12 CHAPTERI A Brief History of Cognitive Neuroscience Thomas Hobbes in the followed by a reward would be stamped into the organism ume, s would disappear.Thus,rewards provided a sappear. Thus, me esponse ationism cam avioral psych ologist J hn B. no surpn of that aus's which o ed sh ed.A s believed that the n's e and everybody had the sam e neural cquipment on which of mental develonm ent learning could build.App ealing to the american sense of one ofthe frst scientists tostudy associationism of the re ubuid hrough American hology was giddy with this idea Hermann Ebbinghaus.who.in the late 1800s.decidec that complex processes like memory could be measured learning and experience,and every prominent psychol- and analyzed.He took his lead from the great psycho ogy department in the country was run by people who physicists Gustav Fechner and Ernst Heinrich Weber, held this view. who were hard at work relating the physical properties Behaviorist-associationist psychology went on de- of things such as light and sound to the psychological ex spite the already well-established position- first articu periences that they produce in the observer.These mea- lated by Descartes,Leibniz,Kant,and others-that complexity is built into the human organism.Sensory of he fend hat meb ates psych hely asserted in that golden age,and later ven more the h eshaping of ough Amer psy sed on h n Britai 115.1 were which nition and beh In 1928.Wilder about tho of as Am who had response that ton at Oxford FIGURE116 (a)John B.Watson(1878-1958)(b)Watson and"Little Albert"during one of Watson's fear-conditioning experiments
12 | CHAPTER 1 A Brief History of Cognitive Neuroscience followed by a reward would be stamped into the organism as a habitual response. If no reward followed a response, the response would disappear. Th us, rewards provided a mechanism for establishing a more adaptive response. Associationism came to be dominated by American behavioral psychologist John B. Watson (Figure 1.16), who proposed that psychology could be objective only if it were based on observable behavior. He rejected Ebbinghaus’s methods and declared that all talk of mental processes, which cannot be publicly observed, should be avoided. Associationism became committ ed to an idea widely popularized by Watson that he could turn any baby into anything. Learning was the key, he proclaimed, and everybody had the same neural equipment on which learning could build. Appealing to the American sense of equality , American psychology was giddy with this idea of the brain as a blank slate upon which to build through learning and experience, and every prominent psychology department in the country was run by people who held this view. Behaviorist–associationist psychology went on despite the already well-established position—fi rst articulated by Descartes, Leibniz, Kant, and others—that complexity is built into the human organism. Sensory information is merely data on which pree xisting mental structures act. Th is idea, which dominates psychology today, was blithely asserted in that golden age, and later forgott en or ignored. Although American psychologists were focused on behaviorism, the psychologists in Britain and Canada were not. Montreal became a hot spot for new ideas on how biology shapes cognition and behavior. In 1928, Wilder Penfi eld (Figure 1.17), an American who had studied neuropathology with Sir Charles Sherrington at Oxford, Th omas Hobbes in the 17th century, through John Locke and David Hume, to John Stuart Mill in the 19th century—all emphasized the role of experience. It is no surprise, then, that a major school of experimental psychology arose fr om this associationist view. Psychological associationists believed that the aggregate of a person’s experience determined the course of mental development. One of the fi rst scientists to study associationism was Hermann Ebbinghaus, who, in the late 1800s, decided that complex processes like memory could be measured and analyzed. He took his lead fr om the great psychophysicists Gustav Fechner and Ernst Heinrich Weber, who were hard at work relating the physical properties of things such as light and sound to the psychological experiences that they produce in the observer. Th ese measurements were rigorous and reproducible. Ebbinghaus was one of the fi rst to understand that mental processes that are more internal, such as memory, also could be measured (see Chapter 9). Even more infl uential to the shaping of the associationist view was the classic 1911 monograph Animal Intelligence: An Experimental Study of the Associative Processes in Animals , by Edward Th orndike ( Figure 1.15). In this volume, Th orndike articulated his law of eff ect, which was the fi rst general statement about the nature of associations. Th orndike simply observed that a response that was FIGURE 1.15 Edward L. Thorndike (1874–1949). FIGURE 1.16 (a) John B. Watson (1878–1958). (b) Watson and “Little Albert” during one of Watson’s fear-conditioning experiments. a b 002_021_CogNeu_4e_Ch01.indd 12 7/17/13 9:27 AM
The Psychological Story 13 CANADA Wilder Penfie me that city's first neu In collaboration with When patients began toc Herbert Jasper,he i hich he real proc edure fo oplhinaboutemildmetno、y rons in the brain that produced the seizurcs.To that there are multiple memory svstems.Brenda Mil which cells to destroy,Penfield stimulated various parts of 60w s later is still associated with the montreal neu. the brain with electrical probes and observed the results rological Institute and has seen a world of change sweep on the patients-who were awake,lying on the operating across the study of brain.mind and behavior.She was in table under local anesthesia only.from these observations the vanguard of cognitive neuroscience as well as one of he was able to create maps of the sensory and motor cor the first in a long line of influential women in the field. tices in the brain (Penfield&Jasper,1954)that Hughlings The true end of the dominance of behaviorism and lackson had predicted over half a century earlier. stimulus-response psychology in America did not come until the late 1950s.Psychologistsbeganto think intermso