The Brain Story7 an to publish his observations on the behavior of nag Jackson' of their sei such cha d to be stimulating of the body in the brain:that is,the clonic and tonic jerks in muscles,pro duced by the abnormal epileptic firings of neurons in the brain progressed in the same orderly nattern from one body part to another.This phenomenon led Jackson to b propose a topographic organization in the cerebral cor- th(a)M tex-that is.a map of the body was represented across are-ea-Perre Flo rens (17 860 (b)The a particular cortical area,where one part would repre sent the foot,another the lower leg,and so on.As we will ribed by Flouren this essential feature of brain organization. Without the cerebelum,the animals became uncoordi Although Jackson was iopatia any areas for ab lities such as mem processe were maint of the ter the ain. d to rain par Being an obs field th d tha fo rely.Fo e wh seat in the in te P Phral stroke at: ds.Patients direct their hands vol- one facult.”The the of localized brain aril to ould still ea -ratch the if th That state of affairs didn't last for too long however these observations,he concluded that many regions of New evidence obtained through clinical observations the brain contributed to a given behavior. and autopsies started trickling in from across furone Meanwhile the well-known and respected parisian and it helped to swing the pendulum slowly back to the physician Paul Broca (Figure 1.8a)published,in 1861. localizationist view.In 1836 a neurologist from Montpel- the results of his autopsy on a patient who had been nick- lier,Marc Dax,provided one of the first bits of evidence. named Tan- -perhaps the most famous neurological case He sent a report to the Academy of Sciences about three in history.Tan had developed aphasia:He could under patients,noting that each stand language,but "tan"was the only word he could had speech disturbances utter.Broca found that Tan (his real name was Leborgne) and similar left-hemisphere had a syphilitic lesion in his left hemisphere in the inferior esions found at autopsy.At frontal lobe.This region of the brain has come to be called the time,a report F impact of this fi ling was huge short n Bro a series of such pa icke In 1876.W an net fre uld be ke's n to one He had P egonofheefhg while in England nd whe the ter logist who oral and parietal the neurologist John Hugh. which is now referred to as Wernickes lings Jackson (Figure 1.7) (Figure1.8b)
The Brain Story | 7 began to publish his observations on the behavior of persons with brain damage. A key feature of Jackson’s writings was the incorporation of suggestions for experiments to test his observations. He noticed, for example, that during the start of their seizures, some epileptic patients moved in such characteristic ways that the seizure appeared to be stimulating a set map of the body in the brain; that is, the clonic and tonic jerks in muscles, produced by the abnormal epileptic fi rings of neurons in the brain, progressed in the same orderly patt ern fr om one body part to another. Th is phenomenon led Jackson to propose a topographic organization in the cerebral cortex—that is, a map of the body was represented across a particular cortical area, where one part would represent the foot, another the lower leg, and so on. As we will see , this proposal was verifi ed over a half century later by Wilfr ed Penfi eld. Jackson was one of the fi rst to realize this essential feature of brain organization. Although Jackson was also the fi rst to observe that lesions on the right side of the brain aff ect visuospatial processes more than do lesions on the left side, he did not maintain that specifi c parts of the right side of the brain were solely committ ed to this important human cognitive function. Being an observant clinical neurologist, Jackson noticed that it was rare for a patient to lose a function completely. For example, most people who lost their capacity to speak following a cerebral stroke could still say some words. Patients unable to direct their hands voluntarily to specifi c places on their bodies could still easily scratch those places if they itched. When Jackson made these observations, he concluded that many regions of the brain contributed to a given behavior. Meanwhile, the well-known and respected Parisian physician Paul Broca (Figure 1.8a) published, in 1861, the results of his autopsy on a patient who had bee n nicknamed Tan—perhaps the most famous neurological case in history. Tan had developed aphasia: He could understand language, but “tan” was the only word he could utt er. Broca found that Tan (his real name was Leborgne) had