Neurons also mature with the help of non-neuron cells called glia. Glial cells not only provide chemical signals like breadcrumbs, but at times, can also provide physical architecture to assist with migration. For example, glial cells known as Bergmann glia act as a branch on which two cerebellar neurons, Purkinje and granule cells, will climb through the brain to their ultimate destination of the cerebellum.
What changes after birth?
The developing brain engages in an intricate dance with its outside environment and is a sponge for information. During early development, 700 to 1,000 new neural connections are formed every second.
These early connections are the fundamental groundwork and precursors for more sophisticated connections later on. Although it is very important for new neurons to form long-lasting connections, it is equally important to trim away unnecessary connections. This process, known as synaptic pruning, allows only very important and useful connections to remain, while unused links between neurons are removed. Synaptic pruning occurs a great deal in early childhood, but also occurs during adolescence and adulthood.
Not only are connections between neurons regulated, but the actual number of neurons is also regulated by something known as programmed cell death, or apoptosis. Embryonic development gives rise to an overproduction of neurons. Although still not completely understood, apoptosis during this time occurs in response to both environmental and genetic factors.
New neurons make up only a small percentage of the total number of neurons in the adult brain. New connections between neurons, on the other hand, are constantly being formed, removed, and replaced. New connections are made when you learn skills and make memories. Connections can be lost when you fail to use or strengthen them. New research suggests that certain parts of your brain, especially areas involved in planning and working memory—also known as short-term memory—continue to develop and mature their connections well into your twenties.