It’s part of an effort to better study human brain development and diseases affecting this most complex of organs, which makes us who we are but has long been shrouded in mystery.“Many disorders such as autism and schizophrenia are likely uniquely human” but “the human brain certainly has not been very accessible,” said said Dr. Sergiu Pasca, senior author of a study describing the work, published Wednesday in the journal Nature.Pasca, a psychiatry professor at the Stanford School of Medicine, said this is the first time these organoids have been placed into early rat brains, creating “the most advanced human brain circuitry ever built from human skin cells and a demonstration that implanted human neurons can influence an animal’s behavior.”To examine a practical use of this approach, scientists transplanted organoids into both sides of a rat’s brain: one generated from a healthy person’s cells and another from the cells of a person with Timothy syndrome, a rare genetic condition associated with heart problems and autism spectrum disorder.For example, researchers at ETH Zurich in Switzerland published a study in Nature earlier this month describing how they are growing brain-like tissue from stem cells in the lab and then mapping the cell types in various brain regions and genes regulating their development.Such research, he said, should help scientists make strides that have been extremely difficult until now because it’s so hard to get at the human brain – which is “the reason why we’re so much more behind in psychiatry compared to any other branch of medicine in terms of therapeutics.”___The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education."