What Two Parts of the Brain Are Still Underdeveloped When the Baby Is Born?

By Sarah Clark
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The human brain is a complex organ composed of many different parts that all have individual functions. A baby's brain is not fully developed when it is born. It takes years for the brain to be completely developed and capable of complex thoughts and actions. These activities are handled by the cerebral cortex. The motor strip is another underdeveloped part that more fully forms following birth. It handles basic motor movements.

The Motor Strip

The motor strip is located on both the left and right sides of the brain. This region is responsible for muscle movement and simple or gross motor skills. Gross motor skills include simple muscle movements throughout the body, like changing position or keeping balance, according to the University of Michigan Health System. Babies are not able to make many movements when they are first born. They are able to make more movements as the motor strip develops in the brain.

Development of the Motor Strip

Babies often develop muscle abilities in a certain order that coordinates with the development of the motor strip. First he develops the ability to turn his neck, making him able to turn and lift his head. Movements of the shoulder, upper arms and the hands follow sequentially. Then baby is able to sit up using his upper body. After that he can pull up his hips and pelvis, which ultimately leads to standing. The final gross motor skill to develop is muscle control in the legs that allows for standing, walking and running.

The Cerebral Cortex

Much of the upper portion of a baby's brain is underdeveloped at birth. A major part of this region is the cerebral cortex, which is responsible for things like voluntary movements, notes the publication Physical Therapy, from the Journal of the American Physical Therapy Association. The cerebral cortex is made up of four lobes. The frontal lobe is responsible for personality, memory, judgment and voluntary activities. The parietal lobe handles spatial orientation. The occipital lobe governs vision while the temporal lobe handles speech. The cerebral cortex and its hemisphere develop as a baby matures.

Development of the Cerebral Cortex

The cerebral cortex develops as a baby experiences new sensations and interacts with her environment. Connections between her nerves called synapses are created as responses to different stimuli. The mental processes using these synapses create memories of stimuli and experiences. These memories become more sophisticated as a baby ages and becomes more aware of the world around her. The cerebral cortex takes up to 10 years to fully develop, and continues to become more complex after that.

About the Author

Sarah Clark has been writing since 1997, with work appearing in Northern Arizona University's "Student Life Organization Newsletter." She holds a B.A. in anthropology with a minor in art history from Northern Arizona University.