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The retina technically is part of the brain. It does all sorts of signal compression and visual pre-processing before sending the signal (not pixels) to the vis

The retina technically is part of the brain. It does all sorts of signal compression and visual pre-processing before sending the signal (not pixels) to the visual cortex via the optical nerve. Somebody made some calculations on Quora - it is a factor of 6600 to 1 compression ratio or 40 exabytes from the rod/cone cells down to 6 petabytes along the optic nerve.

cbeach 3y ago
Interesting stats. Could you elaborate on the data you mentioned please? What does the 40 exabytes represent? Is that a single “frame” of an image captured by the eye? Or perhaps its data per second?
- stevenwoo 3y ago
  We know from studying lower life forms that they absolutely do not send some pixel accurate representation of an image(barring some incredible compression/encoding) From the seminal paper What the Frogs Eye Tells the Frogs Brain https://web.archive.org/web/20110928024235/http://jerome.lettvin.info/lettvin/Jerome/WhatTheFrogsEyeTellsTheFrogsBrain.pdf https://web.archive.org/web/20110928024235/http://jerome.let... to Guinea pig eyes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564115 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564115
- tibbydudeza 3y ago
  From Quora "Each eye has 137 million rods and cones. If we assume 8 bits per pixel and 60 frames per second for 2.5 billion seconds, then the total information from both eyes is 3.3 x 10^20 bits, or about 40 exabytes (40 million terabytes). More realistically, the retina does not transmit pixels directly to the brain. Instead, it detects low level features such as center-surround contrast and movement. Each optic nerve contains about 1 million fibers. We can't see events lasting less than about 0.1 seconds, so let us assume an information rate of 10 bits per second per nerve fiber. This is a total of 10^6 fibers x 2 optic nerves x 10 bits per second x 2.5 x 10^9 seconds = 5 x 10^16 bits, or 6 petabytes. This represents a lossy compression ratio of 6600 to 1. The brain's visual cortex compresses this data further by detecting a hierarchy of increasingly complex shapes such as edges, lines, angles, characters, shapes, and objects such as faces. In a 1986 study in which people were asked to learn and recall thousands of pictures, Tom Landauer estimated that human long term memory is on the order of 10^9 bits, or 1 bit per second. If we assume that 40% of our long term memory is visual (in proportion to the size of the visual cortex), then it suggests that the retina and brain compress visual data at a rate of (3.3 x 10^20 / 4 x 10^8) = 825 billion to 1." https://qr.ae/pKofqQ https://qr.ae/pKofqQ
  - cbeach 3y ago
    Ah so it's the input data over the course of a human lifetime. Thanks!
shiroiuma 3y ago
It's true that the retina and optic nerve do a lot of processing, but that doesn't make them part of the brain. The spinal cord does its own processing too (including reflexes), but it's not part of the brain either. According to your logic, my USB-connected webcam is part of my computer's CPU (or at least motherboard). It isn't, even though it does a lot of processing on its own and probably has a CPU of its own inside.
- tibbydudeza 3y ago
  Reflexes are simply a hardwired circuits because waiting for high order thought processing up to the brain in response to certain stimuli (pain) will end up you being rather dead or badly injured. The retina has the same layered architecture of a scaffold of neurons and support cells as your cerebral cortex.

cbeach 3y ago

Interesting stats. Could you elaborate on the data you mentioned please? What does the 40 exabytes represent? Is that a single “frame” of an image captured by the eye? Or perhaps its data per second?

stevenwoo 3y ago
We know from studying lower life forms that they absolutely do not send some pixel accurate representation of an image(barring some incredible compression/encoding) From the seminal paper What the Frogs Eye Tells the Frogs Brain https://web.archive.org/web/20110928024235/http://jerome.lettvin.info/lettvin/Jerome/WhatTheFrogsEyeTellsTheFrogsBrain.pdf https://web.archive.org/web/20110928024235/http://jerome.let... to Guinea pig eyes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564115 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564115
tibbydudeza 3y ago
From Quora "Each eye has 137 million rods and cones. If we assume 8 bits per pixel and 60 frames per second for 2.5 billion seconds, then the total information from both eyes is 3.3 x 10^20 bits, or about 40 exabytes (40 million terabytes). More realistically, the retina does not transmit pixels directly to the brain. Instead, it detects low level features such as center-surround contrast and movement. Each optic nerve contains about 1 million fibers. We can't see events lasting less than about 0.1 seconds, so let us assume an information rate of 10 bits per second per nerve fiber. This is a total of 10^6 fibers x 2 optic nerves x 10 bits per second x 2.5 x 10^9 seconds = 5 x 10^16 bits, or 6 petabytes. This represents a lossy compression ratio of 6600 to 1. The brain's visual cortex compresses this data further by detecting a hierarchy of increasingly complex shapes such as edges, lines, angles, characters, shapes, and objects such as faces. In a 1986 study in which people were asked to learn and recall thousands of pictures, Tom Landauer estimated that human long term memory is on the order of 10^9 bits, or 1 bit per second. If we assume that 40% of our long term memory is visual (in proportion to the size of the visual cortex), then it suggests that the retina and brain compress visual data at a rate of (3.3 x 10^20 / 4 x 10^8) = 825 billion to 1." https://qr.ae/pKofqQ https://qr.ae/pKofqQ
- cbeach 3y ago
  Ah so it's the input data over the course of a human lifetime. Thanks!

shiroiuma 3y ago

It's true that the retina and optic nerve do a lot of processing, but that doesn't make them part of the brain. The spinal cord does its own processing too (including reflexes), but it's not part of the brain either. According to your logic, my USB-connected webcam is part of my computer's CPU (or at least motherboard). It isn't, even though it does a lot of processing on its own and probably has a CPU of its own inside.

tibbydudeza 3y ago
Reflexes are simply a hardwired circuits because waiting for high order thought processing up to the brain in response to certain stimuli (pain) will end up you being rather dead or badly injured. The retina has the same layered architecture of a scaffold of neurons and support cells as your cerebral cortex.