1.2 History of Neuroscience

The earliest written record representing the brain comes from an ancient Egyptian papyrus (paper-like document) called the Edwin Smith surgical papyrusAn ancient Egyptian text with hieroglyphic writing that talked about anatomy, surgery, and the nervous system., which was likely created about 1700 BC. In hieroglyphic writing, the papyrus discusses different surgical techniques and references the brain, meninges (tissue around the brain), fluid in the brain, and the spinal cord (refer to Figure 1.1) (Feldman & Goodrich, 1999). The Egyptians, however, did not think much of the brain and would remove it through the nostrils during the mummification process. The heart and other organs were considered much more precious, and these organs were preserved in jars and buried with the mummy. Greek philosopher Aristotle (384–322 BC) also thought the heart to be the location of intelligence, and the brain’s primary function was to cool the blood (Gross, 1995). The idea that the heart is at the core of our emotions, love, or “soul” still resonates in our vernacular and metaphors today. However, other ancient Greek philosophers and thinkers like Pythagoras, Hippocrates, and Plato came to recognize that the brain was the seat of mental processes and intelligence (Gross, 1987). A physician in ancient Greece named Galen worked with Hippocrates and created some of the first comprehensive texts of anatomy, and his writings and illustrations were used for over 1300 years. Galen also believed that there was not a difference between the mind and the body, which is a fundamental principle of neuroscience today (Lloyd, 2007).

TrepanationAn ancient practice of drilling holes in the skull. Evidence of this early practice has been found around the world dating back thousands of years. (trephination) is a process of drilling a hole (or holes) into the skull and is one of the oldest documented surgical procedures. Holes were drilled into the skull to relieve built-up pressure, drain pus from infection, or release what were believed to be evil spirits or demons. Evidence of these practices has been found all over the world, including in North America, Asia, Europe, and especially Peru and other areas of South America (Faria, 2015). Skulls with holes were found in a burial site in France that dated back to 6500 BC. As one can imagine, trepanation often resulted in death, either from the practice itself or from subsequent infection. However, it is possible that if the meninges (outer covering of the brain) or blood vessels weren’t damaged, people could survive (Lopez et al., 2011). There is evidence that trepanation continued to be practiced in Europe during the Renaissance (refer to Figure 1.2) and even into modern times, mainly in areas of South America. During the 20th century, there is evidence that this practice continued, as holes were drilled into the side of the skull and sharp metal instruments or chemicals were used to scramble brain tissue. This was done in the frontal lobe as a way to reduce psychosis and other mental disorders (Anastasia, 1984). This practice of “lobotomy” or leucotomy is part of the tragic history of neuroscience and neurosurgery that will be discussed further in Chapter 3 “Neuron Communication”.

The RenaissanceA time in the 14th through 17th centuries where artists and anatomists explored details of the nervous system. is a time of great thinkers, scientists, and artists spanning the 14th and 17th centuries. Leonardo da Vinci (1452–1519) is best known as a painter (Mona Lisa, The Last Supper) and inventor, but he was also an exceptional scientist and illustrator of human anatomy and the nervous system (refer to Figure 1.3). He created a mold of the spaces inside the brain (known as ventricles) by injecting wax into an ox brain, and he hypothesized that the ventricles housed the human soul. He developed theories about the perception of sight and smell and how the brain decodes these sensations (Pevsner, 2002). Paluzzi, Belli, Bain, and Viva (2007) point out that many artists during the Renaissance began depicting cryptic images of the brain in their artwork that may be a representation of the importance of human thought and reason. One of the most famous is Michelangelo’s fresco on the Sistine Chapel’s ceiling called The Creation of Adam (refer to Figure 1.4), which has several characteristics of a longitudinal section of the human brain.

Often artists, medical doctors, and scientists worked together to map out the anatomy of the body and brain. One of the most famous anatomists of the time was Andreas VesaliusAn anatomist who created the most detailed books on anatomy during the Renaissance. (1514–1564), who worked with illustrators like Johan Van Calcar to create the quintessential human anatomy books of the time such as De Humani Corporis Fabrica (On the Fabric of the Human Body). De Fabrica was filled with excellent illustrations of the human body, including the brain and nervous system (refer to Figure 1.5). Before Vesalius, dissecting humans was prohibited in many medical circles, but these rules were discarded as he and his students conducted detailed dissections as a standard part of medical education. His several volumes on anatomy, including one dedicated to nerves, were much improved over Galen’s work from centuries before.

After the Renaissance came the Scientific RevolutionA time in the 17th and 18th centuries when the scientific method and empiricism were having a significant influence on thinkers and philosophers. This period is also known as the Age of Enlightenment. and Age of Enlightenment in the 17th and 18th centuries. During this period, we find great thinkers about science, mathematics, and philosophy such as Francis Bacon, John Locke, David Hume, and René Descartes. This was a time when the scientific method became a way to investigate the world (refer to Chapter 4 “Research Methods: Histology, Imaging, and Stimulating”). It was also the birth of empiricism (epistemology) or the idea that knowledge and understanding begin through sensory experiences of the natural world. A lot can be accomplished when the scientific method and principles of empiricism are applied to investigating how the brain works; it also enables less reliance on leeches, bloodletting, trepanation, and burning at the stake in combating disorders like epilepsy. The thoughts of René Descartes are most relevant to how we think about and approach neuroscience, and most textbooks in biopsychology and psychology address his theory that the mind and the body are separate.

