Table 1.

hiPSC-based models to investigate neural circuit formation.

Model type	Neuronal cell types	Description	Application	References
Whole Brain Organoid	Glutamatergic (photoreceptors, retinal ganglion cells, bipolar cells, callosal neurons, corticofugal neurons); GABAergic and amacrine interneurons	Established proof of principle for neuronal connectivity and functional networks within brain organoids	Analysis of neuronal network dynamics	(30)
Fused Brain Organoid (Assembloids)	(i) Glutamatergic pyramidal neurons, GABAergic interneurons (ii) Glutamatergic pallium neurons, GABAergic subpallium interneurons	(i) Fused cerebral organoid model using GLU pyramidal neurons and GABA interneurons (ii) Fused spheroid model used to investigate Timothy syndrome	Local cortical circuitry (established through migratory GABAergic neurons) Local cortical circuitry (established through migratory GABAergic neurons)	(47) (48)
Microfluidic Chip	(i) Glutamatergic, GABAergic, dopaminergic (ii) Glutamatergic CA3 pyramidal and dentate gyrus neurons (iii) Medium spiny glutamatergic	(i) Fabrication of microfluidic device for analyzing neural circuitry (ii) Use of CA3 pyramidal and dentate gyrus neurons to explore perturbed hippocampal connectivity in schizophrenia (iii) Use of mouse neurons to model circuit disruptions in Huntington's disease	Three-way midbrain circuitry Mossy fiber hippocampal circuitry (DG-CA3 circuitry) Cortical-striatal circuitry	(34) (35) (36)*
Brain Organoid Transplant	See whole brain organoid	Integration, vascularization, and functional connectivity of human brain organoids into mouse brains	Cortico-cortico circuitry (In vivo model)	(49)

^*Used mouse primary neurons.