Introduction to Neurology PDF

© 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 EBSCO Publishing : eBook Collection (EBSCOhost) - printed on 12/16/2020 8:26 AM via PACIFIC UNIV Intr...

© 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 EBSCO Publishing : eBook Collection (EBSCOhost) - printed on 12/16/2020 8:26 AM via PACIFIC UNIV Introduction to Neurology CHAPTER PREVIEW In this chapter we will begin our journey into the world of neuroscience. We will define important terms, like neurology, to help us begin to frame this world. We will then make a case on why it is important for a speech-language pathologist and audiologist to have a working knowledge of the nervous system. Lastly, we will examine theoretical perspectives and technologies that speak to the question: How does the brain work? IN THIS CHAPTER In this chapter, we will... Define the term neurology Discuss why speech-language pathologists and audiologists need to know and understand neurology Discuss why the neurological system is a precious resource Answer the question: What does neurology mean to me? Define the terms function, activity, and participation barriers Survey examples of famous people who have suffered neurological conditions Examine statistics concerning neurological disorders List various categories of neurological disorders Discuss basic theoretical perspectives as to how the brain works Survey important researchers in the history of Copyright 2020. Jones & Bartlett Learning. neuroscience Compare and contrast neuroimaging techniques Discuss why these theoretical perspectives matter to fields associated with communication sciences and disorders AN: 1986080 ; Matthew H Rouse.; Neuroanatomy for Speech-Language Pathology and Audiology Account: s8865459.main.ehost CHAPTER OUTLINE Introduction: Defining Neurology The Need for Neurological Training A Broad Overview of the Nervous System The Nervous System Is a Precious Resource What Does Neurology Mean to Me? Famous People With Neurological Conditions Prevalence, Incidence, and Cost of Neurological Disorders Classification of Neurological Disorders A Brief History of Neuroscience Prehistory  Early History Later History Modern History Neuroscience Today Structural Imaging Techniques Functional Imaging Techniques Combined Structural and Functional Imaging Techniques Which Test When? A Caution Regarding Imaging Techniques Conclusion Summary of Learning Objectives Key Terms Draw It to Know It Questions for Deeper Reflection Case Study Suggested Projects References 3 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. the study of the nervous system’s structure. A neuroana tomical topic is a neuron (i.e., a nervous system ▸ Introduction: Defining cell) and its structure. When we want to talk about how a neuron functions, we have just Neurology entered into the area of neurophysiology. The We begin our journey into the human nervous study of nervous system dis system with this question from the eases is called neuropathology. An example of anthropologist Stephen Juan: “Have you ever neu ropathology would be amyotrophic lateral wondered about how fantastic the human brain sclerosis, or Lou Gehrig disease, which affects really is? Every thought, every action, every both the anatomy and physiology of neurons deed relies upon this incredible organ. Although and leads to serious neurologi cal problems. we take the brain for granted, we couldn’t There are other fields in addition to these, wonder with including neurosurgery (removal of structures out it” (Juan, 1998, p. 1). The brain is the vehicle that impair normal nervous system functioning), we use to wonder. It includes not only the brain neurora diology (use of radiation therapy for but also those other parts of the neurological nervous system tumors), and neuroembryology system that pertain to communication. (normal and patholog ical development of the Neurology is simply the study of the anatomy, nervous system). physiology, and pathology of the nervous sys The nervous system is a series of organs tem. Anatomy is the study of structure, that make communication between the brain physiology is the study of function or structures and body possible in order for us to interact with in motion, and pathology is the study of the world around us. It is through the nervous disease processes that affect both anatomy and system’s connec physiology. Put the prefix neuro- in front of tions to the body (and vice versa) that we think, each of these words and you get distinct yet feel, and act. The most well-known organ of the highly related fields of study. Neuroanatomy is nervous system is the brain, followed by the  spinal cord and the major components of the human nervous then the various nerves (FIGURE 1-1). The system. purpose of this chapter is to give a broad overview of the ner vous system as well as a brief survey of neuroscience’s history and the important figures in that history. This chapter also explores modern neuroimaging tech niques that have led to a better understanding of the brain and how it works. Brain Spinal cord Nerves FIGURE 1-1 The brain, spinal cord, and nerves are EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use system? What difference does this knowledge make to clinical practice? ▸ The Need for Rubens (1977), a neurologist, outlined several rea sons why SLPs and audiologists should Neurological know about neuroscience and neurology. First, he argued that these professionals should know Training how to speak the language of neurology so that they and neurologists could better Why should a speech-language pathologist communicate. Neurologists have their own (SLP) or audiologist be concerned about the language. When communication disorders pro anatomy, physiol ogy pathology of the nervous fessionals have knowledge of this language, autonomous profession als (i.e., they are not they can communicate more easily with supervised by neurologists or other doctors), neurologists. In turn, neurologists may be more they depend on neurologists for many things, willing to learn the language of SLPs and such as referrals and important neurological audiologists. An example of this neuro logical information on the patient (LaPointe, 1977). language is the word dyskinesia, a Tending to their relationships with these general word for a disorder of movement. physicians not only helps SLPs and audiologists Neurologists also exten sively use abbreviations in these areas, but also ultimately helps patients (e.g., CVA for cerebral vascu lar accident, or receive the important and specialized services