The birth of a thought

The brain is a truly fascinating organ. It operates at lightning speed, controlling every aspect of our lives, keeping all activities under a strict watch. All of that in a 1.3 kilograms of highly functioning jelly. How it comes to be such a construct is a story of everybody's lifetime!

This article leans heavily on previous knowledge gathered in preceeding articles about neurons, astrocytes, oligodendrocytes and microglia. It is highly recommended to explore them first, for a better reading pleasure. Due to the complexity and volume of the topic, it will be covered in two articles.

The brain matter indeed is very similar in both texture and density to a block of jelly, locked away behind the skull like a criminal, in a location superior to other organs. The skull, in some more dense than in others, provides ample protection to our jelly block from outside hazards. Contrary to popular beliefs, the brain isn't attached to the skull almost anywhere. Rather, it floats in a thin layer of liquid that functions as both insulation and buoyantic fluid, working 24/7, scheming to keep us alive. And, for the most part, doing it rather well, with the help of all other organs. Or, to be more precise, because all other organs, who were all developed to either prolong the life of the brain, or to replicate and enhance it. There is a thought to think over.

How can we do that? How can we – think? How can we form thoughts, remember, plan and solve complex mathematical problems, write articles and research the very organ we research with? How is a thought birthed, how is a decision being made?

Any individual claiming to know the definite answer to these questions might want to contact https://www.nobelprize.org/ for further inquiries. You might be eligible!

It all starts with a bang

To discuss the birth of thoughts is to discuss brain development, both through biological and personal history. The secret to it lies somewhere in the very beginnings of human development, several hours after successful sex, right at the time of fertilization.

Every human life starts from a single unified cell when a sperm cell fertilizes an egg cell. The union of the two is called a zygote, and it starts rapidly dividing, with not much differences between it and a tumor. After a period of time, the conglomerate of cells forms a partially hollow sphere the size of a pin head called gastrula. From there, three distinct cell lines can be seen: endodem, ectoderm and mesoderm. The endoderm gives rise to most of the internal organs such as lungs and liver. The mesoderm evolves into the skeletal system, muscles and the vascular system, while the ectoderm forms the skin, and both the central and the peripheral nervous systems.

Development of a zygote into a gastrula, with its three distinct layers.

At this stage, our brain is the equivalent of a LED light equipped with a power source and a switch.

Further cell division gives rise to more complex forms, and a critical mass of cells in a part of the ectoderm called the neural plate prompts the formation of the neural tube. This is the precursor of our brain and the spinal cord.

Formation of the neural tube.

The formation of the tube from the neural plate most probably arises due to the critical mass of cells who were displeased to live in a two-dimensional plate instead of in a three-dimensional tube. It might not sound scientific, but most of the primal stimuli and incentives for change occur due to physical limitations of space. Neural tube formation is a good example of a sheet of paper being cramped together into folds.

The formation of our brain has always fascinated humans, especially the field of research. We are still far from having penetrated all the mysteries of this block of jelly locked behind bone bars. And yet, we are slowly learning and discovering its history: wiring like a computer, the discovery of the first sensations, the birth and finally the exploration. All of it is a story to follow!

References:

1.     Dekaban, A.S. and Sadowsky, D., Changes in brain weights during the span of human life: relation of brain weights to body heights and body weights, Ann. Neurology, 4:345-356, 1978

2.     Hepper, P., "Unraveling our beginnings", The Psychologist, 18:474-477, 2005.

3.     Huttenlocher PR, Dabholkar AS. Regional differences in synaptogenesis in human cerebral cortex. The Journal of Comparative Neurology. 1997; 387:167–178. [PubMed: 9336221]

4.     Saladin, K (2011). Anatomy & physiology : the unity of form and function (6th ed.). McGraw-Hill. p. 541. ISBN 9780073378251.

5.     Kandel, Eric R. (2006). Principles of neural science (5. ed.). Appleton and Lange: McGraw Hill. ISBN 978-0071390118.

6.     Tierney A. L., Nelson C. A. Brain Development and the Role of Experience in the Early Years. Zero Three. 2009 November 1; 30(2): 9–13.

7.     BrainConnection.com [no longer in function]