Introduction to Neurology PDF

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© VeraPetruk/Getty Images CHAPTER 1 All rights reserved. May not be reproduced in any form without permission from the publisher, except fair uses permitted under U.S. or applicable copyright law. Introduction to Neurology CHAPTER OUTLINE CHAPTER PREVIEW Introduction: Defining Neurology In this chapter we will begin our journey into the world of neuroscience. We will define important terms, like neurology, to help The Need for Neurological Training us begin to frame this world. We will then make a case on why it A Broad Overview of the Nervous is important for a speech-­language pathologist and audiologist to System have a working knowledge of the nervous system. Lastly, we will The Nervous System Is a Precious examine theoretical perspectives and technologies that speak to the Resource question: How does the brain work? What Does Neurology Mean to Me? Famous People With Neurological Conditions IN THIS CHAPTER Prevalence, Incidence, and Cost of Neurological Disorders In this chapter, we will... Classification of Neurological Disorders Define the term neurology A Brief History of Neuroscience Discuss why speech-­language pathologists and Prehistory audiologists need to know and understand neurology Early History Discuss why the neurological system is a precious resource Later History Answer the question: What does neurology mean to me? Modern History Define the terms function, activity, and participation barriers Neuroscience Today Survey examples of famous people who have suffered Structural Imaging Techniques neurological conditions Functional Imaging Techniques Examine statistics concerning neurological disorders Combined Structural and Functional List various categories of neurological disorders Imaging Techniques Which Test When? Discuss basic theoretical perspectives as to how the brain A Caution Regarding Imaging works Techniques Survey important researchers in the history of Conclusion Copyright 2020. Jones & Bartlett Learning. neuroscience Summary of Learning Objectives Compare and contrast neuroimaging techniques Discuss why these theoretical perspectives matter to fields Key Terms associated with communication sciences and disorders Draw It to Know It Questions for Deeper Reflection Case Study Suggested Projects References EBSCO Publishing : eBook Collection (EBSCOhost) - printed on 12/16/2020 8:26 AM via PACIFIC UNIV 3 AN: 1986080 ; Matthew H Rouse.; Neuroanatomy for Speech-Language Pathology and Audiology Account: s8865459.main.ehost  4 Chapter 1 Introduction to Neurology LEARNING OBJECTIVES 1. The learner will define the following terms: neurology, anatomy, physiology, and pathology. 2. The learner will be able to create an argument as to why speech-­language pathologists and audiologists need neurological training. 3. The learner will be able to list various categories of neurological disorders and provide one example in each category. 4. The learner will be able to draw and explain the spectrum of belief as to how the brain works. 5. The learner will list and define structural and functional imaging techniques and list at least one reason why communication disorders professionals should know about neuroimaging techniques. ▸▸ Introduction: Defining then the various nerves (FIGURE 1-­1). The purpose of this chapter is to give a broad overview of the ner- Neurology vous system as well as a brief survey of neuroscience’s ­history and the important figures in that history. This We begin our journey into the human nervous system chapter also explores modern neuroimaging tech- with this question from the anthropologist Stephen niques that have led to a better understanding of the Juan: “Have you ever wondered about how fantastic brain and how it works. the human brain really is? Every thought, every action, every deed relies upon this incredible organ. Although we take the brain for granted, we couldn’t wonder with- Brain out it” (Juan, 1998, p. 1). The brain is the vehicle we use to wonder. It includes not only the brain but also those other parts of the neurological system that pertain to communication. Neurology is simply the study of the Spinal cord anatomy, physiology, and pathology of the nervous sys- tem. Anatomy is the study of structure, physiology is the study of function or structures in motion, and pathology is the study of disease processes that affect both anatomy and physiology. Put the prefix neuro- in Nerves front of each of these words and you get distinct yet highly related fields of study. Neuroanatomy is the study of the nervous system’s structure. A neuroana- tomical topic is a neuron (i.e., a nervous system cell) and its structure. When we want to talk about how a neuron functions, we have just entered into the area of neurophysiology. The study of nervous system dis- eases is called neuropathology. An example of neu- ropathology would be amyotrophic lateral sclerosis, or Lou Gehrig disease, which affects both the anatomy and physiology of neurons and leads to serious neurologi- cal problems. There are other fields in addition to these, including neurosurgery (removal of structures that impair normal nervous system functioning), neurora- diology (use of radiation therapy for nervous system tumors), and neuroembryology (normal and patholog- ical development of the nervous system). The nervous system is a series of organs that make communication between the brain and body possible in order for us to interact with the world around us. It is through the nervous system’s connec- tions to the body (and vice versa) that we think, feel, and act. The most well-­known organ of the nervous FIGURE 1-­1 The brain, spinal cord, and nerves are the major system is the brain, followed by the spinal cord and components of the human nervous system. EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  A Broad Overview of the Nervous System 5 ▸▸ The Need for Neurological SLPs and audiologists must do their part in fos- tering good relationships with neurologists and other Training doctors; one important way of gaining their col- leagues’ respect is by being excellent at what they do. Why should a speech-­language pathologist (SLP) or Nothing elicits respect like a job well done. Though audiologist