How the Brain Grows and Why It Matters
The human brain doesn’t mature all at once—it develops in a very organized way. According to Dr. Robert Melillo, this process starts from the bottom and works its way up. Early in life, the brainstem and lower regions control basic survival functions (like eating, swallowing and breathing) and reflexes. These primitive reflexes, like grasping or rooting, are essential for newborns but should fade as higher brain areas develop. As the cortex matures, it begins to exert “top-down” control, calming these reflexes and allowing more voluntary, purposeful movements.
Another fascinating aspect of brain development is how each hemisphere takes turns leading the way. In the first two years (from birth until age 2), the right side of the brain grows more rapidly, supporting sensory processing, emotional regulation, and spatial awareness. The goal in the first 2 years of brain development is more ‘big picture’; having the child learn who they are and what they are doing here. Then, during the next two years, the left hemisphere takes the spotlight, driving language skills and analytical thinking. The goal in the 2nd two years is gathering and expanding detailed information on all the stuff that was processed in the first 2 years. This balanced progression is crucial for healthy cognitive and motor development.
Recent research adds even more insight. A study called Sensing Echoes by Torres shows that a simple newborn hearing test—the Auditory Brainstem Response (ABR)—can reveal subtle delays in brain signal timing. These delays may predict which children are at risk for autism, making ABR a powerful early screening tool. Similarly, Leisman and Melillo’s work on primitive reflexes suggests that if these reflexes linger beyond infancy, they could signal developmental challenges like ADHD or autism. Identifying these markers early gives parents and clinicians a chance to intervene sooner, supporting better outcomes for children.
We are pediatric specialist chiropractic office and looking for retained primitive reflexes (RPRs) is foundational in what we examine in children. We have found that children with more RPRs generally have more challenges, and between chiropractic adjustments and home-based neurological exercises, children can gain focus, improve calmness, have less outbursts, and generally become happier and healthier kiddos!
References:
https://academic.oup.com/pnasnexus/article/2/2/pgac315/7035935

