How do we see?
Yesterday, I gave you a simplistic view of how we hear. It really isn't that simple but who has time to take a graduate course in auditory physiology? Today I would like to focus in on how we see which is actually easier to understand. Hearing is like an analog to digital back to analog converter. Vision is more like the collection plate of a camera.
The primary sensory organ at the back of the eye is called the retina. Our eyeball and lens are designed to focus and concentrate light but the image projected on the back of the retina is more or less a faithful spatial representation of the world. At the center of the retina is the fovea which has the largest concentration of cones, the receptors that detect color. Around the periphery are the rods which can't detect color but are much more sensitive to light which helps us see at night. We have about 125 million photo-receptors total. Even the highest resolution TV on the market today, an 8K UHD TV, only has 33 million elements. Nobody has invented a TV which has the same acuity as our retinas.
Interestingly (and not on me!) if you could tease apart the optic nerve and somehow re-sort it into the proper coordinates, the neural impulses would still faithfully represent the spatial image on the eye. Yesterday I explained that the temporal elements of the sounds we hear are already destroyed by the time they hit the auditory nerve. They have to be reconstructed as you get higher in the brain. Not so with visual images.
From the retina, the signals are passed up via the optic nerve to the lateral geniculate nucleus and from there it is just a hop, skip and jump to the visual cortex, complete with crossing over so as to facilitate stereoscopic vision. So the visual system is very easy to understand. Except for the technological hurdles (like no camera exists at high enough resolution and no one would know how to map external input to the visual cortex), I would think that a true visual prosthesis will be available some day for the blind long before an adequate hearing replacement is found.
By now, two articles in, you are probably asking yourself why the hell does a science fiction writer want to bog us down with anatomy and physiology? Reason: I want to explain how my robots, livetars and computers see and hear. It is totally, totally unlike humans. More on that tomorrow.
The primary sensory organ at the back of the eye is called the retina. Our eyeball and lens are designed to focus and concentrate light but the image projected on the back of the retina is more or less a faithful spatial representation of the world. At the center of the retina is the fovea which has the largest concentration of cones, the receptors that detect color. Around the periphery are the rods which can't detect color but are much more sensitive to light which helps us see at night. We have about 125 million photo-receptors total. Even the highest resolution TV on the market today, an 8K UHD TV, only has 33 million elements. Nobody has invented a TV which has the same acuity as our retinas.
Interestingly (and not on me!) if you could tease apart the optic nerve and somehow re-sort it into the proper coordinates, the neural impulses would still faithfully represent the spatial image on the eye. Yesterday I explained that the temporal elements of the sounds we hear are already destroyed by the time they hit the auditory nerve. They have to be reconstructed as you get higher in the brain. Not so with visual images.
From the retina, the signals are passed up via the optic nerve to the lateral geniculate nucleus and from there it is just a hop, skip and jump to the visual cortex, complete with crossing over so as to facilitate stereoscopic vision. So the visual system is very easy to understand. Except for the technological hurdles (like no camera exists at high enough resolution and no one would know how to map external input to the visual cortex), I would think that a true visual prosthesis will be available some day for the blind long before an adequate hearing replacement is found.
By now, two articles in, you are probably asking yourself why the hell does a science fiction writer want to bog us down with anatomy and physiology? Reason: I want to explain how my robots, livetars and computers see and hear. It is totally, totally unlike humans. More on that tomorrow.
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Tales of the Vuduri
Tidbits and insights into the 35th century world of the Vuduri.
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