Ummmmm... vision? In the eye
Alright so let’s just like… track a sight as it goes through your processes, that sound good?
I like… vividly remember using this exact image for a poetry journal in 9th grade. #SoPoetic, jk I suck at poetry and commend people with artistic skills.
SO Ray of light
Enters the pupil… everyone always talks about how your eye projects it upside down and I always thought that was some eye trick but no it’s like how if you shine a flashlight from the ground up, it ends up higher than a flashlight shining down from the ceiling… so if you shined (shown?) both at the same time, the lights would “flip” location. Am I the only person who always struggled with this concept? Yes? Ok this is awkward… ANYWAYS. So the light hits somewhere, after going through the lense, on the back of the eye. If it hits the optic disk, you don’t see it (#BlindSpot, we’ll get there), if it hits the fovea, that’s like, as clear as it gets (foveal vision makes up 70% of the input from your eye to your brain). If it hits vaguely in the center… hold on I’m gonna use my shitty photo editing skills (aka doodling on a powerpoint slide)
so THAT was probably a waste of time. I really could have just said “the periphery has more rods, while the in and near the fovea there are more cones” and gotten the same thing and not wasted a half hour on this illustration but what can I say… I enjoy being extra. I also blocked out the terms I have deemed “useless” on the grounds that… I don’t know what they are. CONE=COLOR… basically. That’s one way to remember them. They are less active in dim lighting, more active in bright lighting, and important for color vision. ROD=… the other one…, idk maybe peRipheRy?? They respond to faint light and are actually bleached by bright light… they’re abundant in the periphery.
So these are the cells of the retina basically anywhere that isn’t periphery or fovea. so follow the line, light shoots straight back to the receptors, and a bunch of receptors will send the information to one bipolar cell… and a bunch of bipolar cells sent it to one ganglion cell that zips it down the optic disk… so basically the information converges, which is good for efficiency, less good for precision. In the FOVEA you’re more likely to get a one to one ratio of these three cells. The amacrine cells kinda bippidy boppidy the fuck everywhere as you can see, they function as a sort of refinement. Like a cleanser that follows you around.
Horizontal cells function for lateral inhibition. Basically, it’s easier to tell where something is coming from when everything surrounding it is off. Like a light seems brighter when it’s surrounded by darkness than when it’s in light. So when light hits the receptor, the horizontal cell tells the other receptors to just fucking… shut up. Which clarifies the message, sharpens contrast in the image.
There are three kinds of ganglion cells
Parvocellular- small cell bodies, small receptive field, and occur in/near the fovea. Good for ID color and details
Magnocellular-pretty evenly spread throughout the eye, with a larger receptive field and cell body (likely what’s shown in the image above), important for movement and pattern detection.
Koniocellular- I hope I spelled that right. Small cell body found throughout the retina. In my notes I have written “Do many things” so there’s that.
Next post: into the brain.
Kalat, J. (2016). Biological Psychology. Australia South-Western. 12E