be concerned about the anatomy, physiol- SLPs and audiologists are autonomous profession- ogy pathology of the nervous system? What difference als (i.e., they are not supervised by neurologists or does this knowledge make to clinical practice? other doctors), they depend on neurologists for many Rubens (1977), a neurologist, outlined several rea- things, such as referrals and important neurological sons why SLPs and audiologists should know about information on the patient (LaPointe, 1977). Tending neuroscience and neurology. First, he argued that to their relationships with these physicians not only these professionals should know how to speak the helps SLPs and audiologists in these areas, but also language of neurology so that they and neurologists ultimately helps patients receive the important and could better communicate. Neurologists have their specialized services that only SLPs and audiologists own language. When communication disorders pro- can provide. I often tell my students that no one— fessionals have knowledge of this language, they can not even neurologists—will know more about speech, communicate more easily with neurologists. In turn, language, hearing, or swallowing than they will once neurologists may be more willing to learn the language they are through graduate school and their clinical of SLPs and audiologists. An example of this neuro- fellowship. This is not said out of pride, but rather logical language is the word dyskinesia, a general word out of reality; no one has as much clinical training in for a disorder of movement. Neurologists also exten- these areas as a licensed, certified SLP or audiologist, sively use abbreviations (e.g., CVA for cerebral vascu- just like no one has as much knowledge of neurology lar accident, or stroke) and use them considerably in as a neurologist. their charting. Knowing these terms and abbreviations Some readers might be thinking, “Well, that’s all can obviously help the SLP or audiologist understand fine, but I’m not going to work in a hospital or with the neurologist’s assessment report and progress notes. neurologists. I’m going to work in a public school. What Second, knowing about the nervous system and where does all this matter to me?” Manasco (2017) offers a a lesion is (e.g., frontal lobe versus occipital lobe) helps helpful maxim: “When you hear hoof beats, think the SLP anticipate likely patient problems and choose horses, not zebras” (p. 5). What this adage is saying is appropriate initial testing instruments. For exam- that horses are the most likely explanation, while zebras ple, a patient with a focal left hemisphere stroke will are the outliers, the unexpected possibilities. Imagine be tested differently than someone with diffuse brain you are working in a public school and a child walks injury due to a traumatic brain injury. Third, know- into your office. Most likely, the child was sent to your ing about neurological etiologies, such as stroke, trau- office because he or she has a developmental language matic brain injury, and brain tumor, helps an SLP or or speech sound disorder (i.e., a horse). However, it is audiologist predict the kinds of problems patients are possible the child was referred for testing because he likely to face. For example, a patient with occlusion of or she has had a severe concussion or a stroke (i.e., a the middle cerebral artery will have a different symp- zebra). At some point, a child will walk into your office tom complex (e.g., speech and language) than will a and your knowledge of neurology and neurogenic com- patient with posterior cerebral artery occlusion (e.g., munication disorders will be needed to properly assess, visuospatial). Fourth, a working knowledge of neuro- diagnose, and treat that child. As Manasco explains, science helps SLPs and audiologists document patient “You must be able to recognize and treat those prob- change and determine the efficacy of various treatment lems in your field that are very out of the ordinary or methods in rewiring the brain for improved commu- even extraordinary” (2017, p. 5). nication. Fifth and connected to the previous point, knowledge of neural plasticity (i.e., the brain’s ability to change and adapt after injury) helps the SLP plan ther- ▸▸ A Broad Overview of the apy in a way that takes advantage of this phenomenon. One principle of neuroplasticity is that repetition mat- Nervous System ters, meaning repeated experience can help the brain learn new skills. This insight can obviously be used The Nervous System Is a Precious Resource in therapy by giving numerous repetitions of certain I remember watching the 2008 Summer Olympic sounds or words, thus improving a patient’s likelihood Games on television with my 4-­year-old daughters and of learning and generalizing these new skills. seeing their joy and amazement as gymnasts Nastia EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  6 Chapter 1 Introduction to Neurology Liukin and Shawn Johnson moved with grace and pre- cision on the vault, floor exercises, uneven bars, and balance beam (FIGURE 1-­2). Nastia took the gold in the individual all-­around and Shawn the silver. It was a proud moment for the U.S. Olympic squad and all Americans watching these amazingly skilled athletes contort their bodies in incredible ways. The precision, timing, and coordination of these athletes had come from years of training not only their muscles but also their nervous systems. Plans for motor (or movement) activity were developed through years of repetitive action. As the adage goes, “Practice makes perfect.” The nervous system is on full display in the works of our favorite composers and performers. They have FIGURE 1-­3 Itzhak Perlman playing at the White House for fine-­tuned their nervous systems through hours of President George W. Bush and First Lady Laura Bush. practice to execute precisely the actions needed to Courtesy of Shealah Craighead/George W. Bush Presidential Library and Museum. perform a piece of music or create a piece of art. Itzhak Perlman (FIGURE 1-­3), the famous violinist, began What Does Neurology Mean to Me? playing the violin at 3 years old and, although he con- The nervous system is like an automatic transmission tracted polio at an early age, practiced for