stroke) and use them considerably in their that only SLPs and audiologists can provide. I charting. Knowing these terms and abbreviations often tell my students that no one— not even can obviously help the SLP or audiologist neurologists—will know more about speech, understand the neurologist’s assessment report language, hearing, or swallowing than they will and progress notes. Second, knowing about the once they are through graduate school and their nervous system and where a lesion is (e.g., clinical fellowship. This is not said out of pride, frontal lobe versus occipital lobe) helps the SLP but rather out of reality; no one has as much anticipate likely patient problems and choose clinical training in these areas as a licensed, appropriate initial testing instruments. For exam certified SLP or audiologist, just like no one has ple, a patient with a focal left hemisphere stroke as much knowledge of neurology as a will be tested differently than someone with neurologist. diffuse brain injury due to a traumatic brain Some readers might be thinking, “Well, that’s injury. Third, know ing about neurological all fine, but I’m not going to work in a hospital or etiologies, such as stroke, trau matic brain injury, with neurologists. I’m going to work in a public and brain tumor, helps an SLP or audiologist school. What does all this matter to me?” predict the kinds of problems patients are likely Manasco (2017) offers a helpful maxim: “When to face. For example, a patient with occlusion of you hear hoof beats, think horses, not zebras” the middle cerebral artery will have a different (p. 5). What this adage is saying is that horses symp tom complex (e.g., speech and language) are the most likely explanation, while zebras are than will a patient with posterior cerebral artery the outliers, the unexpected possibilities. occlusion (e.g., visuospatial). Fourth, a working Imagine you are working in a public school and knowledge of neuro science helps SLPs and a child walks into your office. Most likely, the audiologists document patient change and child was sent to your office because he or she determine the efficacy of various treatment has a developmental language or speech sound methods in rewiring the brain for improved disorder (i.e., a horse). However, it is possible commu nication. Fifth and connected to the the child was referred for testing because he or previous point, knowledge of neural plasticity she has had a severe concussion or a stroke (i.e., the brain’s ability to change and adapt after (i.e., a zebra). At some point, a child will walk injury) helps the SLP plan ther apy in a way that into your office and your knowledge of takes advantage of this phenomenon. One neurology and neurogenic com munication principle of neuroplasticity is that repetition mat disorders will be needed to properly assess, ters, meaning repeated experience can help the diagnose, and treat that child. As Manasco brain learn new skills. This insight can obviously explains, “You must be able to recognize and be used in therapy by giving numerous treat those prob lems in your field that are very repetitions of certain sounds or words, thus out of the ordinary or even extraordinary” (2017, improving a patient’s likelihood of learning and p. 5). generalizing these new skills. A Broad Overview of the Nervous System 5 ▸A Broad Overview SLPs and audiologists must do their part in of the Nervous fos tering good relationships with neurologists and other doctors; one important way of gaining System their col leagues’ respect is by being excellent at what they do. Nothing elicits respect like a job The Nervous System Is a well done. Though SLPs and audiologists are Precious Resource I remember  watching the 2008 Summer Olympic Games on seeing their joy and amazement as gymnasts television with my 4-year-old daughters and 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 fine-tuned their nervous systems through hours of practice to execute precisely the actions needed to perform a piece of music or create a piece of art. Itzhak Perlman (FIGURE 1-3), the famous violinist, began playing the violin at 3 years old and, although he FIGURE 1-2 A gymnast on a balance beam con tracted polio at an early age, practiced for illustrating how years of practice hone the nervous numerous hours and became one of the world’s system. Courtesy of Bill Evans/U.S. Air Force. most famous vio linists. Great feats of the body are in part products of the nervous system. The nervous system is definitely a precious resource, one that works quietly in the back ground, unknown by us unless a disease develops. FIGURE 1-3 Itzhak Perlman playing at the White House for President George W. Bush and First Lady Laura Bush. Courtesy of Shealah Craighead/George W. Bush Presidential Library and Museum. What Does Neurology Mean to Me? The nervous system is like an automatic transmission in a car; one does not need to think about shifting the gears. The nervous  system comes into the forefront when and/or handicap when discussing people something goes wrong with it. A neurologi cal who had health issues, and these terms are still disorder involves a disease in the nervous sys widely used in everyday language (e.g., think of tem that impairs a person’s health, resulting in how most people refer to parking spaces with a some level of disability. The World Health wheelchair sign). WHO has attempted to Organization’s (WHO’s) change this language by using the alternative International terms function, activity, and Classification of participation. The older terms of Functioning, Disability impairment, disability, and and Health (ICF) defines disability as “a handicap come from the medical model universal human experience, sometimes of disability that puts an emphasis on the permanent, sometimes transient” that affects person’s health condition, his or her limitations the health and functioning of a person (WHO, due to this condition, and cures or treat 2014). We should not think of people in two ment. The medical model does not include the categories (healthy ver sus disabled), but rather role of society in disability and the barriers a remember that we are all on a spectrum with society can erect for those with disabilities (i.e., health at one end and disability at the other end. the social model of dis ability). The focus of the There are times in our lives when we medical model is on biological and medical experience more health and less disability, and answers. WHO’s use of alternative terms is an vice versa. attempt to blend the social model of disability, Earlier