differentiating them into neurons often leads to small sample sizes for most reported studies. Currently, scaling up the experiments to include more subjects remains a major obstacle. However, new techniques are being developed to reduce the time and costs required to generate patient-specific neurons.101 Sixth, the pathogenesis of many neuropsychiatric diseases most likely lies at the level of neuronal circuits, making them difficult to study using iPSC technology. Co-culture systems102 and 3-dimensional organoids103, 104, 105 provide systems potentially capable of recapitulating circuit level interactions, to address this challenge. Importantly, iPSC-derived neurons have also been grafted into animal models to observe their circuit level interactions in vivo.74, 106, 107, 108