a syphilitic lesion in his left hemisphere in the inferior fr ontal lobe. Th is region of the brain has come to be called Broca’s area . Th e impact of this fi nding was huge. Here was a specifi c aspect of language that was impaired by a specifi c lesion. Soon Broca had a series of such patients. Th is theme was picked up by the German neurologist Carl Wernicke. In 1876, Wernicke reported on a stroke victim who (unlike Broca’s patient) could talk quite fr ee ly but made litt le sense when he spoke. Wernicke’s patient also could not understand spoken or writt en language. He had a lesion in a more posterior region of the left hemisphere, an area in and around where the temporal and parietal lobes mee t, which is now referred to as Wernicke’s area (Figure 1.8b). FIGURE 1.7 John Hughlings Jackson (1835–1911), an English neurologist who was one of the fi rst to recognize the localizationist view. Without the cerebellum, the animals became uncoordinated and lost their equilibrium. He could not, however, fi nd any areas for advanced abilities such as memory or cognition and concluded that these were more diff usely scatt ered throughout the brain. Flourens developed the notion that the whole brain participated in behavior, a view later known as the aggregate fi eld theory . In 1824, Flourens wrote, “All sensations, all perceptions, and all volitions occupy the same seat in these (cerebral) organs. Th e faculty of sensation, percept and volition is then essentially one faculty .” Th e theory of localized brain functions, known as localizationism, fell out of favor. Th at state of aff airs didn’t last for too long, however. New evidence obtained through clinical observations and autopsies started trickling in fr om across Europe, and it helped to swing the pendulum slowly back to the localizationist view. In 1836 a neurologist fr om Montpellier, Marc Dax, provided one of the fi rst bits of evidence. He sent a report to the Academy of Sciences about three patients, noting that each had spee ch disturbances and similar left -hemisphere lesions found at autopsy. At the time, a report fr om the provinces got short shrift in Paris, and it would be another 30 years before anyone took much notice of this observation that spee ch could be disrupted by a lesion to one hemisphere only. Meanwhile, in England, the neurologist John Hughlings Jackson (Figure 1.7) FIGURE 1.6 (a) Marie-Jean-Pierre Flourens (1794–1867), who supported the idea later termed the aggregate fi eld theory. (b) The posture of a pigeon deprived of its cerebral hemispheres, as described by Flourens. a b 002_021_CogNeu_4e_Ch01.indd 7 7/17/13 9:27 AM
8|CHAPTER 1 A Brief History of Cognitive Neuroscience FIGURE 18 (a)Paul Broca(182 L880).(b)The con tions b ke's area conce ned with lanuage。 rehension and meaning Today,differences in h the brainr f the egions.Bec 2003). ag Wernicke's dis ring.(Notetha g this logic german neuroanatomists hes ople had larg ten Willis's ob s in diffo ns.Perhaps the nost famous n Brodm alyzed the cellular prganization of the cortex and char by our predecessors.)With the discoveries of Broca and acterized 52 distinct regions(Figure 1.9).He published Wernicke,attention was again paid to this startling point his cortical mans in 1909 Brodmann used tissue stains Focal brain damage causes specific behavioral deficits. such as the one develoned by franz nissl that perminted As is so often the case,the study of humans leads to him to visualize the different cell types in different brain questions for those who work on animal models.Shortly regions.How cells differ between brain regions is called after broca's discovery.the german physiologists gustay cytoarchitectonics,or cellulararchitecture. Fritsch and Eduard Hitzig electrically stimulated discrete Soon many now-famous anatomists,including Oskar parts of a dog brain and observed that this stimulation Vogt,Vladimir Betz,Theodor Meynert,Constantin von produced characteristic movements in the dog.This dis covery led neuroanatomists to more closely analyze th cerebral corex and its cellular organization;they wante support for their ideas about the importance of loca 3 6 FIGURE 1.10(a)Cami ganglion cells in dog and cat