generations used the terms which impairment, disability, 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) Activities Participation Body functions and structures 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 Personal factors Environmental factors FIGURE 1-4 The interaction between impairment. Activity barriers (for merly disability) “are difficulties in executing activities” (WHO, 2011, p. 5), especially skills of daily living like walking or eating. For example, emphasizes the role of society and its barriers, neurogenic communi cation disorders can lead with the medical model. WHO’s model still has to issues in the daily commu nication of needs elements of the medical model by stressing a and wants with other people or eating. Lastly, person’s health condi tion (e.g., stroke) and how participation barriers (formerly handicap) “are that condition has affected the structure and problems with involvement in any area of life” function of the body (e.g., paralysis). Issues with (WHO, 2011, p. 5). These barriers include function barriers (formerly impairment) “are challenges participat ing in education and problems in body function or alterations in body employment, often due to exter nal barriers such structure” (WHO, 2011, p. 5). Examples of as discrimination and transportation problems. It function issues include paralysis and blindness. is important to note that not everyone who has a In the area of communication disorders, function barrier will have barriers in activity and/ examples include hearing loss and language or participation. For example, a person who is  deaf may technically have hearing dysfunction ical disorder. but have no issues or her interaction with the environment (WHO, Famous People With 2011). FIGURE 1-5 illustrates WHO’s ICF applied to someone who has suffered a spinal Neurological cord injury. Conditions It is likely that you have an acquaintance, Neurological disorders do not discriminate. They friend, or family member who suffers from some strike the old and the young, the rich and the sort of ner vous system problem, such as poor, and people of every color, culture, and Alzheimer or Parkinson disease, which may nationality. disable or handicap the person. If so, then neurology has personal significance to you. In other words, neurology is not a study that is Spinal cord distant from us; it affects our personal lives, injury especially when our loved ones or we ourselves experience a neurolog account the other critical factors can act as either Difficulty aspects of disabil ity” facil itators or barriers moving and walking (WHO, 2014), such as and include products, Problems in employment and with daily activities or transportation involvement in other environmental and technology, areas of life. WHO’s ICF personal factors Muscular system below waist not also “looks beyond the (FIGURE 1-4). working idea of a purely medical Environmental factors Male: or biological describe the world in 25 years conceptualization of which people with Depressed dysfunction, taking into neurological disorders Barrier: some buildings not live and interact. These accessible buildings, support, relationships, attitudes, FIGURE 1-5 An example of the ICF applied to services, systems, and policies. Personal a case involving spinal cord injury. factors relate directly to the person with a Adapted from the Centers for Disease Control and Prevention. (n.d.). The ICF: An overview. Retrieved from https://www.cdc.gov neurological disorder. For example, a person’s /nchs/data/icd/icfoverview_finalforwho10sept.pdf motivation and self-esteem can play into his 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 Roy Horn, an enter tainer from the famous Las Vegas tiger act known as Siegfried and Roy, Many famous people have suffered from serious suffered a stroke after his tiger Montecore bit neu rological conditions. Former president him in the neck. Roy had fallen during a Ronald Reagan died from complications related performance, and it is thought that Montecore to Alzheimer disease, a progressive was trying to pull him to safety. Most people neurological disorder that results in intellectual suffer from neurological conditions privately, but decline. Actor Michael J. Fox has Parkinson these celebrities have had to endure their disease, a degenerative disorder of the central conditions in the public eye. Their willingness to nervous system characterized by muscle rigid ity share openly about their condi tions has led to and tremors. Actor Christopher Reeve suffered greater public awareness regarding conditions spi nal cord injury in his upper neck after being like ALS and Parkinson disease. thrown from a horse and was wheelchair bound and ventilator dependent until his death in 2004 Prevalence, Incidence, from cardiac arrest. Stephen Hawking, the famous English physicist, was diagnosed at and Cost of 21 years of age with an unusual form of Neurological Disorders amyotrophic lateral sclerosis (ALS; also known Statistics regarding the incidence (i.e., the num as Lou Gehrig disease); he struggled with this ber of new cases per year in a given population) disease until his death in 2018 at 76 years old. and prevalence (i.e., the total number of terms). One study by Hirtz et al. (2007), current cases in a given population at a point in summarized in FIGURE 1-7, estimated the time) of neurological incidence and prevalence of select neurological disor ders in the United States. Because population statis tics change rapidly, Hirtz et al.’s Recurrence information is out of date for some conditions; for example, the Centers for Disease Control and Prevention (2018) and Baio et al. (2018) Incidence report that the prevalence rate for children with autism spectrum disorder is now 16.8/1,000, or 1 in 59 children. Prevalence Whatever the statistics, the number of people suf fering from neurological disorders is great. In fact, WHO estimates that nearly one in six people world wide, or about 1 billion people, Mortality suffer from a neuro logical disease (Bertolote, FIGURE 1-6 An illustration of important 2007). epidemiological terms. In addition to the personal hardships of people affected, there is also a tremendous disorders are challenging to obtain due to the financial cost associ ated with the assessment rela tively few available studies (FIGURE 1-6 and treatment of neurological illustrates these important epidemiological 48 101 4.2 4.5 1.6 A 1275 1400 1200 1000 800 600 400 200 0 160 183 A brain injurySpinal Epilepsy Multiple Traumatic ALS Stroke Parkinson disease sclerosis cord