numerous in a car; one does not need to think about shifting the hours and became one of the world’s most famous vio- gears. The nervous system comes into the forefront linists. Great feats of the body are in part products of when something goes wrong with it. A neurologi- the nervous system. The nervous system is definitely a cal disorder involves a disease in the nervous sys- precious resource, one that works quietly in the back- tem that impairs a person’s health, resulting in some ground, unknown by us unless a disease develops. level of disability. The World Health Organization’s (WHO’s) International Classification of Functioning, Disability and Health (ICF) defines disability as “a universal human experience, sometimes permanent, sometimes transient” that affects the health and functioning of a person (WHO, 2014). We should not think of people in two categories (healthy ver- sus disabled), but rather remember that we are all on a spectrum with health at one end and disability at the other end. There are times in our lives when we experience more health and less disability, and vice versa. Earlier generations used the terms impairment, ­disability, and/or handicap when discussing people who had health issues, and these terms are still widely used in everyday language (e.g., think of how most people refer to parking spaces with a wheelchair sign). WHO has attempted to change this language by using the alternative terms function, activity, and participation. The older terms of impairment, disability, and handicap come from the medical model of disability that puts an emphasis on the person’s health condition, his or her limitations due to this condition, and cures or treat- ment. The medical model does not include the role of society in disability and the barriers a society can erect for those with disabilities (i.e., the social model of dis- FIGURE 1-­2 A gymnast on a balance beam illustrating how ability). The focus of the medical model is on biological years of practice hone the nervous system. and medical answers. WHO’s use of alternative terms is Courtesy of Bill Evans/U.S. Air Force. an attempt to blend the social model of disability, which EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  A Broad Overview of the Nervous System 7 Health condition (disorder or disease) Body functions Participation Activities and structures Environmental Personal factors factors FIGURE 1-­4 The interaction between functioning, disability, and health. Modified from World Health Organization. (2011). World report on disability. Retrieved from http://whqlibdoc.who.int/publications/2011/9789240685215_eng.pdf emphasizes the role of society and its barriers, with the or her interaction with the environment (WHO, 2011). medical model. WHO’s model still has elements of the FIGURE 1-­5 illustrates WHO’s ICF applied to someone medical model by stressing a person’s health condi- who has suffered a spinal cord injury. tion (e.g., stroke) and how that condition has affected It is likely that you have an acquaintance, friend, the structure and function of the body (e.g., paralysis). or family member who suffers from some sort of ner- Issues with function barriers (formerly impairment) vous system problem, such as Alzheimer or Parkinson “are problems in body function or alterations in body disease, which may disable or handicap the person. If structure” (WHO, 2011, p. 5). Examples of function so, then neurology has personal significance to you. issues include paralysis and blindness. In the area of In other words, neurology is not a study that is distant communication disorders, examples include hearing from us; it affects our personal lives, especially when loss and language impairment. Activity barriers (for- our loved ones or we ourselves experience a neurolog- merly disability) “are difficulties in executing activities” ical disorder. (WHO, 2011, p. 5), especially skills of daily living like walking or eating. For example, neurogenic communi- Famous People With Neurological cation disorders can lead to issues in the daily commu- nication of needs and wants with other people or eating. Conditions Lastly, participation barriers (formerly handicap) “are Neurological disorders do not discriminate. They problems with involvement in any area of life” (WHO, strike the old and the young, the rich and the poor, 2011, p. 5). These barriers include challenges participat- and people of every color, culture, and nationality. ing in education and employment, often due to exter- nal barriers such as discrimination and transportation problems. It is important to note that not everyone who Spinal cord injury has a function barrier will have barriers in activity and/ or participation. For example, a person who is deaf may technically have hearing dysfunction but have no issues with daily activities or involvement in other areas of life. Muscular Difficulty Problems in WHO’s ICF also “looks beyond the idea of a purely system below employment moving and waist not and medical or biological conceptualization of dysfunction, working walking transportation taking into account the other critical aspects of disabil- ity” (WHO, 2014), such as environmental and personal factors (FIGURE 1-­4). Environmental factors describe the world in which people with neurological disorders Barrier: some Male: live and interact. These factors can act as either facil- buildings not 25 years itators or barriers and include products, technology, accessible Depressed buildings, support, relationships, attitudes, services, systems, and policies. Personal factors relate directly to FIGURE 1-­5 An example of the ICF applied to a case involving spinal cord injury. the person with a neurological disorder. For example, Adapted from the Centers for Disease Control and Prevention. (n.d.). The ICF: An overview. Retrieved from https://www.cdc.gov a person’s motivation and self-­esteem can play into his /nchs/data/icd/icfoverview_finalforwho10sept.pdf EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  8 Chapter 1 Introduction to Neurology Many famous people have suffered from serious neu- Recurrence rological conditions. Former president Ronald ­Reagan died from complications related to ­Alzheimer ­disease, a progressive neurological disorder that Incidence