8 | CHAPTER 1 A Brief History of Cognitive Neuroscience regions. Because these regions performed diff erent functions, it followed that they ought to look diff erent at the cellular level. Following this logic, German neuroanatomists began to analyze the brain by using microscopic methods to view the cell ty pes in diff erent brain regions. Perhaps the most famous of the group was Korbinian Brodmann, who analyzed the cellular organization of the cortex and characterized 52 distinct regions (Figure 1.9). He published his cortical maps in 1909. Brodmann used tissue stains, such as the one developed by Franz Nissl, that permitt ed him to visualize the diff erent cell ty pes in diff erent brain regions. How cells diff er betw ee n brain regions is called cytoarchitectonics , or cellular architecture . Soon many now-famous anatomists, including Oskar Vogt, Vladimir Betz, Th eodor Meynert, Constantin von Today, diff erences in how the brain responds to focal disease are well known (H. Damasio et al., 2004; R. J. Wise, 2003), but a litt le over 100 years ago Broca’s and Wernicke’s discoveries were earth-shatt ering. (Note that people had largely forgott en Willis’s observations that isolated brain damage could aff ect behavior. Th roughout the history of brain science, an unfortunate and oft repeated trend is that we fail to consider crucial observations made by our predecessors.) With the discoveries of Broca and Wernicke, att ention was again paid to this startling point: Focal brain damage causes specifi c behavioral defi cits. As is so oft en the case, the study of humans leads to questions for those who work on animal models. Shortly aft er Broca’s discovery, the German physiologists Gustav Fritsch and Eduard Hitzig electrically stimulated discrete parts of a dog brain and observed that this stimulation produced characteristic movements in the dog. Th is discovery led neuroanatomists to more closely analyze the cerebral cortex and its cellular organization; they wanted support for their ideas about the importance of local FIGURE 1.10 (a) Camillo Golgi (1843–1926), cowinner of the Nobel Prize in 1906. (b) Golgi’s drawings of different types of ganglion cells in dog and cat. a b FIGURE 1.8 (a) Paul Broca (1824–1880). (b) The connections between the speech centers, from Wernicke’s 1876 article on aphasia. A = Wernicke’s sensory speech center; B =Broca’s area for speech; Pc = Wernicke’s area concerned with language comprehension and meaning. a A B Pc b FIGURE 1.9 Sampling of the 52 distinct areas described by Brodmann on the basis of cell structure and arrangement. 9 8 6 4 10 46 11 47 45 44 38 22 21 20 42 41 3 1 2 5 39 40 37 18 19 17 7 43 52 002_021_CogNeu_4e_Ch01.indd 8 7/17/13 9:27 AM
The Brain Story9 conomo,Gerhardt von Bonin andd d.Toalar on of red th ally distinct brain egions.for ex p 18 has proved correct in subsequent functional studies The characterization of the primary visual area of the cortex. area 17 as distinct from surrounding area 18 remark ably demonstrates the power of the cytoarchitectonic approach,as we will consider more fully in Chapter 2. FIGURE112 A bipolar retinal cell illustrating the dendrites and Despite all of this groundbreaking work in cytoarchi axon of the neuron. tectonics,the truly huge revolution in our understanding of the nervous system was taking place elsewhere.in taly and Spain.There,an intense struggle was going on went in only one direction,from the dendrites down to between two brilliant neuroanatomist Oddly,it was the the axonal tip (Figure 1.12). work of one that led to the insights of the other Many gifted scientists were involved in the ear- Golgi (Figure 1.10),an Italian physician,developedon ly history of the neuron doctrine (Shepherd,1991). of the most famous cell stains in the history of the For example,Jan Evangelista Purkinje (Figure 1.13), a Czech,not only described the first nerve cell in the invented the strobo dual ng G 111 to the sue that share ncytoplasm.Ramon y Cajal,who call the father of m s the first to identify the unitary nature of neurons and to articulate what came to be known as the neuron doctrine the concent that the nervous system is made up of individual cells.He also recognized that the transmission of electrical information Cell bod 6 EIGURE 111 (a)San n the system.(b)A Purkinje afferent inflow to the mammallan cortex cell of the cerebellum
The Brain Story | 9 went in only one direction, fr om the dendrites down to the axonal tip (Figure 1.12). Many gift ed scientists were involved in the early history of the neuron doctrine (Shepherd, 1991). For example, Jan Evangelista Purkinje (Figure 1.13), a Czech, not only described the fi rst nerve cell in the nervous system in 1837 but also invented the stroboscope, described common visual phenomena, and made Economo, Gerhardt von Bonin, and Percival Bailey, contributed to this work, and several subdivided the cortex even further than Brodmann had. To a large extent, these investigators discovered that various cytoarchitectonically described brain areas do indee d represent functionally distinct brain