injury Alzheimer 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 B 140 120 100 80 60 40 121  System 9 67 20 0 5.8 2.4 3.5 7.10.9 9.5 0.0410 Epilepsy Autism Tourette sclerosis Parkin son spectrum syndrome ALS Stroke Migraine B Cerebral palsyMultiple Alzhei mer 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. WHO has Related Health there are 11 developed a Problems. This subcategories of Epilepsy 37 classification name is commonly neurological system for shortened to the diseases (WHO, diseases, International 2010). These including Classification of categories are Migraine 78 Dementia/AD pathologies of the Dis eases and, briefly described 243 nervous system, because it is in its here: Classificati called the International 10th edition, is abbreviated Inflamma TBI tory 86 on of Statistical ICD-10. Under diseases: MS 25 SCI 19 Neurologica Classification of “Diseases of the These are Parkinson Diseases and Nervous System,” neurological 15 l Disorders bacterial, viral, or parasitic and meningitis (infection of Stroke 110 Chronic low back pain 177 pathogens. Two conditions membranes that surround diseases caused by under this category are the brain and spinal cord). encephalitis (brain infection) system: Atrophy refers to a wasting FIGURE 1-8 Annual cost of major neurological away of something, in this case the nervous disorders in billions of dollars. AD = Alzheimer system. The pro gressive, hereditary disease, MS = multiple sclerosis, SCI = spinal cord disorder known as Huntington disease is an injury, TBI = traumatic brain injury. Data from: Gooch, C. L., Pracht, E., & Borenstein, A. R. (2017). The burden of neurological disease in the United example of a condition in this category. States: A summary report and call to action. Annals of Neurology, 81(4), 479–484. Extrapyramidal and disorders. Gooch, Pracht, and Borenstein (2017) movement disorders: The report that the following disorders alone cost the extra pyramidal system is that part of the United States approximately $800 billion per nervous system that regulates our year: Alzheimer disease and other dementias, movements. The basal ganglia serve as a stroke, traumatic brain injury, chronic lower back kind of control center for this system. pain, migraine, epilepsy, multi Parkinson disease, a degenerative ple sclerosis, spinal cord injury, and Parkinson neurological dis ease involving rhythmic disease (FIGURE 1-8). The treatment of shaking, is an example. Alzheimer disease led the list with an annual Other degenerative cost of approximately $243 billion. diseases of the nervous Systematic atrophies system: Other conditions that are primarily affecting the degenerative in nature, central nervous 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 the profound but do not involve the extrapyramidal system, are included in this category. An weakness that occurs, especially to the example is Alzheimer disease, which is a respiratory muscles. progressive neurological disor der involving Diseases of the gradual loss of cognitive abilities. myoneural junction and muscle: These disorders result from Demyelinating diseases problems where a nerve and muscle of the central nervous connect, called the myoneural or sys tem: Myelin is a white, fatty neuromuscular junction. Myasthenia gravis is substance that insu lates our nerve tracts; a condition whose name means grave thus, demyelinating diseases like multiple muscle weak ness. It is an autoimmune sclerosis involve the stripping of myelin from disorder in which the body attacks the the nerve tracts. This process leads to neuromuscular junction, inhibit ing an muscle weakness. important chemical needed to make mus Episodic and cles contract. paroxysmal disorders: Cerebral palsy and This clas sification involves disorders that other paralytic come and go instead of being chronic. They conditions: Most people have can also be char acterized by sudden or heard of cerebral palsy, which occurs due to paroxysmal attacks. Epi lepsy, headaches, brain injury before or at birth and leads to stroke, and sleep disorders make up the difficulties in muscle tone and posture. four general conditions found under this These problems lead to struggles in category. completing activities and interacting with the Nerve, nerve root, and environment. Spinal cord injury and the plexus disorders: These con resulting weakness or paralysis is included ditions involve nerves, nerve roots, and in this category. branch ing networks of nerves. One example Other disorders of the is Bell palsy, which is a condition that affects nervous system: WHO has the facial nerve and causes paralysis to one included this category to catch any pathology side of the face. Another example is that does not fit in any of the previous phantom limb syndrome, in which amputees categories. For example, episodes of continue to have sensation from their absent oxygen deprivation, called anoxic events, limb. are classified here. Another exam ple is hydrocephalus, in which the brain Polyneuropathies and ventri cles swell and compress the brain other disorders of the tissues against the skull. periph eral nervous system: The central nervous sys tem The ICF, mentioned earlier, is complemen tary to involves the brain and spinal cord, and the the ICD-10. It lays out a broad framework of peripheral nervous system involves all the health, whereas the ICD-10 focuses on disease. nerves that connect the central nervous The ICF includes the following general system with body structures, such as categories: body functions, body structures, muscles, sense organs, and glands. activities, participation, and environmental Guillain-Barré syndrome is an acute factors. There are several subcat egories that polyneuropathy affecting the peripheral are relevant to the SLP and audiologist; these nervous system. It is life threatening due to are described in BOX 1-1. Readers can explore BOX 1-1 International Classification of Functioning, Disability and Health Related to Communication  functions, unspecified Body Functions Body Structures Chapter 2: Sensory Chapter 1: Functions and Pain Structures of the b210–b229 Seeing and related functions Nervous System s110 b230–b249 Hearing and vestibular functions Structure of brain Chapter 3: Voice and s120 Spinal cord and related structures Speech Functions s130 Structure of meninges b310 Voice functions s140 Structure of sympathetic nervous b320 Articulation functions system s150 Structure of parasympathetic b330 Fluency and rhythm of speech nervous system functions b340 Alternative vocalization s198 Structure of the nervous