Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: greenslime on 16/04/2010 21:57:17
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If it is pitch black or dark at night and you close your eyes why can you see little bright coloured dots like static. And if you look in the middle sometimes you can see like horizontal lightning bolts that come closer.
Why do we get this?
And when you are in a really quiet place where there is no sound whatsoever why is it that if you listen you can hear like a ringing noise in your ears?
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If it is pitch black or dark at night and you close your eyes why can you see little bright coloured dots like static. And if you look in the middle sometimes you can see like horizontal lightning bolts that come closer.
Why do we get this?
A phosphene is an entoptic phenomenon characterized by the experience of seeing light without light actually entering the eye ... Phosphenes can be directly induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex as well as by random firing of cells in the visual system.
http://en.wikipedia.org/wiki/Phosphene
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From what I recall in uni I think the theory is that the hair in your ears is moved my very small wind movements that you don’t feel or noticed. When the the wind enters your ears it goes through the narrow passageway and the sound it created in your earways. I think maybe this sound is always present but is suppressed as we do not notice it when we hear other things around us, but then when wesit in silence the sound becomes evident.
Gosh I think I am hearing it now, late at night while typing this on my computer :D
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Our neurons cant stop working. There activity can be suppressed, but once in a while they have to fire. This generates a constant "noise" in the perceptual systems that can't be detected when there are normal external stimuli present, but when there is no stimulus coming in you can sometimes detect this random noise in the system.
Although we are almost never in a stimulus free environment, and even if we are, our own body generates sounds (heartbeat, blood flowing in the bloodvessels near the ear, breathing, swallowing) so we are constantly hearing things. That's one reason why they use white noise instead of complete silence in sensory deprivation (http://en.wikipedia.org/wiki/Sensory_deprivation) experiments.
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And when you are in a really quiet place where there is no sound whatsoever why is it that if you listen you can hear like a ringing noise in your ears?
The term "tinnitus" usually refers to more severe cases. Heller and Bergman (1953) conducted a study of 100 tinnitus-free university students placed in an anechoic chamber and found that 93% reported hearing a buzzing, pulsing or whistling sound.
http://en.wikipedia.org/wiki/Tinnitus