regions. For example, Brodmann fi rst distinguished area 17 fr om area 18—a distinction that has proved correct in subsequent functional studies. Th e characterization of the primary visual area of the cortex, area 17, as distinct fr om surrounding area 18, remarkably demonstrates the power of the cytoarchitectonic approach, as we will consider more fully in Chapter 2. Despite all of this groundbreaking work in cytoarchitectonics, the truly huge revolution in our understanding of the nervous system was taking place elsewhere, in Italy and Spain. Th ere, an intense struggle was going on betw ee n tw o brilliant neuroanatomists. Oddly, it was the work of one that led to the insights of the other. Camillo Golgi (Figure 1.10), an Italian physician, developed one of the most famous cell stains in the history of the world: the silver method for staining neurons— la reazione nera , “the black reaction,” that impregnated individual neurons with silver chromate. Th is stain permits visualization of individual neurons in their entirety . Using Golgi’s method, Santiago Ramón y Cajal (Figure 1.11) went on to fi nd that, contrary to the view of Golgi and others, neurons were discrete entities. Golgi had believed that the whole brain was a syncytium , a continuous mass of tissue that shares a common cytoplasm. Ramón y Cajal, who some call the father of modern neuroscience, was the fi rst to identify the unitary nature of neurons and to articulate what came to be known as the neuron doctrine , the concept that the nervous system is made up of individual cells. He also recognized that the transmission of electrical information FIGURE 1.11 (a) Santiago Ramón y Cajal (1852–1934), cowinner of the Nobel Prize in 1906. (b) Ramón y Cajal’s drawing of the afferent infl ow to the mammalian cortex. a b FIGURE 1.12 A bipolar retinal cell, illustrating the dendrites and axon of the neuron. Axon Cell body Dendrites Direction of electrical transmission FIGURE 1.13 (a) Jan Evangelista Purkinje (1787–1869), who described the fi rst nerve cell in the nervous system. (b) A Purkinje cell of the cerebellum. a Dendrites Cell body Axon b 002_021_CogNeu_4e_Ch01.indd 9 7/17/13 9:27 AM
10|CHAPTER 1 A Brief History of Cognitive Neuroscience FIGURE114（a velocity of nerw conduction. maior discoveries.Hermann von Helm Thus,scientists have come to believe that the knowl holtz (Figure 1.14)fig of the rs (the es)n the cell w not a of celluar activity but the with the y whole (i.e. that he the mind) axon of a nerve cell.He was also the first to sugg est that ethe history of research on the mind invertebrates would be good models for studying verte hrate brain mechanisms british nhysiologist sir charles Sherrington vigorously pursued the neuron's behavior as a unit and.ind deed,coined the term synapse to describe The Psychological Story the iunction between two neurons With Golgi,Ramon y Cajal,and these other bright Physicians were the early pioneers studying how the brain worked.In 1869 a Dutch ophthalmologist.Franciscus minds,the neuron doctrine was born-a discovery whose importance was highlighted by the 1906 Nobel Prize in Donders,was the first to propose the now-common Physiology or Medicine shared by Golgi and Ramon method of using differences in reaction times to infer dif y Cajal,and later by the 1932 Nobel Prize awarded to ferences in cognitive processing.He suggested that the Sherrington. difference in the amount of time it took to react to a light As the 20th century progressed,the localization and the amount of time needed to react to a particula st views were color of light was the amount of time required for the erve process of identifying a color.Psychologists began to use e etwo his approach, udy the minc are wh g品 star of experimental psychological sci e the n the prov rote in 1865: cna If it is possible to dissect all the rts of the body,to isolate them in order to study ther in thei out of the enlight riod and held that ture form and connections it is not the same in could he ined th gh the use of re life where all parts coonerate at the same time in a Th common aim.An organ does not live on its own,on could often say it did not exist anatomically.as the and would reject beliefs that,although perhaps com- boundary established is sometimes purely arbitrary What lives,what exists,is the whole,and if one cwmaepic studies all the parts of any mechanisms separately, religion and became the only way to think about the one does not know the way they work. world.In particular,this view,in one form or another
