**6. Conclusions**

NIRS can greatly aid in extending our existing experimental paradigms. With NIRS, we can measure haemodynamic changes in the cerebral cortex of children, and accumulate more information on brain activity from infancy to adolescence. Such information is of great importance in studying brain function from a developmental perspective. However, surprisingly, the available research, even on topics like the typical trajectory of functional brain development, is less.

Furthermore, research on atypical brain function in ASDs or ADHD is needed to clarify the differences between typical and atypical functional brain development. The understanding of brain function in children with psychiatric disorders is key to developing effective intervention methods. For early intervention, we need to elucidate the process of cognitive neurodevelopment in the early stages of development. Thus, NIRS is a valuable modality for monitoring and investigating brain activity in children with psychiatric disorders.