results in intellectual decline. Actor Michael J. Fox has ­Parkinson disease, a degenerative disorder of the central nervous system characterized by muscle rigid- Prevalence ity and tremors. Actor Christopher Reeve suffered spi- nal cord injury in his upper neck after being thrown from a horse and was wheelchair bound and ventilator dependent until his death in 2004 from cardiac arrest. Mortality Stephen ­Hawking, the famous English physicist, was diagnosed at 21 years of age with an unusual form of FIGURE 1-­6 An illustration of important epidemiological terms. amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig disease); he struggled with this disease until disorders are challenging to obtain due to the rela- his death in 2018 at 76 years old. Roy Horn, an enter- tively few available studies (FIGURE 1-­6 illustrates these tainer from the famous Las Vegas tiger act known important epidemiological terms). One study by Hirtz as Siegfried and Roy, suffered a stroke after his tiger et al. (2007), summarized in FIGURE 1-­7, estimated the Montecore bit him in the neck. Roy had fallen during incidence and prevalence of select neurological disor- a performance, and it is thought that Montecore was ders in the United States. Because population statis- trying to pull him to safety. Most people suffer from tics change rapidly, Hirtz et al.’s information is out of neurological conditions privately, but these celebrities date for some conditions; for example, the Centers for have had to endure their conditions in the public eye. Disease Control and Prevention (2018) and Baio et al. Their willingness to share openly about their condi- (2018) report that the prevalence rate for children with tions has led to greater public awareness regarding autism spectrum disorder is now 16.8/1,000, or 1 in 59 conditions like ALS and Parkinson disease. children. Whatever the statistics, the number of people suf- Prevalence, Incidence, and Cost of fering from neurological disorders is great. In fact, WHO estimates that nearly one in six people world- Neurological Disorders wide, or about 1 billion people, suffer from a neuro- Statistics regarding the incidence (i.e., the num- logical disease (Bertolote, 2007). ber of new cases per year in a given population) and In addition to the personal hardships of people ­prevalence (i.e., the total number of current cases in affected, there is also a tremendous financial cost associ- a given population at a point in time) of neurological ated with the assessment and treatment of neurological A 1400 1275 1200 1000 800 600 400 183 160 200 101 48 4.2 4.5 1.6 0 Epilepsy Multiple Traumatic Spinal ALS Stroke Alzheimer Parkinson A sclerosis brain injury cord injury disease disease FIGURE 1-­7A A. Incidence of select neurological disorders in the United States (new cases per 100,000). EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  A Broad Overview of the Nervous System 9 B 140 121 120 100 80 67 60 40 20 7.1 10 9.5 5.8 3.5 2.4 0.9 0.04 0 Autism Cerebral Tourette Migraine Epilepsy Multiple ALS Stroke Alzhei- Parkin- spectrum palsy syndrome sclerosis mer son B disorders disease disease FIGURE 1-­7B B. Prevalence of select neurological disorders in the United States (total cases per 1,000). ALS = amyotrophic lateral sclerosis. Data from: Hirtz, D., Thurman, D. J., Gwinn-Hardy, K., Mohamed, M., Chaudhuri, A. R., & Zalutsky, R. (2007). How common are the “common” neurologic disorders? Neurology, 68, 332. SCI Parkinson Epilepsy MS 19 15 25 Classification of Neurological Disorders 37 WHO has developed a classification system for diseases, including pathologies of the nervous system, called the International Statistical Classification of Diseases and Related Health Problems. This name is commonly Migraine shortened to the International Classification of Dis- Dementia/AD 78 243 eases and, because it is in its 10th edition, is abbreviated ­ICD-­10. Under “Diseases of the Nervous System,” there are 11 subcategories of neurological diseases (WHO, TBI 2010). These categories are briefly described here: 86 Inflammatory diseases: These are neurological Chronic low diseases caused by bacterial, viral, or parasitic Stroke 110 back pain pathogens. Two conditions under this category 177 are encephalitis (brain infection) and meningitis (infection of membranes that surround the brain and spinal cord). Systematic atrophies primarily affecting the central FIGURE 1-­8 Annual cost of major neurological disorders in billions of dollars. AD = Alzheimer disease, MS = multiple nervous system: Atrophy refers to a wasting away of sclerosis, SCI = spinal cord injury, TBI = traumatic brain injury. something, in this case the nervous system. The pro- Data from: Gooch, C. L., Pracht, E., & Borenstein, A. R. (2017). The burden of neurological disease in the United States: A summary gressive, hereditary disorder known as ­Huntington report and call to action. Annals of Neurology, 81(4), 479–­484. disease is an example of a condition in this category. disorders. Gooch, Pracht, and Borenstein (2017) report Extrapyramidal and movement disorders: The extra- that the following disorders alone cost the United States pyramidal system is that part of the nervous system approximately $800 billion per year: Alzheimer disease that regulates our movements. The basal ganglia and other dementias, stroke, traumatic brain injury, serve as a kind of control center for this system. chronic lower back pain, migraine, epilepsy, multi- Parkinson disease, a degenerative neurological dis- ple sclerosis, spinal cord injury, and Parkinson disease ease involving rhythmic shaking, is an example. (­FIGURE 1-­8). The treatment of Alzheimer disease led the Other degenerative diseases of the nervous system: list with an annual cost of approximately $243 billion. Other conditions that are degenerative in nature, EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  10 Chapter 1 Introduction to Neurology but do not involve the extrapyramidal system, are weakness that occurs, especially to the respiratory included in this category. An example is Alzheimer muscles. disease, which is a progressive neurological disor- Diseases of the myoneural junction and muscle: der involving gradual loss of cognitive abilities. These disorders result