Reduce. According to the doctor's online data, the synaptic density of the infant's cerebral cortex is much lower than that of adults at birth, and the number of synapses in the cerebral cortex will increase rapidly after birth due to the continuous development of the brain. The synaptic density in the cerebral cortex of children around 4 years old is the highest. Throughout childhood, the synaptic density remains much higher than that of adults. After human age reaches adolescence, the number of synapses will gradually decrease, approaching that of adults. With the gradual maturity of teenagers' physical development, the structure and function of the brain are also changing. In this process, some synapses will be pruned to optimize the connection and information transmission efficiency of neural network.