system, functions b398 Voice and speech functions, other specified other specified b399 Voice and speech 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 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 s220 Structure of eyeball speech, other specified s230 Structures around eye s399 Structures involved in voice and s240 Structure of external ear speech, unspecified s250 Structure of middle ear s260 Structure of inner ear Activities and Participation s298 Eye, ear, and related Chapter 3: Communication structures, other specified d310–d329 Communicating: receiving s299 Eye, ear, and related d330–d349 Communicating: producing structures, unspecified d350–d369 Conversation and use of Chapter 3: Structures communication devices and techniques Involved in Voice and d398 Communication, other specified Speech s310 Structure of nose d399 Communication, unspecified s320 Structure of mouth A Brief History of Reproduced from: International classification of functioning, Disability and Health (ICF). © World Heath Organization. The holistic proponent would say that the brain works as an integrative whole and cannot be these subcategories in more detail by visiting the broken down into discrete areas. Having said ICF website this, there have been people throughout history (www.who.int/classifications/icf/en/). who thought the brain did not have anything to do with mental functions. We now embark on a brief history of neuroscience. ▸A Brief History of Prehistory Neuroscience Prehistory or prehistoric refers to a period before The history of neuroscience has been a quest to history was written down, a period prior to about answer the question: How does the brain work? 3500 BCE. What is known about this period One attempt to answer this question has been comes from various artifacts that have been that the brain works in bits and pieces, having unearthed. Artifacts that shed light on discrete areas that handle specific functions. prehistoric understand The other attempt to answer this question has ings of neuroscience include skulls with holes in been that it works more holistically (FIGURE them and the instruments used in making these 1-9).  FIGURE 1-10 An example of trephination. Courtesy of the National Library of Medicine. Bits and pieces How does the brain work? As a whole FIGURE 1-9 The spectrum of belief about brain function. holes, called trephines. These were usually sharp 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 prehistoric people perform such procedures on each other? There is no written history to rely on, so we have to base our ideas on premodern and modern 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 functioning to the patient. reasons for this procedure. We can guess that pre historic people performed this procedure to treat Early History headaches, seizures, posttraumatic brain injury, The Egyptians were cardio-centrists, meaning and perhaps even madness or beliefs in evil spir they believed the seat of mental functions was in its. The bottom line is that these people knew the organ we call the heart. However, they did there was something special about the head make observations about damage to the head region and they continued to perform leading to physical impairments. The Edwin trephinations, probably because the procedure Smith papyrus (3000–2500 BCE) records 48 worked from time to time. For example, it is medical cases, which include cases involving conceivable that the procedure successfully head and brain injury. Here is an example from relieved pressure in the cranial cavity after a case 8: traumatic brain injury, bringing improved  FIGURE 1-11 Hippocrates. 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 FIGURE 1-12 Aristotle. Courtesy of the National Library of Medicine. Moving into the Common Era (CE), thinkers shifted their attention from the heart to the head. Two 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 tine (CE 354–430), postulated that mental open spaces of the brain known as the functions were localized in the brain ventricles. This belief gave rise to what is (FIGURE 1-13). Specifically, they believed known as the cell doctrine, that the cells or these functions were localized in the ventricles of the brain had 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 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 A 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. B. © ilbusca/iStockphoto.  FIGURE 1-14 Andreas Vesalius. 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), who asserted that brain function was not so neatly FIGURE 1-16 Phrenology charts. organized. Flourens (FIGURE 1-18) argued that the 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 BOX 1-3). This area eventually was named Wernicke’s area. Both Broca and Wernicke whole brain, not just a discrete part of the brain, contributed to the idea of connectionism, the was involved in a mental function. belief that there are centers in the brain In the latter half of the 19th century, a responsible for certain func tions and that these mediating position between localists and holists areas are connected and work coop eratively known as connec tionism developed. In 1861, (BOX 1-4). Paul Broca (1824–1880) presented a patient Connectionism of one form or another has domi nicknamed Tan (because “tan” was the only nated neuroscience ever since thanks to word he could say intelligibly) to his peers scientists such as Roman Jakobson (FIGURE 1-19). Tan demonstrated loss of (1896–1982), A. R. Luria (1902– 1977), Norman speech and a right hemiplegia. Tan died shortly Geschwind (1926–1984), and Harold 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  FIGURE 1-20 The brain of Leborgne (Tan). Courtesy of the National Library of Medicine. BOX 1-2 Paul Broca The French physician Paul Broca lived in a time of tension in neuroscience. Franz Josef Gall, a phrenologist, and Marie-Jean-Pierre Flourens, a holist, were disputing how the brain worked and where mental faculties were located. Broca helped to bring the controversy to rest through a patient named Leborgne, more famously known as “Tan” because this was the only understandable word he said. When Tan died, FIGURE 1-19 Paul Broca. Broca did an autopsy and discovered that Tan Courtesy of the National Library of Medicine. had a lesion on the third frontal convolution of the left hemisphere. Broca concluded that this A Brief History of Neuroscience 15 BOX 1-3 Karl Wernicke particular area was crucial for speech production, Karl Wernicke was born in Germany in 1848 and and over the course of 2 years he