The construction of the nervous system is one of the most complex processes in embryology. Development of the nervous system, or neural development (neurodevelopment), refers to the processes that generate, shape, and reshape the nervous system of animals, from the earliest stages of embryonic development to adulthood. In vertebrates, it begins with the formation of the neural tube from the ectoderm via neurulation. This tube then differentiates into the brain and spinal cord through regionalization and patterning by morphogen gradients. Subsequent stages include neurogenesis (the birth of neurons) neuronal migration, axon guidance, synaptogenesis, and extensive activity-dependent refinement to produce functional neural circuits. This field of neural development draws on both neuroscience and developmental biology to describe and provide insight into the cellular and molecular mechanisms by which complex nervous systems develop, from nematodes and fruit flies to mammals.
Recent advances in genomics and imaging technologies, such as single-cell sequencing and live-cell microscopy, have refined our understanding of neural development at molecular and cellular levels. Techniques such as single-cell RNA sequencing allow researchers to profile gene expression in individual neural progenitors and neurons, revealing previously unknown cellular diversity during development. Defects in neural development can lead to malformations such as holoprosencephaly, and a wide variety of neurological disorders including limb paresis and paralysis, balance and vision disorders, and seizures, and in humans other disorders such as Rett syndrome, Down syndrome and intellectual disability.
