Researchers at Nagoya University in Japan have developed miniature brain models using stem cells to study interactions between the thalamus and cortex. Their work reveals the thalamus's key role in maturing cortical neural networks. The findings could advance research into neurological disorders like autism.
A team led by Professor Fumitaka Osakada and graduate student Masatoshi Nishimura at Nagoya University's Graduate School of Pharmaceutical Sciences has created assembloids—fused organoids derived from induced pluripotent stem (iPS) cells—that mimic connections between the human thalamus and cerebral cortex.
These lab-grown structures allow real-time observation of neural development. The researchers generated separate thalamic and cortical organoids, then combined them. Nerve fibers from the thalamus extended toward the cortex, and vice versa, forming synapses similar to those in the human brain.
Analysis showed that cortical tissue linked to the thalamus exhibited greater maturity in gene expression compared to isolated cortical organoids. Neural signals propagated from the thalamus to the cortex in wave-like patterns, inducing synchronized activity. This synchronization occurred specifically in pyramidal tract (PT) and corticothalamic (CT) neurons, which project back to the thalamus, but not in intratelencephalic (IT) neurons.
The study, published in the Proceedings of the National Academy of Sciences on November 19, 2025 (volume 122, issue 47), highlights the thalamus's role in organizing specialized cortical circuits essential for perception, thinking, and cognition. Such circuits often develop abnormally in conditions like autism spectrum disorder.
Osakada noted the implications: "We have made significant progress in the constructivist approach to understanding the human brain by reproducing it. We believe these findings will help accelerate the discovery of mechanisms underlying neurological and psychiatric disorders, as well as the development of new therapies."
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