found 12 more studied both neurology and psychiatry. cases to substantiate his original findings. This Wernicke, spurred on by Broca’s work in area is known today as Broca’s area, and the France, began his own investigation on the type of language problem associated with effects of neuropathologies on speech and damage to it is known as Broca’s aphasia. language. In his research, he observed that language disturbances occurred when other areas of the brain were damaged, but Broca’s area was left intact. He found an area on the posterior part of the superior temporal gyrus that, when damaged, left patients with difficulty understanding other people’s speech and language. From this, Wernicke postulated that this area, known today as Wernicke’s area, is crucial for language comprehension. This area of the brain carries his name, as does the form of aphasia associated with 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  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 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 FIGURE 1-21 Karl Wernicke. Mistook His Wife for a Hat Courtesy of the National Library of Medicine. and An Anthropologist on Mars. Sacks himself suffered from a neurological disorder known as prosopagnosia, or face blindness. BOX 1-4 The Duel Antonio Damasio (b. 1944) is one of the most famous living neurologists (FIGURE 1-23). He It is easy to think that earlier neuroscientists, like was born in Portugal and studied medicine at the Broca and Wernicke, worked calmly and University of Lisbon. He moved to Boston, cooperatively on how the brain works. This was Massachusetts, and studied under Harold not always the case, however. Joseph Jules Goodglass at the Aphasia Research Center. Dejerine (1849–1917) is remembered for being One of his main research interests has been the one of the first to describe a sudden loss of neurobiology of emotions. Two of Damasio’s reading ability, known as alexia. He was a most famous books are Descartes’ localist in the tradition of Broca and Wernicke. Error: Emotion, Reason Pierre Marie (1853–1940) was a bitter opponent and the Human Brain and The of Dejerine, accusing Dejerine of poor and Feeling of What Happens: substandard work. In response, Dejerine Body and Emotion in the challenged Marie to a duel, thinking his honor Making of Consciousness. had been attacked. The duel never happened. His wife, Hanna, is also a well-known Instead, Marie defused the situation by publishing neuroscientist. Both of the Damasios currently a letter stating that neither Dejerine’s honor nor work at the University of Southern California, work was in question. In 1906, the bold Marie and they often publish together. 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 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 FIGURE 1-22 Oliver Sacks. 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  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 pieces How does the brain work? As a whole Goodglass (1920–2002). Of course, there have Every year, I quiz my neuroanatomy class about contin ued to be holists holding connectionists what percentage of their brain they think they use. responsible Inevitably, a majority of the class picks “10%.” Neuroscience Today 17 Where did this myth come from and how does it stay in the public conscience? It probably originated with the American philosopher William BOX 1-7 The 10% Myth James (1842–1910), who believed that humans used only a fraction of their mental potential (not to explain the complexities of brain function. brain), which is a plausible idea. He based this Some of these scientists include John Hughlings idea on cases of incredibly smart people, like Jackson (1835–1911), Pierre Marie William James Sidis (1898–1944). Named after (1853–1940), Henry Head (1861–1940), and his godfather, William James, Sidis was Kurt Goldstein (1878–1965). More recent considered the smartest man who ever lived neurologists have continued to build upon the because of his remarkable language and work of these scientists (BOX 1-5). Various mathematical skills. Lowell Thomas, in his 1936 theoretical perspectives discussed in this section introduction to Dale Carnegie’s How to Win Friends and are summarized in FIGURE 1-24. Of course, Influence People, added 10% to there is more to the debate than just whether the James’ statement and said, “Professor William brain works through inter connected centers or as James of Harvard used to say that the average an integrated whole. BOX 1-6 man develops only 10% of his latent mental discusses another interesting debate called the ability.” In time, “latent mental ability” mind– brain debate and BOX 1-7 challenges a common myth about the brain’s functioning. Bits and (Phrenologists ) Holist s propagated over Lucy, able to access Radical Localist morphed into time through which tells the story 100% of s “brain” in popular popular of a woman named her brain’s Localist s belief, and this media. One recent Lucy who, potential. Thanks to Connectionist example is the as the result of unlocking the use smyth has been 2014 movie experiments, is her FIGURE 1-24 The range of theoretical perspectives on the brain. Look again at the quote that began this chapter by Dr. Stephen Juan: “Every thought, every action, every deed relies upon this incredible organ [the brain].” What does Dr. Juan mean by “every thought... relies”? Is the mind that BOX 1-6 The Mind–Brain Debate thinks the same as the brain, or is it different? In  other words, can the mind be reduced to brain part of the brain can lead to catastrophic processes, or are the mind and the brain problems in communication and thinking, like in different substances that interact with one Alzheimer disease and stroke. Lastly, our brains another? This question is known as the make up about 2% of our body weight but mind–brain debate. When it comes to this consume about 20% of the body’s oxygen. Why question, dualists believe that humans possess would only 10% of our brains need this much two entities, a material brain and an immaterial energy? The 10% myth is just that: a myth that mind; in contrast, monists believe humans makes a good Hollywood story. possess one entity only, a material brain/mind. For the majority of history, most people held to dualism and believed that humans consist of both a body and a soul and, thus, a brain and a mind. With the growing popularity of neuroscience, however, this view has been ▸ Neuroscience Today challenged by neuroscientists as well as some philosophers and theologians who are now Humans have long desired to