from problems where a Demyelinating diseases of the central nervous sys- nerve and muscle connect, called the myoneural tem: Myelin is a white, fatty substance that insu- or neuromuscular junction. Myasthenia gravis is a lates our nerve tracts; thus, demyelinating diseases condition whose name means grave muscle weak- like multiple sclerosis involve the stripping of ness. It is an autoimmune disorder in which the myelin from the nerve tracts. This process leads to body attacks the neuromuscular junction, inhibit- muscle weakness. ing an important chemical needed to make mus- cles contract. Episodic and paroxysmal disorders: This clas- Cerebral palsy and other paralytic conditions: Most sification involves disorders that come and go people have heard of cerebral palsy, which occurs instead of being chronic. They can also be char- due to brain injury before or at birth and leads acterized by sudden or paroxysmal attacks. Epi- to difficulties in muscle tone and posture. These lepsy, headaches, stroke, and sleep disorders problems lead to struggles in completing activities make up the four general conditions found under and interacting with the environment. Spinal cord this category. injury and the resulting weakness or paralysis is Nerve, nerve root, and plexus disorders: These con- included in this category. ditions involve nerves, nerve roots, and branch- Other disorders of the nervous system: WHO has ing networks of nerves. One example is Bell included this category to catch any pathology that palsy, which is a condition that affects the facial does not fit in any of the previous categories. For nerve and causes paralysis to one side of the face. example, episodes of oxygen deprivation, called Another example is phantom limb syndrome, in anoxic events, are classified here. Another exam- which amputees continue to have sensation from ple is hydrocephalus, in which the brain ventri- their absent limb. cles swell and compress the brain tissues against Polyneuropathies and other disorders of the periph- the skull. eral nervous system: The central nervous sys- The ICF, mentioned earlier, is complemen- tem involves the brain and spinal cord, and the tary to the ICD-­10. It lays out a broad framework of peripheral nervous system involves all the nerves health, whereas the ICD-­10 focuses on disease. The that connect the central nervous system with ICF includes the following general categories: body body structures, such as muscles, sense organs, functions, body structures, activities, participation, and glands. Guillain-­Barré syndrome is an acute and environmental factors. There are several subcat- polyneuropathy affecting the peripheral nervous egories that are relevant to the SLP and audiologist; system. It is life threatening due to the profound these are described in BOX 1-­1. Readers can explore BOX 1-­1 International Classification of Functioning, Disability and Health Related to Communication Body Functions Body Structures Chapter 2: Sensory Functions and Pain Chapter 1: Structures of the Nervous System b210–b229 Seeing and related functions s110 Structure of brain b230–b249 Hearing and vestibular functions s120 Spinal cord and related structures Chapter 3: Voice and Speech Functions s130 Structure of meninges b310 Voice functions s140 Structure of sympathetic nervous system b320 Articulation functions s150 Structure of parasympathetic b330 Fluency and rhythm of speech functions nervous system b340 Alternative vocalization functions s198 Structure of the nervous system, b398 Voice and speech functions, other specified other specified b399 Voice and speech functions, unspecified s199 Structure of the nervous system, unspecified EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  A Brief History of Neuroscience 11 Chapter 2: The Eye, Ear, and s330 Structure of pharynx Related Structures s340 Structure of larynx s210 Structure of eye socket s398 Structures involved in voice and speech, s220 Structure of eyeball other specified s230 Structures around eye s399 Structures involved in voice and speech, s240 Structure of external ear unspecified s250 Structure of middle ear s260 Structure of inner ear Activities and Participation s298 Eye, ear, and related structures, Chapter 3: Communication other specified d310–d329 Communicating: receiving s299 Eye, ear, and related structures, d330–d349 Communicating: producing unspecified d350–d369 Conversation and use of Chapter 3: Structures Involved in Voice and Speech communication devices and techniques s310 Structure of nose d398 Communication, other specified s320 Structure of mouth d399 Communication, unspecified Reproduced from: International classification of functioning, Disability and Health (ICF). © World Heath Organization. these subcategories in more detail by visiting the ICF holes, called ­trephines. These were usually sharp ­website (www.who.int/classifications/icf/en/). stones used to create holes in skulls through cut- ting, scraping, and/or drilling. This procedure is known as trephination (FIGURE 1-­10). Why would ▸▸ A Brief History of prehistoric people perform such procedures on each Neuroscience other? There is no written history to rely on, so we have to base our ideas on premodern and modern The history of neuroscience has been a quest to answer the question: How does the brain work? One attempt to answer this question has been that the brain works in bits and pieces, having discrete areas that handle specific functions. The other attempt to answer this question has been that it works more holistically (FIGURE 1-­9). The holistic proponent would say that the brain works as an integrative whole and cannot be broken down into discrete areas. Having said this, there have been people throughout history who thought the brain did not have anything to do with mental functions. We now embark on a brief history of neuroscience. Prehistory Prehistory or prehistoric refers to a period before history was written down, a period prior to about 3500 BCE. What is known about this period comes from various artifacts that have been unearthed. Artifacts that shed light on prehistoric understand- ings of neuroscience include skulls with holes in them and the instruments used in making these Bits and As a How does the brain work? pieces whole FIGURE 