Three to four weeks after conception, one of the two cell layers of the human embryo, which is about one-tenth of an inch long at this moment, starts to thicken and build up in the middle. In this way, a flat neural plate grows and parallel ridges are being formed, rising across the surface. A few days later, these ridges fold in towards each other and fuse to form the hollow neural tube. The top of this tube grows thicker and gives rise to three bulges that will grow into the hindbrain, midbrain and forebrain. Later, the first signs of the eyes and the brain hemispheres appear.

Similarities and Differences

Many of the mechanisms of brain development still remain secrets. However, neuroscientists are beginning to uncover some of these complex steps through the studies of the roundworm, fruit fly, frog, zebrafish, mouse, rat, chicken, cat and monkey brain development.

A lot of initial steps in brain development are similar across species, while later steps tend to be different. Through the study of these similarities and differences, scientists can learn how the brain develops and how brain abnormalities can be prevented or treated.

Networking Neurons

Initially produced along the central canal in the neural tube, neurons migrate from their birthplace to their final destination in the brain. Collecting together, they form each of the various brain structures and acquire specific ways of transmitting nerve messages. Their axons grow a long distance to find and connect with appropriate partners, thereby forming elaborate and specific circuits. The last step is the elimination of redundant or improper connections, thereby honing the specific purposes of the circuit that remains. All this results in an accurate and elaborate network of 100 billion adult neurons capable of body movement, perception, emotion and thought.

Understanding the Brain

Knowing how the brain is build, step by step, is essential for understanding its ability to reorganize in response to external influences or injury. Studies in this field can also shed light on brain functions such as learning and memory. A failure to construct proper connections during development is thought to result in brain disorders such as schizophrenia and mental retardation.

Now, neuroscientists are beginning to understand and discover some general principles that will aid in comprehension of the process of brain development, many of which overlap in time. This knowledge will not only contribute to the treatment and cure of many brain disorders, but will also provide us with a deeper understanding of how human beings are able to do what they do.