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A research team at Stanford University in the US announced that they successfully transplanted brain organoids (mini-brains) made from human iPS cells into newborn mice genetically engineered to barely form a cerebral cortex or hippocampus, getting the organoid to integrate with the mouse’s brain and actually function. The findings were published in the online edition of the British journal Nature on September 16. The same team ran a similar experiment with rats back in 2022, but since a rat’s brain grows faster than a human one, the results were of limited use — so this time they used mice that lack most of their brain, giving the transplanted human tissue room to grow. On 5ch, brief comments debating the ethics of the technology were followed by a string of replies bringing up related neuroscience topics.
Human brain organoid transplanted, found to function — in genetically engineered live mice, US university
A Stanford University research team announced in the online edition of the British journal Nature on the 16th that they turned human induced pluripotent stem (iPS) cells into a cluster of brain nerve cells and transplanted them into the cerebrum of newborn mice engineered to lack a cerebral cortex and a hippocampus (the memory center) — and the tissue grew together with the mouse’s brain and began functioning.
(Omitted below — see the source for the full article)
Source: jiji.com / Original article here
What people said
[Nazology] Part of the mechanism behind ADHD onset uncovered, offering a treatment lead for "people the meds don't work on" [Slime★]
2026/09/17
https://egg.5ch.io/test/read.cgi/scienceplus/1789652126/
Human mini-brain transplanted into a mouse skull: the current state of Stanford's cross-species cortex model
A study published in Nature transplanted human brain organoids into genetically engineered mice missing most of their cerebral cortex, reconstructing over 90% of the cortical region. Angiogenesis and the appearance of distinctive neuron types were confirmed, but the tissue's immaturity and the causal link to any behavioral improvement still call for careful verification.
September 17, 2026
https://xenospectrum.com/xenocortical-mice-human-brain-organoids-nature-study/
…made up of billions of neurons, and takes close to 20 years to fully mature.
Because the brain is shielded by the hard skull, there's been no way to observe at the cellular level how the postnatal brain develops.
So scientists have been building mini-brains called "brain organoids" from human stem cells and studying them in the lab instead.
But with older culturing methods, the neurons died off within a few months, so researchers could only observe the earliest, fetal-like stage.
This time, Harvard's Professor Paola Arlotta and her team focused on "firing" — the spontaneous electrical signals neurons put out.
Neurons are like muscles: stop using them and they atrophy.
The team used a special culture medium that sustains this spontaneous firing, and managed to keep mini-brains healthy for over 5 years.
The previous record was 694 days, so this is nearly three times as long. Some mini-brains in the lab have now hit the 7-year mark.
Published: 2026-09-08 08:00
https://karapaia.com/archives/626830.html
A sponge larva mid-metamorphosis. Image credit: Océane Blard, CC BY
It turns out that sponge larvae — which have neither brain nor nerves — can read changes in their surroundings and pull off a dramatic transformation of their own body.
A research team at the University of Queensland in Australia found that free-swimming sponge larvae start prepping for metamorphosis using "sunset" as their cue.
★When a larva senses darkness falling, it pre-loads the DNA it'll need for metamorphosis so it's ready to be read at a moment's notice. Thanks to this advance prep, once the larva finds a spot to settle, it can anchor itself in just 30 minutes and immediately start remodeling its body.
This research was published in the journal eLife (dated May 11, 2026).
★In the "healthy control" group and the "no hallucinations" group, this internal copy gets reinforced right before speaking, and it helps them properly predict their own voice.
★But in the "hallucinations" group, this mechanism was overactive even when they weren't trying to say anything in particular, kicking up disorganized "noise" in the brain.
In other words, these processes made it easy for them to mix up real sounds with their own thoughts.
★According to the research team, when these two negative factors combine, some schizophrenia patients become far more likely to perceive thoughts or noise generated inside their own brain as sounds coming from outside.
This study succeeded in revealing the disrupted brain signals behind auditory hallucinations in schizophrenia patients.
They also looked beyond external senses to interoception — the sense of what's happening inside the body.
Participants did two tasks: pressing a button whenever they felt their own heartbeat, and pressing a button in time with a recorded heartbeat sound.
At the same time, the team recorded ECG and EEG data and calculated the Heartbeat-Evoked Potential (HEP), a measure of how the brain reacts to each heartbeat.
Finally, by cross-referencing all these sensory-processing measures against how severe each patient's symptoms were, they analyzed how the neural processes behind distinguishing self from other were changing.
The research team explains this with a "prediction mismatch."
A healthy brain predicts the sensations its own actions are about to cause, and dampens its response when the prediction checks out.
But in patients with psychotic disorders, that prediction doesn't work properly, so self-generated stimuli can end up feeling like "unexpected outside stimuli."
That leads to misperceptions — your own voice sounding like someone else's, or feeling like someone else is controlling your body — which is thought to be behind symptoms like auditory hallucinations in schizophrenia and similar conditions.
This finding shows that the line separating "self" from "other" is shaped not just by the brain, but at as fundamental a level as the spinal cord.
That reframes hallucinations and delusions not as mere problems of the mind, but as glitches in sensory processing.
The team says they plan to explore whether training or neurofeedback that corrects this kind of sensory mismatch could help ease symptoms.
Background and key points of this discussion
Brain organoids are experimental mini-brain tissues grown from iPS or ES cells. Since they lack blood vessels, oxygen and nutrients struggle to reach them, and on their own they can’t replicate how they’d interact with other organs. The Stanford team first tried transplanting organoids into newborn rats back in 2022, but because a rat’s brain grows faster than a human one, there were limits to what could be observed. This time, the trick was using mice genetically engineered to barely develop a cerebral cortex or hippocampus, giving the transplanted human tissue room to grow without competition. On the thread, some posters raised ethical concerns about the technology, while others voiced hope that it could advance basic research into psychiatric disorders. That said, it’s easy to misread this as “a mouse born with human consciousness” — in reality, this is still basic research at the disease-model stage.
※This article is excerpted and summarized from the 5ch (Science News+) thread “Human brain organoid transplanted, found to function — in genetically engineered live mice, US university.”
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