Early Brain Development
How the Brain Builds Itself
You started life as a single cell. Within weeks of conception, a simple tube of neural tissue had formed, and from this beginning every thought, movement and feeling you have ever had began to take shape. This early structure is called the neural tube. It closes along its length and then swells at one end, creating bulges that go on to form the major regions of the brain.
These bulges divide into three primary regions, forming in order from the front of the tube to the back: the forebrain, the midbrain and the hindbrain. Each region later develops into more specialised structures, but the front-to-back order in which they first appear is the same in every human embryo, whatever environment that person grows up in.
The developing brain grows from a neural tube that swells into three primary regions, in this order: forebrain, midbrain and hindbrain. The hindbrain later gives rise to two further structures — the cerebellum and the medulla — which is why the specification lists five structures in total.
The Forebrain
The forebrain is the largest of the three primary regions. It grows into the parts of the brain used for reasoning, language, memory, sensory processing and emotional control. Sitting at the very front of the developing brain, it eventually forms the outer wrinkled layer most people picture when they think of ‘the brain’, along with deeper structures that relay information and regulate mood.
The forebrain also develops for the longest period of any brain region. Parts of it, particularly the areas involved in planning and decision-making, are not considered fully mature until a person reaches their mid-twenties. Because it matures so slowly, the forebrain is the region most open to being shaped by a person’s experiences and environment after birth.
The Midbrain
The midbrain sits between the forebrain and the hindbrain. It is smaller than the other two regions but plays a vital connecting role, relaying sensory information — particularly visual and auditory signals — and motor commands between the forebrain and the rest of the nervous system. The midbrain also helps control alertness, eye movement and reflex responses to sudden sounds or bright light.
The Hindbrain
The hindbrain forms at the back of the developing brain, closest to the spinal cord. It develops into two structures the specification requires you to know by name: the cerebellum and the medulla. Together, these keep the body alive and moving long before the forebrain has developed enough to support conscious thought.
The cerebellum coordinates movement and balance. When a baby learns to sit up, crawl and eventually walk, the cerebellum is doing the heavy lifting, gradually turning stumbling, uncoordinated attempts into smooth, controlled movement. Skills such as riding a bike, catching a ball or writing neatly all depend on it.
The cerebellum continues developing well after birth, which is one reason babies cannot walk in their first weeks of life. Damage to the cerebellum in adulthood causes problems with balance and coordination rather than with memory or reasoning, showing how specific its function is compared with the forebrain.
The medulla (sometimes called the medulla oblongata) sits at the very base of the brain, where it joins the spinal cord. It controls autonomic functions — processes the body carries out automatically, without any conscious effort. Breathing, heart rate, blood pressure and swallowing are all regulated here, along with reflexes such as coughing and sneezing.
Because these functions are essential for staying alive, the medulla is fully functional from the moment a baby is born. This is why a newborn can breathe, cry and swallow immediately, even though the forebrain regions responsible for conscious thought are still years away from maturity.
Five named structures matter here: the forebrain (higher thinking, sensory processing, emotion), the midbrain (relaying sensory and motor signals, alertness), the hindbrain (connects the brain to the spinal cord) and, developing from the hindbrain, the cerebellum (movement and balance) and the medulla (automatic survival functions such as breathing and heart rate).
The sequence in which these five structures form — forebrain, midbrain and hindbrain appearing first, with the cerebellum and medulla developing from the hindbrain — is the same in every human embryo. This points to the influence of nature: genes direct the basic blueprint of brain structure, ensuring the same regions form in the same order in every person.
But structure is not the whole story. The nurture side of the debate points out that connections between neurons are strengthened or weakened depending on the experiences a person has, particularly within the slowly maturing forebrain. A region can be present and working at birth, as the medulla is, while a different region is still being shaped over years by how it is used.
Most psychologists accept that early brain development reflects an interaction of both nature and nurture: genes set out the basic regions and the order in which they appear, while experience after birth fine-tunes how the more slowly developing structures, especially the forebrain, come to function.