Neuropsychology

In ancient Egypt, writings on medicine date from the time of the priest Imhotep.[5] They took a more scientific approach to medicine and disease, describing the brain, trauma, abnormalities, and remedies for reference for future physicians. Despite this, Egyptians saw the heart, not the brain, as the seat of the soul.[6]

Senses, perception, memory, dreams, action in Aristotle's biology. Impressions are stored in the seat of perception, linked by his Laws of Association (similarity, contrast, and contiguity).[7]

Aristotle reinforced this focus on the heart which originated in Egypt. He believed the heart to be in control of mental processes, and looked on the brain, due to its inert nature, as a mechanism for cooling the heat generated by the heart.[8][9] He drew his conclusions based on the empirical study of animals. He found that while their brains were cold to the touch and that such contact did not trigger any movements, the heart was warm and active, accelerating and slowing dependent on mood.[8][9] Such beliefs were upheld by many for years to come, persisting through the Middle Ages and the Renaissance period until they began to falter in the 17th century due to further research.[9] The influence of Aristotle in the development of neuropsychology is evident within language used in modern day, since we "follow our hearts" and "learn by the heart."[9]

Hippocrates viewed the brain as the seat of the soul. He drew a connection between the brain and behaviors of the body, writing: "The brain exercises the greatest power in the man."[10] Apart from moving the focus from the heart as the "seat of the soul" to the brain, Hippocrates did not go into much detail about its actual functioning. However, by switching the attention of the medical community to the brain, his theory led to more scientific discovery of the organ responsible for our behaviors. For years to come, scientists were inspired to explore the functions of the body and to find concrete explanations for both normal and abnormal behaviors. Scientific discovery led them to believe that there were natural and organically occurring reasons to explain various functions of the body, and it could all be traced back to the brain. Hippocrates introduced the concept of the mind – which was widely seen as a separate function apart from the actual brain organ.

Philosopher René Descartes expanded upon this idea and is most widely known for his work on the mind–body problem. Often Descartes's ideas were looked upon as overly philosophical and lacking in sufficient scientific foundation. Descartes focused much of his anatomical experimentation on the brain, paying special attention to the pineal gland – which he argued was the actual "seat of the soul." Still deeply rooted in a spiritual outlook towards the scientific world, the body was said to be mortal, and the soul immortal. The pineal gland was then thought to be the very place at which the mind would interact with the mortal and machine-like body. At the time, Descartes was convinced the mind had control over the behaviors of the body (controlling the person) – but also that the body could have influence over the mind, which is referred to as dualism.[11] This idea that the mind essentially had control over the body, but the body could resist or even influence other behaviors, was a major turning point in the way many physiologists would look at the brain. The capabilities of the mind were observed to do much more than simply react, but also to be rational and function in organized, thoughtful ways – much more complex than he thought the animal world to be. These ideas, although disregarded by many and cast aside for years led the medical community to expand their own ideas of the brain and begin to understand in new ways just how intricate the workings of the brain really were, and the complete effects it had on daily life, as well as which treatments would be the most beneficial to helping those people living with a dysfunctional mind. The mind–body problem, spurred by René Descartes, continues to this day with many philosophical arguments both for and against his ideas. However controversial they were and remain today, the fresh and well-thought-out perspective Descartes presented has had long-lasting effects on the various disciplines of medicine, psychology, and much more, especially in putting an emphasis on separating the mind from the body in order to explain observable behaviors.

Thomas Willis

It was in the mid-17th century that another major contributor to the field of neuropsychology emerged. Thomas Willis studied at Oxford University and took a physiological approach to the brain and behavior. It was Willis who coined the words 'hemisphere' and 'lobe' when referring to the brain.[12] He was one of the earliest to use the words 'neurology' and 'psychology'. Rejecting the idea that humans were the only beings capable of rational thought, Willis looked at specialized structures of the brain.[9] He theorized that higher structures accounted for complex functions, whereas lower structures were responsible for functions similar to those seen in other animals, consisting mostly of reactions and automatic responses.[13] He was particularly interested in people with manic disorders and hysteria.[14][15] His research constituted some of the first times that psychiatry and neurology came together to study individuals. Through his in-depth study of the brain and behavior, Willis concluded that automated responses such as breathing, heartbeats, and other various motor activities were carried out within the lower region of the brain. Although much of his work has been made obsolete, his ideas presented the brain as more complex than previously imagined, and led the way for future pioneers to understand and build upon his theories, especially when it came to looking at disorders and dysfunctions in the brain.[14]