René DescartesA French philosopher known for his ideas that the body worked like a machine with reflexes initiated by fluids. He is also known for his philosophy of dualism. (1596–1650) was a French philosopher and scientist. The machines of the time and mechanical human figures called automatons that were often made by watchmakers influenced Descartes’s thought on the brain and the body. He thought that humans worked in part like machines, with reflexes that reacted to the environment (refer to Figure 1.6). However, essential to Descartes’s theory was the idea that we are governed by two separate “substances”: the material flesh and the nonphysical soul. The soul is the mind and does the thinking and connects to the physical body through a small area of the brain called the pineal gland (refer to Figure 1.6). This philosophy is known as dualismThe idea that the brain (tissue) is different from and is controlled by the mind (spiritual). (dual means two parts) and became an important doctrine. Setting aside the difficulty of explaining how the mechanism of the soul is influencing the body, this was the birth of the mind–body problem. Neuroscientists today, for the most part, have abandoned the idea of dualism for the notion that all psychological processes are a product of nervous system activity. To quote the famous scientist Marvin Minsky, “The mind is what the brain does.” This idea is known as monismThe idea that the mind is a product of brain activity. This is a basic accepted principle in neuroscience today. (mon-, from mono-, means one part). While most psychologists and neuroscientists favor a monistic over a dualistic approach to their field, the issue isn’t completely settled in the purest sense of the terms. We’ll deal with that in Chapter 1, Section 3 “The Many Areas of Biopsychology”.

We will be discussing the work of many researchers in neuroscience in the coming chapters, but here are a few scientists from the last two centuries. The middle and end of the nineteenth century gave us Charles Darwin (1809–1882) and his theory of natural selection to explain the evolution of living organisms. His books and theories connected humans with other animals, physiologically, behaviorally, and mentally (refer to Chapter 5 “Genetics and Evolution”). His theories proposed the idea that humans were not put on the earth in their current form but had evolved, like other creatures, from a common ancestor. Darwin’s theories are the cornerstone of research in biology, genetics, neuroscience, and psychology. We also saw researchers applying the strict experimental methodology to uncover fundamental principles of neuroscience. Wilhelm WundtConsidered the father of modern day experimental psychology. He researched sensation and perception using the scientific method. (1832–1920) was one of the first to start studying the mind (psychology) as a science separate from philosophy, religion, or biology. Wundt was considered the first experimental psychologist, and he conducted systematic investigations of the physiology of senses and perception. Russian physiologist Ivan Pavlov (1849–1936) received a Nobel Prize in Physiology or Medicine for his work on the digestive system using dogs as model animals. He then focused on how his understanding of physiology applied to basic principles of learning and memory (refer to Chapter 4 “Research Methods: Histology, Imaging, and Stimulating”).

In the late 1800s, Camillo Golgi and Franz Nissl were developing techniques for staining and identifying the cells in the brain (neurons), enabling researchers to begin theorizing about how neurons communicated and reacted to external and internal stimuli. This set the stage for modern neurohistology (the study of brain tissue), and Golgi’s and Nissl’s staining techniques are still being used today. Santiago Ramón y Cajal was an artist and physiologist who modified Golgi’s methods to create detailed images of nervous tissue, which he illustrated (refer to Figure 1.7). Cajal is considered the father of modern-day neuroscience, and he and Golgi later shared a Nobel Prize for their work in 1906 (refer to Chapter 4 “Research Methods: Histology, Imaging, and Stimulating”). Around the same time, researchers became overly fascinated with measuring the size of skulls and attributing human characteristics (intelligence, laziness, and the like) with the size and shape of the head. This pseudoscience of craniometry led to problems of classism, discrimination, and racism, as well as the advent of another pseudoscience called phrenologyA movement in the late 1800s and early 1900s that stated aspects of a person’s personality, emotions, and intelligence could be determined by measuring bumps on the skull. The practice has been discredited as pseudoscience., which assumes that specific areas of the brain predict certain mental traits and measures the bumps on a person’s skull. There were schools and journals dedicated to phrenology (refer to Figure 1.8), and a professional phrenologist would read a person’s skull like a fortunate teller reads someone’s palm. While likely as accurate as palm readers, phrenologists and craniometrists would boast of the strength of their scientific support.

Throughout this book, we’ll discuss many of the more recent advances in neuroscience and the people behind these discoveries. But, we’ll also see how lessons of the past are crucial in understanding contemporary research around the issues of innovation, discoveries, and ethics.

This textbook is mostly about modern advancements in neuroscience and their application to understanding mental processes and behavior. The incredible speed of computers has given researchers the ability to image and analyze the brain’s activity. The field of genomics has created tools to not only sequence and map the human genome (our DNA) but also manipulate and engineer the DNA of many animals and plants with relative ease. This incredible understanding of genetics has given us a window into how our genes work with our experiences in altering behaviors, contributed to our understanding of mental disorders, and made it possible to design personalized treatments. We also talk about how breakthroughs in psychopharmacology have relieved symptoms of schizophrenia, depression, anxiety, epilepsy, sleep problems, pain, and many other mental and physical health problems. Modern technologies have also allowed large-scale collaborations between research institutes around the world to tackle big problems like mapping the brain’s connections or identifying the genes (DNA sequences) that contribute to depression, schizophrenia, or Alzheimer’s disease (Wang et al., 2018). Finally, researchers are also connecting microprocessors and computers with brain tissue that can return sight to a person with visual impairment, allow someone with a spinal cord injury to walk again, or permit someone to move robotics with their thoughts (Shih et al., 2012). It’s an exciting time to learn about and be involved in neuroscience.