• batmaniam@lemmy.worldEnglish
    47 seconds

    Another fun eye/brain fact: There are two “outputs” for each eye. One goes to your occipital lobe, in the back, and really processes the image (“That’s a cup, it <holds liquid> <is firm with a medium weight>…” etc) and one goes to your brain stem, which processes movement.

    It’s possible to have the connection to the occipital lob severed, but not to the brain stem. It’s a condition called blindsight. The result is that if you showed someone a cup, they wouldn’t be “see” it; they wouldn’t know what it is and wouldn’t register you were showing them anything at all… but if you tossed it to them they could catch it.

  • village604@adultswim.fanEnglish
    1 day

    Fun semi-related fact:

    Have you ever walked outside on a bright day and it’s so bright it hurts? Turns out there’s a max pain limit from brightness per eye, and your brain adds them together.

    By closing one eye, you cut the total possible pain in half.

    • IPeaceInYourFace@lemmy.worldEnglish
      6 hours

      Anybody else close one eye when it’s too loud and they need to think?

      Now it makes sense.

      Less GPU usage by eyeballs, more capacity for prediction algorithms.

    • NABDad@lemmy.worldEnglish
      21 hours

      Absolutely unfun semi-related fact:

      Sometimes when one eye is injured, the injured eye has to be removed or your body will decide the uninjured eye is bad and your immune system will destroy it.

      Sympathetic Ophthalmia

      If the injured eye has no chance of recovery, they scoop it out.

        • NABDad@lemmy.worldEnglish
          16 hours

          Yeah, the immune system can be moronic. Intelligent design my ass.

          However, there’s something extra special about getting poked in one eye and having your own immune system decide that an eye for an eye means your good eye has to die.

          • cynar@lemmy.world
            English
            3 hours

            I think the immune system can’t see the eye, so it’s never trained to avoid it. If the eye is damaged, the immune system can become aware of it and start reacting. Once it starts, pulling it back is not easy.

            The immune response system is simultaneously amazing and insane.

            It basically deliberately scrambles part of the DNA in the immune cells that create antibodies. The rest of the body then sheds cells into the blood to move to the lymph nodes. Any immune cells that react then self destruct.

            It’s the equivalent of firing a paint blunderbuss at a wall, and creating a silhouette by standing in the way!

            • NABDad@lemmy.worldEnglish
              2 hours

              My immune system pisses me off constantly.

              It let COVID through three times despite me rigorously keeping up to date with the vaccines as much as possible, and at the same time it has destroyed my thyroid gland and it has declared cherries and peaches as terrorist infiltrators.

              I feel like if my immune system is so bored it needs to attack harmless things, I should never have to deal with any actually harmful thing.

              It’s like a cop that beats up an unarmed teenager, but hides when someone is shooting up a school.

              • cynar@lemmy.world
                English
                2 hours

                I definitely think there are grounds to the cleanliness hypothesis. Basically the immune system expects a certain amount of activity. If it’s underperforming, the body systems assume it’s a problem with the immune system, not a lack of bugs, because we are too clean. It then racks up activity levels, causing problematic autoimmune or allergy reactions.

    • Jax@sh.itjust.worksEnglish
      20 hours

      Huh, I’ve always closed one eye when it’s super bright because it’s simply more comfortable. Cool to have the behavior defined this way.

      • AItoothbrush@lemmy.zipEnglish
        10 hours

        I never knew why the hell that worked, it seemed so bizarre and knowing it this way really is cool

    • cevn@lemmy.worldEnglish
      1 day

      This explains why I have to close one eye to go outside in the sun lol

    • Kairos@lemmy.todayEnglish
      1 day

      Is this that odd? We experience less pain if one of two arms has a knife in it instead of both.

      • SpacetimeMachine@lemmy.worldEnglish
        24 hours

        It is a bit odd. Your eyes feel pain to tell you whatever you are seeing might damage them if you look too long. But if you close one eye the pain can disappear entirely, even though that single eyes experience is the exact same.

        • Kairos@lemmy.todayEnglish
          24 hours

          So it is averaged over both eyes. Do yoh experience any pain in one eye? Or is it always averaged over both?

    • NOT_RICK@lemmy.worldEnglish
      1 day

      That is fun, I’ve wondered why that is. I also think sometimes when it’s super bright out it makes me sneeze.

  • whyNotSquirrel@sh.itjust.worksEnglish
    1 day

    I met a person long ago that had one hemisphere “dead” after several strokes. So their vision was cut in half in a way I couldn’t really understand before I found out about this.

