hey, i dont know much about turtology/tortology, nor do i know much about the eye other than i need glasses because my eyes are a weird shape. could somebody ELI5 please. for us plebs.
You can largely think of mammalian eyeballs as camera sensors, which see the world and pass lightly pre-processed pixel data through cables (your optic nerves) into the back part of your brain where your visual cortex "starts". That pixel-level data flows through a kind of pipeline of filters which detect increasingly complex features the further forward they are in the brain.
The first few layers are detecting fairly understandable things - like little lines bits, and corners that turn left, or turn right, etc. The downstream layers take those detections as inputs to detect more complex features, e.g. helping to detect larger closed shapes and determine which pixels are inside vs. outside those shapes. This data then feeds into higher level object detection, etc etc.
What's really cool is that the first few layers of this are more or less laid out like an image in RAM. A star pattern of shapes in the real world would cause a star pattern of neurons in your head to start firing. This sensible layout has really helped neuroscientists grasp what the brain is doing, and has IMO been one of the big reasons we've been able to take such inspiration from neuroscience into machine vision.
Apparently though, the turtle brain doesn't work like this at all. As far as I can tell, the turtle visual processing system is just a big weird soup of neurons with no familiar structure to it. It works somehow, and I'm excited to follow the progress of decoding what it's actually doing.
By the way, if any of this interests you I recommend grabbing a copy of David Marr's book "Vision". It's probably pretty out-dated at this point, but it's wonderfully written and I think gets the basic points across very well: https://mitpress.mit.edu/books/vision