A hobby of mine is overthinking the neuropsychological implications of if Derek did get taken by the DMS and is somehow alive and conscious. It heavily depends on how exactly the infinite knowledge is acquired and stored on a neurological level but I’d hazard a guess to say its delivered via the optical nerves to the areas responsible for information storage (hippocampus, thalamus, amygdala). Perhaps it doesn’t use the optical nerves at all but I’d think it would because seeing Something is what delivered the knowledge. Generally damage to the optical nerves also leaves more of the eye damaged just by how the damage was acquired but I believe with this situation itd only be the ON, which makes understanding what itd be like a bit more difficult. Damage to the occipital nerves can have obvious consequences like vision loss and inability to filter out harmful types of light from the sun, to odd consequences like pareidolia (seeing faces in places there are none), skewed depth perception, inability to recognize faces or objects, not processing movement properly, or the eyes work perfectly fine but can’t transfer visual information to the brain but the patient still thinks they can see. Whether or not he still has the knowledge will impact how his information centers are affected. If he doesn’t have it, he’d have severe memory loss or complete amnesia. If the information leaving still left him with damage, he’d have significant issues forming, storing and locating new memories. If it didn’t, he’d have no problem with it. The visual center uses the information center to process what it’s seeing so it could make his understanding of what he can see, if he can see, a lot harder. Id also hazard a guess to say that hed have aura migraines, which is a weird thing the brain does (often a precursor to a seizure) where you see literal colorful auras around your sight just before or during a migraine. Depending on if The Horrors gave him brain damage all over, he could also have cluster headaches (the most painful type of headache) where all he can manage is to writhe around crying and throwing up until he’s heavily sedated. Dare I say he could also have a csf leak (the fluid surrounding his brain leaks out, generally from the nose, extremely dangerous if untreated). He would DEFINITELY develop major neurocognitive disorder from the insane amounts of brain damage. It could show up as tremors, stutters, difficulty processing words or putting his thoughts into words, non epileptic and epileptic seizures (probably focal, dissociative, absent types), hyper/hypotension, pre/syncope, nervous system dysfunction, muscle stiffness, loss of bodily coordination/balance, delusions, hallucinations, numbness, extreme sensitivity to stimuli, loss of impulse control.
As for psychological, I think hed be stuck in a fawn response and wouldn’t be able to put up much of a fight. He’d be scared and angry internally because it was one thing for a god to be so cruel to a human but it’s so much worse when it’s humans doing it to humans. He would be so afraid and weak that he wouldn’t even have the ability to be resistant. He’d be a bit like a wild bird caught in a birding net, letting the bird researchers do whatever they want out of fear but occasionally that impulsive instinct takes over making them freak out until theyve just exhausted themselves because they’re still in the net and very afraid. The bird doesn’t know what the researcher wants, it doesnt know if they’re gonna hurt them or help them or just look at them, it just sees something big and powerful. He’d learn to dissociate from it all, at least itd hurt less if he couldn’t process it at all. His emotions would be uncontrollable and unpredictable, brain unable to handle things like it should. He would want human connection so bad, in some fucked up way he just wanted some of the researchers to just be gentle and comforting with him but he wouldn’t trust any of them to give it.
If he were to escape and live with Avery or his mama, his psychological presentation would be much different. He wouldn’t have any reason to be afraid, he wouldn’t have a choice but to unmask everything he’d been hiding to survive. It wouldn’t be easy, for him or anyone around him. Hed have very little impulse control and severe mood swings. He’d have bouts of being rude, pushing away help, arrogant, cold, unsympathetic to the people around him. After he would crash and feel so guilty and hate himself for acting that way, he wouldn’t think he deserves forgiveness or care. He wouldn’t understand why they’re still around. He’d want to isolate so he didnt even have the chance to hurt them, but they wouldn’t let him. They know he doesn’t know how to handle this new brain of his and god knows they can’t judge him for it. Hed become really clingy, even physically latching onto them for comfort and because that rush of good chemicals his brain puts out makes everything a little better. Not only does he depend on physical touch to feel okay again but it’s one of very few ways he still has left to show how much he loves them.