Brain Development

Foetal Brain Development

The brain begins to develop very soon after conception as brain cells begin forming at the tip of the embryo. By 3 1/2 weeks, this neural tube begins to expand and mature to form the spinal cord and brain. Within the neural tube, brain cells or neurones begin to develop and send messages to each other.

At first, brain cells multiply quickly at a rate of 250,000 per minute. After the 20th week, a slowdown occurs as the brain organises itself into more than 40 systems.

By the 6th month, nearly all the neurones needed for life are present.

During the last 3 months, the connections between neurones grow longer, thicker, and more plentiful. The strongest will grow into distinct parts of the brain.

The systems that have been formed eventually direct vision, language, movement, hearing, and other functions. The surviving neurones continue to send out long transmission lines, literally trillions of them, to build up the foetus's nervous system.

We once believed that a newborn's brain was completely "wired" at birth. Now we know that many of the important brain connections that help to determine who we are, how we think, and how we handle our emotions develop after birth.

Postnatal Brain Development

Although it has already undergone an amazing amount of development, the brain of a newborn baby is still very much a work-in-progress. It is small - 25% of its adult size & weight - and strikingly uneven in its maturity. By birth, only the lower portions of the nervous system (the spinal cord and brain stem) are very well developed, whereas the higher regions (the limbic system and cerebral cortex) are still rather primitive.
The lower brain is therefore largely in control of a newborn's behaviour (cf. reflexes ), while the cerebral cortex is still quite immature. As the highest, most recently evolved part of the brain, the cerebral cortex is responsible for all of our conscious thoughts, feelings, memories, and voluntary actions.

Although all of the neurones in the cortex are produced before birth, they are poorly connected. In contrast to the brain stem and spinal cord, the cerebral cortex produces most of its synaptic connections (connections between neurones) after birth, in a massive burst of synapse formation known as the exuberant period . At its peak, the cerebral cortex creates an astonishing two million new synapses every second. With these new connections come a baby's many mental milestones, such as colour vision, a pincer grasp, or a strong attachment to his parents.

By 2 years of age, a toddler's cerebral cortex contains well over a 100 trillion synapses. Beginning in the middle elementary school years and continuing until the end of adolescence, the number of synapses then gradually declines down to adult levels.

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