During weeks 8 to 10, the cerebrum begins its development in earnest. Neurons proliferate and begin their migration throughout the brain. The anterior commissure, which is the first interhemispheric connection (a small one), also develops. Reflexes appear for the first time during this period
Reference:
1- Larsen's Human Embryology textbook ( Sixth Edition ).
2- the anatomy of human embryo electron microscope textbook ( 1st Edition ).
3-langman medical embryology textbook ( Fourteenth Edition ) .