The present invention (1) performs an operation of decreasing the number of copies of a FoxG1 gene from two copies to one copy in both differentiated excitatory neurons and differentiated inhibitory neurons present in a brain, or (2) performs, seven or more days after birth, an operation of increasing expression levels of a FoxG1 gene in both differentiated excitatory neurons and differentiated inhibitory neurons present in a brain to 1.2 to 2.0 times that of a wild type animal.