1-­10 An example of trephination. FIGURE 1-­9 The spectrum of belief about brain function. Courtesy of the National Library of Medicine. EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  12 Chapter 1 Introduction to Neurology reasons for this procedure. We can guess that pre- historic people performed this procedure to treat headaches, seizures, posttraumatic brain injury, and perhaps even madness or beliefs in evil spir- its. The bottom line is that these people knew there was something special about the head region and they continued to perform trephinations, probably because the procedure worked from time to time. For example, it is conceivable that the procedure successfully relieved pressure in the cranial cavity after a traumatic brain injury, bringing improved functioning to the patient. Early History The Egyptians were cardio-­centrists, meaning they believed the seat of mental functions was in the organ we call the heart. However, they did make observations about damage to the head leading to physical impairments. The Edwin Smith papyrus (3000–2500 BCE) records 48 medical cases, which include cases involving head and brain injury. Here FIGURE 1-­11 Hippocrates. is an example from case 8: Courtesy of the National Library of Medicine. If thou examinest a man having a smash of his skull... thou shouldst palpate his wound. Shouldst thou find that there is a swelling pro- truding on the outside of that smash which is in his skull... on the side of him having that injury which is in his skull; (and) he walks shuffling with his sole, on the side of him having that injury which is in his skull.... (Wilkins, 1964) In this example, the writer is identifying paralysis of one side of the body (i.e., hemiplegia) due to head injury. Like the Egyptians, the Greeks were cardio-­ centrists, but the brain did not go completely unno- ticed. Hippocrates (460–370 BCE) observed that damage to one side of the brain resulted in problems with the opposite side of the body (FIGURE 1-­11). ­Aristotle (384–322 BCE) correctly theorized localiza- tion, the idea that a certain part of the body is respon- sible for certain mental functions, but he attributed these to the wrong organ, the heart instead of the brain (FIGURE 1-­12). What did he believe about the brain? He thought it was a radiator meant to cool the blood, which had been heated up by the heart. Later History Moving into the Common Era (CE), thinkers shifted FIGURE 1-­12 Aristotle. their attention from the heart to the head. Two Courtesy of the National Library of Medicine. EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  A Brief History of Neuroscience 13 famous Romans, Galen (CE 130–200) and Augus- open spaces of the brain known as the v ­ entricles. tine (CE 354–430), postulated that ­mental ­functions This belief gave rise to what is known as the cell were localized in the brain (FIGURE 1-­13). Specifically, ­doctrine, that the cells or ventricles of the brain had they believed these functions were localized in the psychic gases called humors in them responsible for mental functions. This theory persisted for approxi­ mately 1,000 years until the time of the Renaissance, when ­people like Andreas ­Vesalius (1514–1564) began A to conduct careful ­studies of brain anatomy and con- struct detailed drawings, which future scientists would use to more ­thoroughly study the brain (FIGURE 1-­14). Modern History In the 18th and 19th centuries, focus shifted from the brain ventricles to the brain tissue itself. Phrenolo- gists, like Franz Josef Gall (1758–1828), believed that bumps on people’s scalps were due to raised portions of brain tissue (FIGURE 1-­15). These raised portions represented mental strengths, such as memory, math ability, and color perceptions, and personality traits such as agreeableness or combativeness (FIGURE 1-­16). This belief led to the development of the profession of phrenology, whose practitioners examined and ana- lyzed people’s skulls in a procedure called cranioscopy (FIGURE 1-­17). Phrenologists are examples of radical B FIGURE 1-­13 A. Galen. B. Augustine. A. Courtesy of the National Library of Medicine. FIGURE 1-­14 Andreas Vesalius. B. © ilbusca/iStockphoto. Courtesy of the National Library of Medicine. EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  14 Chapter 1 Introduction to Neurology FIGURE 1-­15 Franz Josef Gall performing a cranioscopy. FIGURE 1-­17 Phrenologist performing a cranioscopy. Courtesy of the National Library of Medicine. Courtesy of the National Library of Medicine. FIGURE 1-­18 Marie-­Jean-Pierre Flourens. Courtesy of the National Library of Medicine. localizationists, meaning people who believed certain areas (and only those areas) performed certain mental functions. The opposite view, called holism, was pre- sented by Marie-­Jean-Pierre Flourens (1794–1867), FIGURE 1-­16 Phrenology charts. who asserted that brain function was not so neatly Courtesy of the National Library of Medicine. organized. Flourens (FIGURE 1-­18) argued that the EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  A Brief History of Neuroscience 15 whole brain, not just a discrete part of the brain, was involved in a mental function. particular area was crucial for speech production, and over the course of 2 years he found 12 more cases to In the latter half of the 19th century, a mediating substantiate his original findings. This area is known position between localists and holists known as connec- today as Broca’s area, and the type of language tionism developed. In 1861, Paul Broca (1824–1880) problem associated with damage to it is known as presented a patient nicknamed Tan (because “tan” was Broca’s aphasia. the only word he could say intelligibly) to his peers (­FIGURE 1-­19). Tan demonstrated loss of speech and a right hemiplegia. Tan died shortly after Broca’s presen- tation and his brain was examined, revealing damage to the left frontal portion of the brain known today as Bro- ca’s area (FIGURE 1-­20 and BOX 1-­2). We know from Bro- ca’s work that Broca’s area is a key area in human speech production. Later, Karl Wernicke (1848–1904) built on Broca’s work by identifying an area in the left posterior portion of the brain responsible for understanding lan- guage (­FIGURE 1-­21 and BOX 1-­3). This