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> It was only after they traced chemicals in the brain that they were able to verify that, indeed, the hippocampus was that squished, displaced object pushed to
by anonytrary 7y ago
> It was only after they traced chemicals in the brain that they were able to verify that, indeed, the hippocampus was that squished, displaced object pushed toward the back of the brain.
Main takeaway (misleading title) is that this rat had a brain, but a region of fluid developed and pushed the brain towards the edges of the cranial cavity. The rat was still able to do most of the other basic tasks as the other rats, but may have suffered from anxiety.
And that's the extent of this article. I don't think we know how higher order functions were affected. I would guess that these (like what humans have) are not necessary to sustain life. A species can exist indefinitely as long as they can feed and reproduce faster than they die. These things are easy to do without higher order functions if food and reproductive mates are readily available.
I wouldn't be surprised if a lab rat without 99% of their brain didn't change much or could still complete basic tasks. I would be surprised if a human without 99% of their brain could function normally in society today, which requires relatively heavy higher order brain function.
- saurik 7y agoHuh. I had a memory of reading about a human who had the same issue you quoted (I honestly have not clicked through to the article about the rat) and found an article about it with images I am finding extremely familiar. > A man with an unusually tiny brain manages to live an entirely normal life despite his condition, which was caused by a fluid build-up in his skull. > Scans of the 44-year-old man’s brain showed that a huge fluid-filled chamber called a ventricle took up most of the room in his skull, leaving little more than a thin sheet of actual brain tissue (see image of the patient’s brain, above left). https://www.newscientist.com/article/dn12301-man-with-tiny-brain-shocks-doctors/ https://www.newscientist.com/article/dn12301-man-with-tiny-b...
- anonytrary 7y agoWell, as promised, color me surprised. Either the brain is extremely resilient to compression, or being a human is easier than I thought...
- deleted 7y ago[deleted]
- jarfil 7y agoThe important part is the cortex, so in this case he might have lost some white matter connectivity but kept most of the gray matter structures. IQ of 75, though.
- FeepingCreature 7y agoBut see also /u/gwern's excellent writeup on these dramatic images: https://www.gwern.net/Hydrocephalus https://www.gwern.net/Hydrocephalus
- quickthrower2 7y agoInteresting piece thanks. The tl;dr is we probably need all the neurons inside our brains and evolution didn’t miss a trick to make us run on mini brains.
- foobar_ 7y agoGoddamn, that is the stuff of nightmares. I think it makes sense to think in terms of smaller neural networks that can do more. It makes sense. I don't know how Game AI Enemies are scripted but they seem to use very minimal code. This should also imply that the spinal cord is more important, as the brain is just 1/10ths ? of the nervous system.
- RankingMember 7y agoI don't understand why you and Gwern consider it to be the stuff of nightmares. It's a medical abnormality, but I don't understand the fear response.
- goto11 7y agoMaybe true depending on the definition of "entirely normal life", but an IQ of 75 indicate severe mental damage.
- tokai 7y agoNo, not severe mental damage. Most schemes would put him in the borderline category. That is he's on the cusp of being mentally impaired.
- mattkrause 7y agoIt's actually amazing how much rats (and people) can do despite massive brain damage. A rat with no cortex can do almost everything (other than trimming its nails!). The classic summary of these studies is by Whishaw (1990), and there's a copy of it (and similar stuff on humans) in this thread: https://twitter.com/markdhumphries/status/1071052762765541376?lang=en https://twitter.com/markdhumphries/status/107105276276554137... I once met a patient who was missing literally half of their brain due to an epilepsy resection + meningitis. We had a perfectly normal conversation and, had I not seen the MRI, I never would have guessed.
- lr4444lr 7y agoWhere was he clinically observed to be deficient, if at all?
- mattkrause 7y agoThe patient's vision was affected, though not as much as one would think. Visual areas in the left hemisphere represent the righthand size of visual space, while those in the right hemisphere represent the the left part of the world. With one hemisphere totally removed, you'd think the patient would be half blind. However, Dan Guitton's lab showed that D.R. still has some residual "blindsight" and that stimuli flashed in the blind hemifield affect eye movements. I'm not sure what else, though the patient had a rather normal life: held down a job, was involved in some civic organizations, stuff like that.