see the brain, but opting for monistic explanations for human early attempts involved opening the cranial vault composition. It might appear from this discussion and removing the brain. Early investigators, like that there are only two options—dualism or Broca and Wernicke, spent years making monism—but there are a variety of views under careful behavioral obser each category (Green & Palmer, 2010; Huffman, vations and then waiting for their subjects to die 2013). in order to examine their brains. Postmortem entire brain, Lucy becomes both omnipresent and omniscient. The message of the movie is dissection is still the gold standard for some that we only use 10% of our brains leaving diseases, like Alzheimer disease and chronic 90% unused, and that if we could harness that traumatic encephalopathy (CTE). CTE is a 90%, we could become Lucy. condition many former professional football The truth is that we use 100% of our brains players have suffered that can be reliably every day. Brain imaging has shown this. In diagnosed addition, we know that damage to a very small 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 tain subset of people with language in either the right hemisphere or spread between the two only postmortem. Generally, however, advances hemispheres. The next important event was the begin ning in the middle of the 20th century have development of the computed tomography allowed researchers to examine subjects while (CT) scan in the 1970s. From the 1980s through they are still alive. the present day, there has been a technological Electrostimulation, or brain mapping, was the explosion of neuroimaging tech niques. In the first technique that mapped the responses of the 1990s, techniques were refined, and in living brain to specific behaviors. Brain mapping was typ ically done as patients with conditions such as severe epilepsy underwent brain the early 2000s, techniques have been surgery to sever the con nection between the combined and further refined. two cerebral hemispheres. Two major Even with the technological explosion, there observations from brain mapping were made. are still two basic imaging techniques, structural First, there is some relationship between a imaging and functional imaging. Structural specific area of the brain and a specific imaging shows the brain’s anatomy. In experience or behavior. For example, if a contrast, functional imaging shows the brain’s certain part of the primary motor cortex is activity (i.e., brain physiology)—that is, which stimulated, then a body part might move. brain areas are active under certain Similarly, if a certain area in the primary sensory circumstances. There is no longer a firm divide cortex is stimulated, the patient might feel between these two types of imaging because something in a part of the body. Second, there structural and functional imaging are being is a high degree of individual variation in combined to form new, powerful imaging tools. people’s brains. For example, language is localized in the left hemisphere for most people, but there is a cer Structural Imaging Techniques  The standard in neuroimaging before CT was exposure to radi ation, which can lead to cancer plain x-ray films (i.e., radiography). This if the patient is overex posed to it (Imbesi, 2009). technology was used to see dense structures, Computed tomography (tomo is like bones, but worked poorly for viewing soft Greek for “a cut ting or section”; tissues like the brain. X-ray films are still used graphy is Greek for “a writing”) refined the today to see skull fractures or cra use of x-ray technology (FIGURE 1-25). CT niofacial abnormalities, but this method needs to passes be used with caution because it involves around patient CT scanner X-ray detector rotates to remain Direction of opposite the rotation of x-ray source x-ray source X-ray beam Motorized table moves patient into scanner FIGURE 1-25 A patient in a CT scanner. X-ray source generates the beam of x-rays and rotates EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use  white matter lesions. The main way to tell if you are looking at a T1-weighted versus a T2-weighted image is the color Neuroscience Today 19 FIGURE 1-26 Example of a CT scan. Courtesy of Constantin Potagas. x-rays through the human body that reflect off of dif ferent densities of tissue, bone, and fluid in different ways, producing an image (FIGURE 1-26). Structures with higher densities (e.g., bone) show up better than structures with lower densities (e.g., brain tissue). The result is a two-dimensional image, which can be dig itally processed into three-dimensional images. The advantages of this technique are that it is commonly used and thus easily accessible, FIGURE 1-27 Example of an MRI scan. making it a relatively inexpensive procedure. © lucato/iStock/Thinkstock. There are at least four disad vantages to using CT technology. First is the reality that the of the brain ventricles. In the former, the technique uses x-rays, posing a small risk of ventricles will appear black; in the latter, they causing cancer. Second, CT shows anatomy will appear white. The advantages of MRI only and not physiology. Third, the clarity of include a much sharper image (especially of images is an issue when viewing soft tissues of soft tissues) compared to CT. In addition, the body because images are sharpest when of harmful x-rays are not used, thus elim inating the dense structures. Fourth, CTs sometimes do not risk of cancer. Disadvantages include the pick up new damage to soft tissues. A CT taken expense of the test compared to CT, at the time of patient admittance might be claustrophobic reactions due to the narrow tube negative but when repeated the next day might the patient enters, and the presence of be positive for tissue changes. MRI-unsafe metals in the patient’s body (e.g., Magnetic resonance imaging (MRI) uses a cochlear implants, vascular stents, brain magnetic current to flip protons within the body’s aneurysm clips, shrapnel). A sample MRI report water molecules. The signal that is produced is can be viewed in BOX 1-8. picked up by the MRI’s receiver coils and the As mentioned previously, soft tissues are noto data are then formed into three-dimensional riously difficult to see through imaging images (FIGURE 1-27). There are different techniques. Blood vessels, which are made up ways to view tissue using MRI, T1-weighted of soft tissue (endo thelial, connective, and images and T2-weighted images. A T1-weighted smooth muscular tissue) are difficult to image. image is helpful in examining the structure