Controlling, Mapping, and Modeling Neural Circuits

## From stem cells to organoids **Pluripotent stem cells** can become almost any cell type. Guided with signaling molecules in 3D culture, they undergo **neural differentiation** and self-organize into a **cortical organoid**: a small tissue that reproduces some features of the developing human cortex, such as progenitor zones and early neuron types. pluripotent stem cell → neural differentiation → cortical organoid ## What organoids are — and are not Organoids reproduce **some** features of developing human neural tissue. They are **not** miniature adult human brains. They lack the size, layered maturity, blood supply, and connections of a real brain. ## Strengths - **Human genetic background:** cells can come from specific people, including patients. - **Developmental biology:** human-specific features of cortical development can be watched in the dish. - **Disease modeling:** genetic variants linked to neurodevelopmental disorders can be studied. - **Human cell-type development:** the emergence of human cortical cell types can be tracked. ## Limitations - **Incomplete maturation:** neurons stay relatively immature. - **Limited physiological environment:** no vasculature; nutrient supply limits growth. - **Limited sensory and body input:** no eyes, body, or normal inputs drive the tissue. - **Restricted circuit integration:** no long-range connections to other brain regions. - **No normal behavioral readout:** a dish cannot show how circuits affect behavior. ## A path forward **Transplantation** into a living animal host is one way to study how human-derived tissue matures and integrates **in vivo** — with blood supply, inputs, and a behaving host. That is the logic behind the xenocortication study in the next two lessons. ## The course framework GENES → CELL TYPES → CIRCUITS → NETWORK DYNAMICS → BEHAVIOR, studied by four complementary approaches: **map**, **record**, **perturb**, and **model**. Understanding a neural circuit requires several of these ways of observing and testing the same biological system. ## Further reading - [Deisseroth Lab (Stanford)](https://web.stanford.edu/group/dlab/) - Developmental xenocortication using human-derived organoids in mice. *Nature* (2026) — collaborative work by multiple Stanford groups and investigators.