10 | CHAPTER 1 A Brief History of Cognitive Neuroscience a host of other major discoveries. Hermann von Helmholtz (Figure 1.14) fi gured out that electrical current in the cell was not a by-product of cellular activity , but the medium that was actually carrying information along the axon of a nerve cell. He was also the fi rst to suggest that invertebrates would be good models for studying vertebrate brain mechanisms. British physiologist Sir Charles Sherrington vigorously pursued the neuron’s behavior as a unit and, indee d, coined the term synapse to describe the junction betw ee n tw o neurons. With Golgi, Ramón y Cajal, and these other bright minds, the neuron doctrine was born—a discovery whose importance was highlighted by the 1906 Nobel Prize in Physiology or Medicine shared by Golgi and Ramón y Cajal, and later by the 1932 Nobel Prize awarded to Sherrington. As the 20th century progressed, the localizationist views were mediated by those who saw that, even though particular neuronal locations might serve independent functions, the netw ork of these locations and the interaction betw ee n them are what yield the integrated, holistic behavior that humans exhibit. Once again this neglected idea had previously bee n discussed nearly a century earlier by the French biologist Claude Bernard, who wrote in 1865: If it is possible to dissect all the parts of the body, to isolate them in order to study them in their structure, form and connections it is not the same in life, where all parts cooperate at the same time in a common aim. An organ does not live on its own, one could oft en say it did not exist anatomically, as the boundary established is sometimes purely arbitrary. What lives, what exists, is the whole, and if one studies all the parts of any mechanisms separately, one does not know the way they work. Th us, scientists have come to believe that the knowledge of the parts (the neurons and brain structures) must be understood in conjunction with the whole (i.e., what the parts make when they come together: the mind). Next we explore the history of research on the mind. The Psychological Story Physicians were the early pionee rs studying how the brain worked. In 1869 a Dutch ophthalmologist, Franciscus Donders, was the fi rst to propose the now- common method of using diff erences in reaction times to infer differences in cognitive processing. He suggested that the diff erence in the amount of time it took to react to a light and the amount of time nee ded to react to a particular color of light was the amount of time required for the process of identify ing a color. Psychologists began to use this approach, claiming that they could study the mind by measuring behavior, and experimental psychology was born. Before the start of experimental psychological science the mind had bee n the province of philosophers, who wondered about the nature of knowledge and how we come to know things. Th e philosophers had tw o main positions: rationalism and empiricism . Rationalism grew out of the Enlightenment period and held that all knowledge could be gained through the use of reason alone: Truth was intellectual, not sensory. Th rough thinking, then, rationalists would determine true beliefs and would reject beliefs that, although perhaps comforting, were unsupportable and even superstitious. Among intellectuals and scientists, rationalism replaced religion and became the only way to think about the world. In particular, this view, in one form or another, FIGURE 1.14 (a) Hermann Ludwig von Helmholtz (1821–1894). (b) Helmholtz’s apparatus for measuring the velocity of nerve conduction. a b 002_021_CogNeu_4e_Ch01.indd 10 7/17/13 9:27 AM
The Psychological Story11 MILESTONES IN COGNITIVE NEUROSCIENCE Interlude In textbook writing.authors use broad strokes to commu engine in 1807,and Hans Christian Orsted discovered .Iw physicist, studvine electrical currents in tissue.Many vears be personal setting.The social problems that besieged the fore,in 1674,Anton van Leeuwenhoek in Holland had used world's first scientists remain today,in full glory:Issues of a primitive microscope to view animal tissue (Figure 1) that their parents once had the same interests observation was consistent with Rene Descartes's idea and desires as they do,novitiates in science believe they that nerves contained fluid or"spirits,"and these spirits are tackling new iss sues for the first time in human history e responsible for the flow of sensory and motor infor mation in the body (Figure 2).o go further,however.this on the figures we now feature in our brief history orohlems with early microecones not the least of which Shepherd noted how the explosion of research on the was the quality of glass used in the lens.Chromatic aber nervous system started in the 18th century as part of rations made them useless at higher magnification.It was FIGURE 1 (a)Anton van Leeuwenhoek(1632-1723).