of the However, angiography is an invasive technique cerebral cortex, whereas a T2-weighted image is that uses iodine as a contrast and x-rays to give useful in detecting swelling, inflammation, and excellent pictures of the blood vessels  (FIGURE 1-28). It makes possible the diagnosis diagnose through neuroimaging. The technique of con ditions, like aneurysms and ischemic is invasive, meaning strokes, that previously were very difficult to EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use 20 Chapter 1 Introduction to Neurology BOX 1-8 Sample MRI Report AMERICAN IMAGING CENTER Patient Name: H. R. Date of Birth: 7/11/1927 MRN: 10247583 At the request of: Charles Smith, MD Age: 86 Sex: M Exam Date: 8/8/2013 MRI BRAIN & SELLA W/WO CONTRAST CLINICAL HISTORY: The patient complains of bilateral blurred vision with dizziness and unsteadiness for 2 months. TECHNIQUE: A complete diagnostic set of multiplanar images was acquired using an open-ended, wide-aperture 1.5-Tesla MRI system equipped with high-performance gradients. Turbo parallel processing was employed for enhanced speed. Proprietary sound suppression was provided for patient comfort. Sequence selections, image planes, and slice parameters were adjusted for optimal visualization of regional anatomy and pathology anticipated by the patient’s history. Additional sets of T1-weighted images were obtained following uneventful intravenous injection of 10-cc gradlinium contrast material. FINDINGS: The sella turcica is normal in size and shows a normal-size pituitary gland with uniform enhancement. The carotid siphon segment of both internal carotid arteries shows mild ectasia and tortuosity with a slight medial coursing on the right creating a lateral defect on the pituitary gland. The pituitary stalk is slightly angled to the left as a result. Optic chiasm is normal. There is no upward convexity at the diaphragm sellae nor is there a suprasellar component. There is relatively contiguous increase in signal in periventricular white matter adjacent to the lateral ventricles bilaterally with FLAIR and T2 technique nonenhancing with multiple small foci more peripherally situated in the cerebral hemispheres bilaterally with similar signal characteristics. These are all nonenhancing and represent chronic small vessel ischemic changes. There is no mass lesion demonstrated with no shift in midline structures. The ventricles and cortical sulci are within normal limits for age, and there is no extracerebral fluid collection. There is no evidence of acute or chronic lobar or lacunar infarction. Cranial nerve complex 7 and 8 is normal bilaterally with no evidence of cerebellopontine angle mass lesion. The paranasal sinuses are well aerated without membrane thickening demonstrated. There has been cataract surgery in the right lobe. IMPRESSION: 1. There are relatively severe periventricular white matter changes in both cerebral hemispheres representing chronic small vessel ischemic change. 2. There is mild deformity on the pituitary gland due to impression by slightly tortuous carotid siphon segment of right internal carotid artery without gland enlargement or focal lesion within the gland with normal appearance of optic chiasm. 3. There is no intraparenchymal focal mass or active process demonstrated with no abnormal enhancement noted. Thank you kindly for referring your patient to our office. Gregory G. Stump, MD Board Certified Radiologist there is a risk for bleeding, bruising, clotting, or swell ing at the injection site. It also uses x-rays and thus exposes the patient to radiation (Imbesi, 2009). Functional Imaging Techniques Functional imaging techniques fall into two categories: spatial resolution and temporal resolution. Spatial FIGURE 1-28 A physician observing an angiography. resolution identifies the location of brain activity, EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use whereas temporal resolution techniques deal with the time between a stimulus being introduced and the brain’s response to it. Examples from both of these functional imaging categories will be discussed along with their advantages and disadvantages (TABLE 1-1). Positron emission tomography (PET) is a spatial resolution technology that shows brain activity based on the brain’s glucose metabolism (FIGURE 1-29). The under lying assumption of the technique is that active areas require more energy; thus they consume more glucose. A radioactive isotope, which is chemically attached to a glucose molecule, is injected into a patient’s blood stream. As the isotope decays, it emits photons, which are picked up by the scanner and formed into a three dimensional image. The advantage of this technique is FIGURE 1-29 Example of PET. Courtesy of the Alzheimer’s Disease Education and Referral Center, a service of the National Institute on Aging. TABLE 1-1 Comparison of Spatial Neuroscience Today 21 and Temporal Resolution Techniques Spatial Resolution: Temporal From Resolution: Best to Worst From Best to Worst Functional magnetic EEG resonance imaging (fMRI) Positron emission fMRI tomography (PET) Electroencephalography PET (EEG)  nature of the technique (i.e., it requires an injection into the blood stream) and the fact that a radioactive material is used. Electroencephalography (EEG) is a temporal resolution technique that measures the neuronal elec trical activity through electrodes placed on the scalp (FIGURE 1-30). As a stimulus is presented to a subject’s senses, the EEG monitors the brain’s electrical responses to that stimulus. The result is a graph that compares electrical activity from each electrode over time (FIGURE 1-31). Advantages of this technique include its relatively low cost, the wide availability of the machines, and the good temporal resolution data the technology delivers. Its disadvantages include the limited spatial resolution EEG provides and its limitations in provid ing information on activity in deeper layers of the brain. Combined Structural and Functional Imaging Techniques As we entered the new millennium, many of the FIGURE 1-30 Patient undergoing EEG. techniques described previously have been © Daniela Schraml/ShutterStock, Inc. combined. For example, functional magnetic resonance imag ing (fMRI) combines the that it gives very useful data on brain activity, but advantages of MRI with the there are disadvantages, including the invasive EBSCOhost - printed on 12/16/2020 8:26 AM via PACIFIC UNIV. All use subject to https://www.ebsco.com/terms-of-use 22 Chapter 1 Introduction to Neurology spatial and temporal resolution data in one test.