, green, a pastel red, or yellow. Other common occurrences include darkening of the vision, a kind of fuzzy 'static', and wispy 'clouds' floating across the field of vision.
Electromagnetic Stimulation edit
The second way in which phosphenes are induced is through the use of electromagnetism. This method involves the use of electromagnetic signals, applied to regions of the visual cortex to illicit certain responses that generates phosphenes. In the 1950's, German scientist Max Knoll employed the use of an electronic probe when conducting his experiments on phosphene research. Using this method, he was able to successfully categorize phosphenes into 15 different groups based on shape after a test was conducted on over 1,000 patients. He concluded this after probing experimentally in different parts of the visual cortex, stumbling across the fact that very specific patterns appeared in different regions. Next to electromagnetic stimulation is a method known as TMS, or Transcranial Magnetic Stimulation. This way of generating phosphenes is considerably less invasive, and involves changing the magnetic fields around a person's brain creating an electric current. This electric current serves to stimulate the brain, specifically the visual cortex, resulting in a generation of biophotons. Studies have revealed that through the use of electromagnetic stimulation, phosphenes can be generated not only in perfectly healthy people, but blind patients as well. Those who have lost their vision to illness or injury do not lose all visual function. With the use of electromagnetism, it is possible to generate phosphenes. With this in mind, scientists hope to somehow use this knowledge to invent technology that could essentially restore sight.
Studies have revealed that certain frequencies of sound have been able to produce phosphenes. An experiment taken from the scientific journal Experimental Brain Research showed scientists applying sTMS to patients' occipital cortex in order to induce a kind of 'phosphene illusion.' The results showed that auditory stimuli played a part in early visual processing and could essentially change the way in which a person experiences 'conscious visual experiences.' Other research has led people to believe that there is a close correlation between sound-generated phosphenes and those who have some sort of optic defect such as optic neuritis. In an article put out by the American Academy of Neurology in 1979, they reported that those who have some sort of optic impairment observed that they were able to see phosphenes when they heard sounds. They concluded that "under conditions of altered excitability and visual deafferentation of the brain, cells capable of responding to both visual and auditory stimuli become hyperresponsive to sounds." Meaning that when the connections between nerve cells have been interrupted or destroyed, those which can still respond to visual and auditory stimuli become especially sensitive to sound. The phosphenes which were generated in these experiments were not particularly significant or dramatic, but enough to raise interest. Typically, it was a mere flash of light, or a sort of dull static. Interestingly enough, it was also discovered that certain frequencies of sound played a part in the kinds of phosphenes which one saw. For instance, sounds under the category of white noise.
Drug Induced edit
The generation of phosphenes is perhaps the most common side effect in the majority of clinical medications, especially stimulants, depressants, heart rate-lowering prescriptions, and hallucinogens such as LSD. Oddly enough, it has been observed that different pharmaceutical agencies will evoke different phosphene behavior based on the part of the brain which they stimulate. Colors, patterns, the speed at which they move across one's vision, etc. One drug in particular has raised the heads of scientific researchers: the heart rate-lowering medication known as ivabradine.
Ivabradine is an agent that works to lower a person's heart rate by restricting the hyperpolarization currents in cardiac node cells. Meaning that it inhibits a cell's ability to perform a task at a quicker rate, essentially slowing down cell function. During a clinical study, it was reported that 14.5% of patients reported seeing phosphenes during treatment. The hypothesis is that just as ivabradine interacts with cardiac node cells (If), it also restricts the hyperpolarization of retinal node cells (Ih) resulting in the emission of phosphenes.
Medical Conditions edit
Suzanne Carr, the author of the book Entopic Phenomena writes about a list of about thirteen known medical conditions which phosphenes are present. These include: falling asleep and waking up, insulin hypoglycemia, epilepsy, advanced syphilis, photostimulation, crystal gazing, drug intoxications, dizziness, fever delirium, psychotic episodes, sensory deprivation, electrical stimulation, and migraine headaches. Phosphenes are known to occur under these conditions mainly because they specifically stimulate the brain into generating phosphenes, or they are placing strain on the optic nerve producing an emission of biophotons.
Less commonly, phosphenes can be tell-tale indicators of multiple sclerosis. Much like optic neuritis, what this disease does is it stresses the nerves in the brain, which in turn puts pressure on the optic nerve, which generates phosphenes. Now this is a rare case, so healthy people don't have much to worry about if they find themselves able to see phosphenes.
Other Kinds of Phosphenes edit
Pressure phosphenes are the most commonly seen amongst people, but there are those who find that they are able to see phosphenes without any of the normal stimuli as listed above. The second most common kind would be after someone has a bright light shone directly into their eyes, after walking into a dark room, or even just closing one's eyes. However, one does not need an absence of light in order to see phosphenes. There are some people who have been reported to have seen phosphenes even in broad daylight, and with their eyes open. One possible cause of this, if not natural, would be an open-eyed hallucination caused by some form of neurological mental illness, or certain types of hallucinogenic drugs.
External Links edit
"Phosphenes Induced by Sound" Simmons Lessell, Michael M. Cohen. First published November 1, 1979, DOI: https://doi.org/10.1212/WNL.29.11.1524. Accessed February 25, 2019.
"Why do we see colors with our eyes closed?" Hanneke Weitering. Published December 29, 2014, DOI: https://scienceline.org/2014/12/why-do-we-see-colors-with-our-eyes-closed/. Accessed February 20, 2019.
"Entopic Phenomena", Chapter 3 "The Evidence" Suzanne Carr. Published 1995, DOI: http://www.oubliette.org.uk/Three.html. Accessed February 15, 2019.
"Cellular mechanisms underlying the pharmacological induction of phosphenes" Br J Pharmacol. 2007 Feb; 150(4): 383–390. Published online 2007 Jan 8. doi: 10.1038/sj.bjp.0706998. Accessed February 26, 2019.