Neuroscience is a group of scientific disciplines focused on the study of the nervous system. This is formed by the central nervous system and the peripheral nervous system. One of the main objectives of neuroscience is to understand the mechanisms of regulation and control of nervous reactions, as well as brain function.
Dr. Ángeles Castro explains the evolution of neurosciences through time and their contribution to science.
Brain and neurosciences
The brain as a control system is currently studied by neurosciences. Its evolution began since the time of the Greeks and continues to develop to this day. The human body is a complex web of nerve networks that are controlled by the brain. Every day, millions of neurons are continuously connected, transmitting impulses with specific information to each organ of the body.
The brain is a highly complex structure and several properties of its functioning are still unknown. However, neuroscience research has allowed us to delve deeper into the structure, function and importance of the nervous system.
Importance of neurosciences
Among the most important aspects of neuroscience is the study of the learning capacity of individuals, 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 to learn. From gathering food, making fire, hunting, settling down and implementing activities to live; to the industrial revolutions and the development of artificial intelligence.
Certainly, all this has been possible through learning, which is linked to the improvement of brain functions and the efficiency of neuronal interactions. These factors are studied in detail by the neurosciences.
Moreover, in this decade of the 21st century, 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 neurosciences
First contacts with neurosciences
In Greece in the 5th century BC. Alcmeon of Crotona made the description of the optic nerves that he located during dissections that he carried out. In his descriptions he proposed that the brain was the seat of thought and sensation.
Similarly, Corpus Hippocraticum pointed out: “men should know that joys, joys, sorrows, afflictions and lamentations proceed from the brain and from nowhere else. And so in a special way we acquire wisdom and knowledge, we see, hear and know what is absurd and what is right, what is evil and what is good, what is sweet and what is disgusting…And by the same organ we become mad and delirious, and fears and terrors assail us…we suffer all these things from the brain when it is not healthy…I am of the opinion that in these ways the brain exercises the greatest power over man.”
On the other hand, Aristotle participated in the idea that the center of the intellect resided in the heart, he held that the rational nature of man was due to the brain’s ability to cool the overheated blood of the heart.
Later, Galen, based on Hippocrates‘ thesis and on the structural difference between the brain and the cerebellum, proposed that the cerebellum acted on the muscles. He also proposed that it was the receptor of sensations and conserved memory. In addition, he related the cerebral ventricles with 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.
Neurosciences in the 18th century
In this period it was proposed that nerve tissue performed a glandular function. Based on Galen’s theory, it was established that the nerves were the conduit that transported the fluids secreted by the brain and spinal cord to the periphery of the human organism.
With respect to brain anatomy, Vesalius revealed several details. However, the concept of ventricular location and brain functions remained unchanged. Similarly, the invention of hydraulic machines contributed to reinforce the cerebral ventricular theory. This theory states that: “the liquids expelled from the ventricles pump the organism, 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 God-given soul. Descartes firmly believed that the brain controls human behavior as far as it is animal and that man’s special capacities reside outside, in the mind (“l’esprit”).
Based on this theory, two lines of thought emerged that survive 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.
Neurosciences in the 19th and 20th centuries
The emergence of neurosciences had as its 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: neurons, which contact each other in specific places”.
Likewise, Ramón y Cajal created a new neuroanatomical theory and described the neuronal structure. In addition, he established the mechanisms that govern them, the development, degeneration and generation of the nervous system. These elements constitute the foundations of neurosciences today.
The improvement of neurosciences would be difficult without the advance of 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 constituent cells of muscle tissue.
The neuronal theory was confirmed through various studies, among them the one carried out by Ross Harrison. An embryologist who, by means of tissue cultures, corroborated the theory and demonstrated that the prolongations of neurons, dendrites and axons, are continuous structures of the neuronal body and develop from it.
More advanced findings
Later in the 19th century, scientists Emil Dubois-Reymnd, Johannes Muller and Herrmann von Helmholtz developed the fundamentals of electrophysiology. In addition, Helmholtz discovered the electrical activity of neurons during the transmission of information between cells.
In the same line of research, the physician Charles Bell and the physiologist Francois Magendie clarified the signal transmission pathway between the nervous system and the periphery of the organism. On the other hand, the neurophysiologist Charles Scott strongly confirmed Ramon y Cajal’s theory of interneuronal contact, which he called synapse.
At the end of the 19th century, pharmacology began to develop and became more interesting when Claude Berenard, Paul Ehrlich and John Langley demonstrated that drugs interact with specific cell receptors. This discovery forms the basis for current studies on synaptic chemical transmission. Subsequently, around 1960, the biochemist Hornykiewicz observed that the brains of people with Parkinson’s disease showed a low concentration of dopamine. Thus, a pathophysiological correlation was established between the deficit of a neurotransmitter and the presence of a neurological disorder.
In recent years, the development of neurosciences has been linked to psychology. This discipline has been present in society since Greek times with the same questions about the nature of the mind and human behavior.
Finally, it is established that neurosciences are in continuous evolution, in such a way that the approaches and the confirmation of diverse hypotheses have led to relevant discoveries to understand the brain structure. Likewise, the multidisciplinary approach that characterizes them allows investigating different aspects to answer questions related to the specific functioning of the nervous system and each of its components.