By Nicole Gregory Of all the caregiving tasks you’ll perform for your newborn, the most daunting may be helping her develop optimally. And development of her brain seems particularly crucial. While it may feel like a big responsibility, experts say that all you need to do is what parents have done for thousands of years: Hold her, look at her, talk and sing to her, and respond to her needs. Interaction with parents does more for a baby’s brain in the first year of life than anything else. How baby’s brain grows A baby is born with 100 billion brain cells, and this number increases exponentially as her brain begins to develop. “Infancy is a period of rapid growth and change,” says Anna Penna, M.D., Ph.D., assistant professor of Pediatrics at Stanford University School of Medicine. “Neurons in the cortex [front and top of the brain] are all born by the time a baby is delivered at term,” she says, “but neurons in the cerebellum—a region at the back of the brain that is involved in motor control, cognition and error correction— are still being born for the fi rst few years of childhood.” Different parts of the brain develop at different rates. Vision, for instance, is immature at birth, designed only to see a parent’s face up close. But at 3 months, a baby can track a moving object. By age 1, her vision is like an adult’s. Hearing, however, is perfect at birth. By 3 months a baby will know your voice, and look for you when she hears it. Sights, sounds, touches and smells flood a baby’s brain and it becomes a dynamic activity center. NEXT: What does a baby’s brain need?