The Neurosciences and Their Evolution Over Time

Neuroscience is made up of a group of scientific disciplines focused on the study of the nervous system. It is composed of the central nervous system and the peripheral nervous system. One of the primary objectives pursued by the neurosciences is to understand the mechanisms of regulation and control of nervous reactions; as well as brain function.

Dr. Ángeles Castro explains the evolution of neuroscience over time and its contribution to science.

The brain and the neurosciences

The brain as a control system is currently studied by the neurosciences. Its development began in the time of the Greeks and continues to evolve to the present. The human body is a complex network of nervous networks that are controlled by the brain. Every day, millions of neurons remain continuously connected, transmitting impulses with specific information to each organ of the body.

The brain is an extremely complex structure and several properties of its functioning are still unknown. However, research carried out by the neurosciences has made it possible to deepen our understanding of the structure, function, and importance of the nervous system.

Importance of the neurosciences

Among the most important aspects of the neurosciences is the study of individuals’ learning capacity, which is directly associated with the ability to survive. Beyond Darwin’s theory of evolution, the brain was used to a greater or lesser extent for learning. From gathering food, making fire, hunting, settling and establishing activities to live; to reaching the industrial revolutions and the development of artificial intelligence.

Certainly, all of this has been possible through learning, which is linked to the refinement of brain functions and the efficiency of neuronal interactions. These factors are studied in detail by the neurosciences.

On the other hand, in this decade of the 21st century, the neurosciences are experiencing integration with other fields of knowledge. For example: embryology, physiology, biochemistry, pharmacology, psychology, neurology, bioengineering, computer science and artificial intelligence.

Historical background of the neurosciences

First contacts with the neurosciences

In Greece in the 5th century BC, Alcmeon of Croton described the optic nerves that he located during dissections he carried out. In his descriptions he proposed that the brain was the seat of thought and sensations.

Similarly, the Corpus Hipocraticum stated: “men should know that joys, delights, sorrows, griefs and lamentations come from the brain and from no other place. And thus, in a special way we acquire wisdom and knowledge, we see, we hear and we know what is absurd and what is right, what is bad and what is good, what is sweet and what is repugnant… And by the same organ we become mad and delirious, and fears and terrors assail us…we suffer all these things because the brain is not healthy…I am of the opinion that in these ways the brain exerts the greatest power over man”.

On the other hand, Aristotle subscribed to the idea that the center of intellect resided in the heart; he held that the rational nature of man was due to the brain’s capacity to cool the overheated blood of the heart.

Later, Galen, based on the thesis of Hippocrates and on the structural differences between the brain and the cerebellum, proposed that the cerebellum acted on the muscles. He also proposed that it was the receiver of sensations and preserved memory. In addition, he related the cerebral ventricles to the cavities of the heart, establishing that sensations and movements depended on the flow of humors to or from the cerebral ventricles through the nerves.

The neurosciences in the 18th century

In this period it was proposed that nervous tissue performed a glandular function. Based on Galen’s theory it was established that the nerves were the channel that transported the fluids secreted by the brain and spinal cord to the periphery of the human organism.

Regarding cerebral anatomy, Vesalius revealed several details. However, the concept of ventricular localization and cerebral functions remained unchanged. Similarly, the invention of hydraulic machines helped reinforce the ventricular theory of the brain. This theory states that: “the fluids expelled from the ventricles pump the body, which is why the muscles increase in size during movement”.

Correlatively, René Descartes defended the mechanistic theory of brain function to explain animal behavior. However, this did not explain the complexity of human behavior because the individual possesses intellect and a soul given by God. Descartes firmly believed that the brain controls human behavior in what is animal in it, and that the special capacities of man reside outside, in the mind (“l’esprit”).

From this theory two lines of thought arose that persist today. On the one hand, the mechanistic philosophy that interprets the body as a machine and as such must be analyzed, including the brain. On the other hand, the mind-body line, which is shared by some neuroscientists.

The neurosciences in the 19th and 20th centuries

The emergence of the neurosciences had as their starting point the discoveries of Santiago Ramón y Cajal, who studied proteins and neurons as the basis of the cellular structure of the brain. Regarding neurons, he contributed that: “the nervous system is formed by independent cells: the neurons, which contact each other at specific places”.

Likewise, Ramón y Cajal created a new neuroanatomical theory and described neuronal structure. He also established the mechanisms that govern them, the development, degeneration, and generation of the nervous system. These elements constitute the foundations of the neurosciences today.

The improvement of the neurosciences would have been difficult without advances in neurophysiology, a science that emerged at the end of the 18th century with Galvani’s research on the influence of electricity on the activity of the cells that make up muscle tissue.

The neuronal theory was confirmed through various studies, including that carried out by Ross Harrison, an embryologist who, through tissue cultures, corroborated the theory and demonstrated that the extensions of neurons, the dendrites and axons, are continuous structures of the neuronal body and develop from it.

More advanced discoveries

Later, during the 19th century, scientists Emil Du Bois-Reymond, Johannes Müller and Hermann von Helmholtz developed the foundations of electrophysiology. In addition, Helmholtz discovered the electrical activity of neurons during the transmission of information between cells.

In the same line of research, physician Charles Bell and physiologist François Magendie clarified the route of signal transmission between the nervous system and the periphery of the organism. On the other hand, neurophysiologist Charles Scott emphatically confirmed Ramón y Cajal’s theory about interneuronal contact, which he called the synapse.

At the end of the 19th century, pharmacology began to develop and gained greater interest when Claude Bernard, Paul Ehrlich and John Langley demonstrated that drugs interact with specific cellular receptors. This discovery forms the basis for current studies on chemical synaptic transmission. Later, around 1960, biochemist Hornykiewicz observed that the brains of people with Parkinson’s disease showed a low concentration of dopamine. In this way, a pathophysiological correlation was established between the deficit of a neurotransmitter and the presence of a neurological disorder.

Recent years

In recent years, the development of the neurosciences has been linked with psychology, a discipline that has been present in society since the Greek era with the same questions about the nature of the mind and human behavior.

Conclusion

Finally, it is established that the neurosciences are in continuous evolution, such that the proposals and the confirmation of various hypotheses have led to significant discoveries for understanding the brain’s structure. Likewise, the multidisciplinary approach that characterizes them allows investigation into various aspects to answer questions related to the specific functioning of the nervous system and each of its components.

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Las neurociencias y su evolución en el tiempo