area eventually was named ­Wernicke’s area. Both Broca and Wernicke contributed to the idea of connectionism, the belief that there are centers in the brain responsible for certain func- tions and that these areas are connected and work coop- eratively (BOX 1-­4). Connectionism of one form or another has domi- nated neuroscience ever since thanks to scientists such as Roman Jakobson (1896–1982), A. R. Luria (1902– 1977), Norman Geschwind (1926–1984), and Harold FIGURE 1-­19 Paul Broca. Courtesy of the National Library of Medicine. BOX 1-­3 Karl Wernicke FIGURE 1-­20 The brain of Leborgne (Tan). Courtesy of the National Library of Medicine. Karl Wernicke was born in Germany in 1848 and studied both neurology and psychiatry. Wernicke, spurred on by Broca’s work in France, began his own BOX 1-­2 Paul Broca investigation on the effects of neuropathologies on speech and language. In his research, he The French physician Paul Broca lived in a time observed that language disturbances occurred of tension in neuroscience. Franz Josef Gall, a when other areas of the brain were damaged, but phrenologist, and Marie-Jean-Pierre Flourens, a holist, Broca’s area was left intact. He found an area on were disputing how the brain worked and where the posterior part of the superior temporal gyrus mental faculties were located. Broca helped to bring that, when damaged, left patients with difficulty the controversy to rest through a patient named understanding other people’s speech and language. Leborgne, more famously known as “Tan” because From this, Wernicke postulated that this area, known this was the only understandable word he said. When today as Wernicke’s area, is crucial for language Tan died, Broca did an autopsy and discovered that comprehension. This area of the brain carries his Tan had a lesion on the third frontal convolution name, as does the form of aphasia associated with of the left hemisphere. Broca concluded that this damage to it: Wernicke’s aphasia. EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  16 Chapter 1 Introduction to Neurology its victims unable to move or speak. Sacks developed a drug treatment that “unfroze” these patients who had not moved in decades. Sacks wrote a book called Awakenings in which he documented his treatment as well as the patients’ temporary recovery. The book was made into a movie of the same name, with Robin Williams playing the role of Sacks. Dr. Sacks published many books of neurological tales, including The Man Who Mistook His Wife for a Hat and An Anthropologist on Mars. Sacks himself suffered from a neurological disorder known as prosopagnosia, or face blindness. Antonio Damasio (b. 1944) is one of the most famous living neurologists (FIGURE 1-­23). He was born in Portugal and studied medicine at the University of Lisbon. He moved to Boston, Massachusetts, and studied under Harold Goodglass at the Aphasia FIGURE 1-­21 Karl Wernicke. Research Center. One of his main research interests has Courtesy of the National Library of Medicine. been the neurobiology of emotions. Two of Damasio’s most famous books are Descartes’ Error: Emotion, Reason and the Human Brain and The Feeling of What Happens: BOX 1-­4 The Duel Body and Emotion in the Making of Consciousness. His wife, Hanna, is also a well-­known neuroscientist. Both It is easy to think that earlier neuroscientists, like Broca of the Damasios currently work at the University of and Wernicke, worked calmly and cooperatively Southern California, and they often publish together. on how the brain works. This was not always the case, however. Joseph Jules Dejerine (1849–1917) is remembered for being one of the first to describe a sudden loss of reading ability, known as alexia. He was a localist in the tradition of Broca and Wernicke. Pierre Marie (1853–1940) was a bitter opponent of Dejerine, accusing Dejerine of poor and substandard work. In response, Dejerine challenged Marie to a duel, thinking his honor had been attacked. The duel never happened. Instead, Marie defused the situation by publishing a letter stating that neither Dejerine’s honor nor work was in question. In 1906, the bold Marie even challenged Broca’s work from 30 years previously, arguing that Tan’s speech loss was due to damage to both Broca’s and Wernicke’s areas, rather than just Broca’s area. Marie’s opinion held sway for over 70 years until 1979, when FIGURE 1-­22 Oliver Sacks. Tan’s brain was scanned using computed tomography technology. The findings supported Broca’s conclusions and showed that Marie was wrong. BOX 1-­5 Where Are the Famous Neurologists of Today? Oliver Sacks (1933–2015) was probably the most famous neurologist in recent memory because of his popular writing (FIGURE 1-­22) FreightBig Pro. He was born in Great Britain but immigrated to the United States in the 1960s. In 1966 he began work at Beth Abraham Hospital, where he treated survivors of encephalitis lethargica, also known as the “sleeping sickness,” which is a disease that became an epidemic in the 1920s. The disease attacks the brain and leaves FIGURE 1-­23 Antonio Damasio. EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  Neuroscience Today 17 Goodglass (1920–2002). Of course, there have contin- ued to be holists holding connectionists responsible BOX 1-­7 The 10% Myth to explain the complexities of brain function. Some of these scientists include John Hughlings Jackson Every year, I quiz my neuroanatomy class about (1835–1911), Pierre Marie (1853–1940), Henry Head what percentage of their brain they think they use. Inevitably, a majority of the class picks “10%.” Where (1861–1940), and Kurt Goldstein (1878–1965). More did this myth come from and how does it stay in the recent neurologists have continued to build upon the public conscience? It probably originated with the work of these scientists (BOX 1-­5). Various theoretical American philosopher William James (1842–1910), perspectives discussed in this section are summarized who believed that humans used only a fraction of their in FIGURE 1-­24. Of course, there is more to the debate mental potential (not brain), which is a plausible idea. than just whether the brain works through inter- He based this idea on cases of incredibly smart people, connected centers or as an integrated whole. BOX 