(b)One of FIGURE 2 Rene Descartes(1596-1650).Portrait by Frans Hals. the original microscopes used by Leeuwenhoek,composed of two orass plates holding the lens was supported by Rene Descartes,Baruch Spinoza,and issues differently,and as a consequence,a rational deci- Gottfried Leibniz. sion is more problematic than a simple logical decision. Although rationalism is frequently equated with logi- Empiricism,on the other hand,is the idea that all cal thinking,the two are not identical.Rationalism con- knowledge comes from sensory experience,that the siders such issues as the meaning of life,whereas logic brain began life as a blank slate.Direct sensory experi- does not.Logic simply relies on inductive reasoning, ence produces simple ideas and concepts.When simple statistics,probabilities,and the like.It does not con- ideas interact and become associated with one another, complex ideas and concepts are created in an individual's knowledge system.The British philosophers-from
The Psychological Story | 11 issues diff erently, and as a consequence, a rational decision is more problematic than a simple logical decision. Empiricism, on the other hand, is the idea that all knowledge comes fr om sensory experience, that the brain began life as a blank slate. Direct sensory experience produces simple ideas and concepts. When simple ideas interact and become as sociated with one another, complex ideas and concepts are created in an individual’s knowledge system. Th e British philosophers—fr om was supported by René Descartes, Baruch Spinoza, and Gott fr ied Leibniz. Although rationalism is fr equently equated with logical thinking, the tw o are not identical. Rationalism considers such issues as the meaning of life, whereas logic does not. Logic simply relies on inductive reasoning, statistics, probabilities, and the like. It does not concern itself with personal mental states like happiness, self- interest, and public good. Each person weighs these In textbook writing, authors use broad strokes to communicate milestones that have become important to people’s thinking over a long period of time. It would be folly, however, not to alert the reader that these scientifi c advances took place in a complex and intriguing cultural, intellectual, and personal setting. The social problems that besieged the world’s fi rst scientists remain today, in full glory: Issues of authorship, ego, funding, and credit are all integral to the fabric of intellectual life. Much as teenagers never imagine that their parents once had the same interests, problems, and desires as they do, novitiates in science believe they are tackling new issues for the fi rst time in human history. Gordon Shepherd (1991), in his riveting account Foundations of the Neuron Doctrine, detailed the variety of forces at work on the fi gures we now feature in our brief history. Shepherd noted how the explosion of research on the nervous system started in the 18th century as part of the intense activity swirling around the birth of modern science. As examples, Robert Fulton invented the steam engine in 1807, and Hans Christian Ørsted discovered electromagnetism. Of more interest to our concerns, Leopoldo Nobili, an Italian physicist, invented a precursor to the galvanometer—a device that laid the foundation for studying electrical currents in living tissue. Many years before, in 1674, Anton van Leeuwenhoek in Holland had used a primitive microscope to view animal tissue (Figure 1). One of his fi rst observations was of a cross section of a cow’s nerve in which he noted “very minute vessels.” This observation was consistent with René Descartes’s idea that nerves contained fl uid or “spirits,” and these spirits were responsible for the fl ow of sensory and motor information in the body (Figure 2). To go further, however, this revolutionary work would have to overcome the technical problems with early microscopes, not the least of which was the quality of glass used in the lens. Chromatic aberrations made them useless at higher magnifi cation. It was not until lens makers solved this problem that microscopic anatomy again took center stage in the history of biology. MILESTONES IN COGNITIVE NEUROSCIENCE Interlude FIGURE 1 (a) Anton van Leeuwenhoek (1632–1723). (b) One of FIGURE 2 René Descartes (1596–1650). Portrait by Frans Hals. the original microscopes used by Leeuwenhoek, composed of two brass plates holding the lens. a b 002_021_CogNeu_4e_Ch01.indd 11 8/1/13 1:25 PM