    So they could just see one side (left maybe) but with both eyes, like if you took a screenshot of a FPS view and completely cut off one half of the image

    • Whats_your_reasoning@lemmy.worldEnglish
      20 hours

      I literally just finished having a migraine aura (it’s only the second time I’ve had one, though no headache the first time and no headache yet now.) I was reading a bit about it and how it’s a caused by a slow wave going across one’s brain. It started in the middle of my vision on the drive home, and after I arrived it continued sweeping off to my left field of vision until it dissipated off into the periphery a few minutes ago.

      It’s interesting to look at this image and imagine the wave going across the back of my right brain hemisphere. It’s also interesting how even the visual looked like the cone-shaped wave that follows a sonic boom, slowly spreading out.

      And now, with such dire imagery and the potential for upcoming pain, I’m going to lie down and hope nothing else happens.

      • LetThereBeNick@lemmy.zipEnglish
        20 minutes

        It is really cool to perceive some of the structure of your visual cortex in cases like this. Another example is watching the patterns when your eyes are closed for a while in a dark room. Those spreading waves you can sometimes see resemble the activity recorded from cortex at rest.

      • Rachelhazideas@lemmy.worldEnglish
        10 hours

        Wish you a speedy post-drome. I had migraines for a year in the past, and the thought of going through that again fills me with dread.

  • Iconoclast@feddit.ukEnglish
    1 day

    The so-called “split brain” studies on people who have had the bridge between the two hemispheres - the corpus callosum - cut to treat grand mal seizures are fascinating. They use this method to communicate with each hemisphere separately without the other knowing.

    You can, for example, give one an instruction to do something. After it has done it, you ask the other (verbal) hemisphere why they just did that, and they immediately make up a plausible-sounding explanation despite the scientists knowing it’s not the actual reason.

    You also get different answers for questions about dream jobs and such.

    This all sparks the question: Are there two “people” in our brain the whole time or is the other created the moment the connection is cut? And which one is what I call “I”?

    • Swedneck@discuss.tchncs.deEnglish
      6 hours

      what i want to know is whether making up an explanation is universal, or if other people would just go “no clue”.
      Because if EVERYONE with a severed corpus callosum just makes up explanations that is very fucking uncomfortable to think about, and i’ll treasure having mine intact

      • Iconoclast@feddit.ukEnglish
        5 hours

        I’m no neuroscientist but I don’t think this has anything to do with the two hemispheres being separated - it’s just how the human mind works. When something happens we come up with an explanation for it that’s sometimes factual and sometimes completely made up. These people don’t know that they’re making it up - they genuinely believe the reason they’re giving. We’re not comfortable with uncertainty, especially when it comes to our own behavior.

        I’m personally one of the people who doesn’t believe in free will so these findings make perfect sense to me and are in no way in conflict with my worldview, but I get how hearing about this might make someone else uncomfortable.

    • partofthevoice@lemmy.zipEnglish
      17 hours

      2 people, that’s it? What if you are a voice machine, just voices all the way down… but you only recognize the loudest as yourself?

    • enchantedgoldapple@sopuli.xyzEnglish
      19 hours

      I’ve seen this topic covered briefly in one of CGP Grey’s videos. The video also gives a POV of a person with this syndrome. The POV was surprisingly interesting to watch and I was wondering if there are other similar recorded experiments.

    • nogooduser@lemmy.worldEnglish
      1 day

      You can, for example, give one an instruction to do something. After it has done it, you ask the other (verbal) hemisphere why they just did that, and they immediately make up a plausible-sounding explanation despite the scientists knowing it’s not the actual reason.

      Sounds like AI got something right then.

      • Iconoclast@feddit.ukEnglish
        9 hours

        There’s an uncomfortable amount of similarities between how the human brain and LLMs work.

        Next word correlating with the words said before, confidently spreading false information, telling people what they want to hear… These are by no means unique to LLMs.

    • Airfried@piefed.socialEnglish
      20 hours

      You can, for example, give one an instruction to do something.

      How would you do that? Since both eyes are connected to both hemispheres isn’t it kind of hard to do that? Or are both ears separated and you can give commands through that without the other hemisphere knowing? I’ve heard about these studies too but I’m not sure about how the setup works because I’ve heard they used text on a screen for that but OP said the eyes do snitch to the other half after all. I find it a little confusing.

      • Iconoclast@feddit.ukEnglish
        9 hours

        By building a setup that allows the researchers to flash text on the right/left visual field. On a normal brain this information does indeed travel between the hemispheres but on a split brain it doesn’t.

  • Arcane2077@sh.itjust.worksEnglish
    1 day

    One eye per hemisphere? Are you that one Hollywood exec who insists humans only use 1% of their brain?