Neuroanatomist and physiologist Franz Joseph Gall made major progress in understanding the brain. He theorized that personality was directly related to features and structures within the brain. However, Gall's major contribution within the field of neuroscience is his invention of phrenology. This new discipline looked at the brain as an organ of the mind, where the shape of the skull could ultimately determine one's intelligence and personality.[16] This theory was like many circulating at the time, as many scientists were taking into account physical features of the face and body, head size, anatomical structure, and levels of intelligence; only Gall looked primarily at the brain. There was much debate over the validity of Gall's claims however, because he was often found to be wrong in his predictions. He was once sent a cast of René Descartes' skull, and through his method of phrenology claimed the subject must have had a limited capacity for reasoning and higher cognition.[17] As controversial and false as many of Gall's claims were, his contributions to understanding cortical regions of the brain and localized activity continued to advance understanding of the brain, personality, and behavior. His work is considered crucial to having laid a firm foundation in the field of neuropsychology, which would flourish over the next few decades.

Jean-Baptiste Bouillaud

Towards the late 19th century, the belief that the size of ones skull could determine their level of intelligence was discarded as science and medicine moved forward. A physician by the name of Jean-Baptiste Bouillaud expanded upon the ideas of Gall and took a closer look at the idea of distinct cortical regions of the brain each having their own independent function. Bouillaud was specifically interested in speech and wrote many publications on the anterior region of the brain being responsible for carrying out the act of ones speech, a discovery that had stemmed from the research of Gall. He was also one of the first to use larger samples for research although it took many years for that method to be accepted. By looking at over a hundred different case studies, Bouillaud came to discover that it was through different areas of the brain that speech is completed and understood. By observing people with brain damage, his theory was made more concrete. Bouillaud, along with many other pioneers of the time made great advances within the field of neurology, especially when it came to localization of function. There are many arguable debates as to who deserves the most credit for such discoveries,[18] and often, people remain unmentioned, but Paul Broca is perhaps one of the most famous and well known contributors to neuropsychology – often referred to as "the father" of the discipline.

Inspired by the advances being made in the area of localized function within the brain, Paul Broca committed much of his study to the phenomena of how speech is understood and produced. Through his study, it was discovered and expanded upon that we articulate via the left hemisphere. Broca's observations and methods are widely considered to be where neuropsychology really takes form as a recognizable and respected discipline. Armed with the understanding that specific, independent areas of the brain are responsible for articulation and understanding of speech, the brains abilities were finally being acknowledged as the complex and highly intricate organ that it is. Broca was essentially the first to fully break away from the ideas of phrenology and delve deeper into a more scientific and psychological view of the brain.[19]

Carl Wernicke was an influential nineteenth century neuropsychiatrist specifically interested in understanding how abnormalities could be localized to specific brain regions. Previously held theories attributed brain function as one singular process but Wernicke was one of the first to attribute brain function to different regions of the brain based on sensory and motor function.[20] In 1873, Wernicke observed a patient presenting with poor language comprehension despite maintaining intact speech and hearing following a severe stroke. Post-morbid analysis revealed a lesion near the auditory region of the brain in the parietal-temporal region of the left hemisphere.[21] Originally named sensory aphasia, this region later became known as Wernicke's area.[21] Individuals with damage to this area present with fluent but receptive aphasia characterized by the inability to comprehend or express written or spoken language while maintaining intact speech and auditory processes.[22] Along with Paul Broca, Wernicke's contributions greatly expanded the present knowledge of language development and localization of left hemispheric function.

Lashley's works and theories that follow are summarized in his book Brain Mechanisms and Intelligence.[23] Lashley's theory of the Engram was the driving force for much of his research. An engram was believed to be a part of the brain where a specific memory was stored. He continued to use the training/ablation method that Franz had taught him. He would train a rat to learn a maze and then use systematic lesions and removed sections of cortical tissue to see if the rat forgot what it had learned.

Through his research with the rats, he learned that forgetting was dependent on the amount of tissue removed and not where it was removed from. He called this mass action and he believed that it was a general rule that governed how brain tissue would respond, independent of the type of learning. But we know now that mass action was a misinterpretation of his empirical results, because in order to run a maze the rats required multiple cortical areas. Cutting into small individual parts alone will not impair the rats' brains much, but taking large sections removes multiple cortical areas at one time, affecting various functions such as sight, motor coordination, and memory, making the animal unable to run a maze properly.[24]

Lashley also proposed that a portion of a functional area could carry out the role of the entire area, even when the rest of the area has been removed. He called this phenomenon equipotentiality. We know now that he was seeing evidence of plasticity in the brain: within certain constraints the brain has the ability for certain areas to take over the functions of other areas if those areas should fail or be removed - although not to the extent initially argued by Lashley.