1-­6 like William James Sidis (1898–1944). Named after his discusses another interesting debate called the mind– godfather, William James, Sidis was considered the brain debate and BOX 1-­7 challenges a common myth smartest man who ever lived because of his remarkable about the brain’s functioning. language and mathematical skills. Lowell Thomas, in his 1936 introduction to Dale Carnegie’s How to Win Friends and Influence People, added 10% to James’ statement and said, “Professor William James of Harvard used to Bits and As a say that the average man develops only 10% of his How does the brain work? pieces whole latent mental ability.” In time, “latent mental ability” morphed into “brain” in popular belief, and this myth (Phrenologists) Radical Localists Localists Connectionists Holists has been propagated over time through popular media. One recent example is the 2014 movie Lucy, which tells the story of a woman named Lucy who, as the result of experiments, is able to access 100% of her brain’s potential. Thanks to unlocking the use her FIGURE 1-­24 The range of theoretical perspectives on entire brain, Lucy becomes both omnipresent and the brain. omniscient. The message of the movie is that we only use 10% of our brains leaving 90% unused, and that if we could harness that 90%, we could become Lucy. The truth is that we use 100% of our brains every day. Brain imaging has shown this. In addition, we BOX 1-­6 The Mind–Brain Debate know that damage to a very small part of the brain can lead to catastrophic problems in communication and Look again at the quote that began this chapter by thinking, like in Alzheimer disease and stroke. Lastly, Dr. Stephen Juan: “Every thought, every action, every our brains make up about 2% of our body weight deed relies upon this incredible organ [the brain].” What but consume about 20% of the body’s oxygen. Why does Dr. Juan mean by “every thought... relies”? Is the would only 10% of our brains need this much energy? mind that thinks the same as the brain, or is it different? In The 10% myth is just that: a myth that makes a good other words, can the mind be reduced to brain processes, Hollywood story. or are the mind and the brain different substances that interact with one another? This question is known as the mind–brain debate. When it comes to this question, dualists believe that humans possess two entities, a material brain and an immaterial mind; in contrast, monists believe humans possess one entity only, a material brain/mind. For the majority of history, most ▸▸ Neuroscience Today people held to dualism and believed that humans consist Humans have long desired to see the brain, but early of both a body and a soul and, thus, a brain and a mind. attempts involved opening the cranial vault and With the growing popularity of neuroscience, however, removing the brain. Early investigators, like Broca and this view has been challenged by neuroscientists as well Wernicke, spent years making careful behavioral obser- as some philosophers and theologians who are now vations and then waiting for their subjects to die in opting for monistic explanations for human composition. order to examine their brains. Postmortem dissection is It might appear from this discussion that there are only still the gold standard for some diseases, like Alzheimer two options—dualism or monism—but there are a variety of views under each category (Green & Palmer, disease and chronic traumatic encephalopathy (CTE). 2010; Huffman, 2013). CTE is a condition many former professional football players have suffered that can be reliably diagnosed EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  18 Chapter 1 Introduction to Neurology only postmortem. Generally, however, advances begin- the early 2000s, techniques have been combined and ning in the middle of the 20th century have allowed further refined. researchers to examine subjects while they are still alive. Even with the technological explosion, there are Electrostimulation, or brain mapping, was the still two basic imaging techniques, structural imaging first technique that mapped the responses of the living and functional imaging. Structural imaging shows the brain to specific behaviors. Brain mapping was typ- brain’s anatomy. In contrast, functional imaging shows ically done as patients with conditions such as severe the brain’s activity (i.e., brain physiology)—that is, which epilepsy underwent brain surgery to sever the con- brain areas are active under certain circumstances. There nection between the two cerebral hemispheres. Two is no longer a firm divide between these two types of major observations from brain mapping were made. imaging because structural and functional imaging are First, there is some relationship between a specific area being combined to form new, powerful imaging tools. of the brain and a specific experience or behavior. For example, if a certain part of the primary motor cortex is stimulated, then a body part might move. Similarly, if a Structural Imaging Techniques certain area in the primary sensory cortex is stimulated, The standard in neuroimaging before CT was plain the patient might feel something in a part of the body. x-­ray films (i.e., radiography). This technology was Second, there is a high degree of individual variation used to see dense structures, like bones, but worked in people’s brains. For example, language is localized in poorly for viewing soft tissues like the brain. X-­ray the left hemisphere for most people, but there is a cer- films are still used today to see skull fractures or cra- tain subset of people with language in either the right niofacial abnormalities, but this method needs to be hemisphere or spread between the two hemispheres. used with caution because it involves exposure to radi- The next important event was the development of ation, which can lead to cancer if the patient is overex- the computed tomography (CT) scan in the 1970s. posed to it (Imbesi, 2009). From the 1980s through the present day, there has Computed tomography (tomo is Greek for “a cut- been a technological explosion of neuroimaging tech- ting or section”; graphy is Greek for “a writing”) refined niques. In the 1990s, techniques were refined, and in the use of x-­ray technology (FIGURE 1-­