cognition,not just behavior.George Miller (Figure 1.20). Penfield studying the effects of brain surgery and injury who had been a confirmed behaviorist,had a changeo heart in the 1950s.In 1951,Miller wrote an influentia in he preface,' leven years late wept un er the c arpe in a that ctio ast he ide Hebb blished a山arpy ok The Orea of bet de the I N date nd hi cal Theory (Hebb.1949),that cholog ol In it he postulated that mation The held at the Mass hasis The well-known ne (MID.That year had Gre together wire together"is a distillation of hi a rich one for se er sci al that neurons can combine together into a single e.Allen Newell and Herbert Simon successfully in- cessine unit and the connection patterns of these units troduced information processing language l a powerful make up the ever-changing algorithms determining the program that simulated the proof of logic theorems.The brain's response to a stimulus.He pointed out that the computer guru lohn yon neumann wrote the silliman brain is active all the time,not just when stimulated by an lectures on neural organization,in which he considered impulse,and that inputs from the outside can only mod the possibility that the brain's computational activities ify the ongoing activity.Hebb's theory was subsequently were similar to a massively parallel computer.A famous used in the design of artificial neural networks. me ing on artificial intelligence was held at Dartmouth Hebb's British graduate student,Brenda Milner College,where Marvin Minsky,Claude Shannon (known (Figure 1.19),continued the behavioral studies on as the father of information theory),and many others Penfield's patients,both before and after their surgery. were in attendance
The Psychological Story | 13 When patients began to complain about mild memory loss aft er surgery, she became interested in memory and was the fi rst to provide anatomical and physiological proof that there are multiple memory systems. Brenda Milner, 60 years later, is still associated with the Montreal Neurological Institute and has see n a world of change swee p across the study of brain, mind, and behavior. She was in the vanguard of cognitive neuroscience as well as one of the fi rst in a long line of infl uential women in the fi eld. Th e true end of the dominance of behaviorism and stimulus–response psychology in America did not come until the late 1950s. Psychologists began to think in terms of cognition, not just behavior. George Miller ( Figure 1.20), who had bee n a confi rmed behaviorist, had a change of heart in the 1950s. In 1951, Miller wrote an infl uential book entitled Language and Communication and noted in the preface, “Th e bias is behavioristic.” Eleven years later he wrote another book, called Psychology, the Science of Mental Life —a title that signals a complete rejection of the idea that psychology should study only behavior. Upon refl ection, Miller determined that the exact date of his rejection of behaviorism and his cognitive awakening was September 11, 1956, during the second Symposium on Information Th eory, held at the Massachusett s Institute of Technology (MIT). Th at year had bee n a rich one for several disciplines. In computer science, Allen Newell and Herbert Simon successfully introduced Information Processing Language I, a powerful program that simulated the proof of logic theorems. Th e computer guru John von Neumann wrote the Silliman lectures on neural organization, in which he considered the possibility that the brain’s computational activities were similar to a massively parallel computer. A famous mee ting on artifi cial intelligence was held at Dartmouth College, where Marvin Minsky , Claude Shannon (known as the father of information theory), and many others were in att endance. became that city ’s fi rst neurosurgeon. In collaboration with Herbert Jasper, he invented the Montreal procedure for treating epilepsy, in which he surgically destroyed the neurons in the brain that produced the seizures. To determine which cells to destroy, Penfi eld stimulated various parts of the brain with electrical probes and observed the results on the patients—who were awake, lying on the operating table under local anesthesia only. From these observations, he was able to create maps of the sensory and motor cortices in the brain (Penfi eld & Jasper, 1954) that Hughlings Jackson had predicted over half a century earlier. Soon he was joined by a Nova Scotian psychologist, Donald Hebb (Figure 1.18), who spent time working with Penfi eld studying the eff ects of brain surgery and injury on the functioning of the brain. Hebb became convinced that the workings of the brain explained behavior and that the psychology and biology of an organism could not be separated. Although this idea—which kept popping up only to be swept under the carpet again and again over the past few hundred years—is well accepted now, Hebb was a maverick at the time. In 1949 he published a book, Th e Organization of Behavior: A Neuropsychological Th eory (Hebb, 1949), that rocked the psychological world. In it he postulated that learning had a biological basis. Th e well-known neuroscience mantra “cells that fi re together, wire together” is a distillation of his proposal that neurons can combine together into a single processing unit and the connection patt erns of these units make up the ever-changing algorithms determining the brain’s response to a stimulus. He pointed out that the brain is active all the time, not just when stimulated by an impulse, and that inputs fr om the outside can only modify the ongoing activity . Hebb’s theory was subsequently used in the design of artifi cial neural netw orks. Hebb’s British graduate student, Brenda Milner (Figure 1.19), continued the behavioral studies on Penfi eld’s patients, both before and aft er their surgery. FIGURE 1.17 Wilder Penfi eld (1891–1976). FIGURE 1.19 Brenda Milner (1918–). FIGURE 1.18 Donald O. Hebb (1904–1985). FIGURE 1.20 George A. Miller (1920–2012). 002_021_CogNeu_4e_Ch01.indd 13 7/17/13 9:27 AM
14|CHAPTER I A Brief History of Cognitive Neuroscience nose into the worlds of linguistics and computer sci- ima-Rakic In the same 970s (Figure 1.22)put togeth ciplinary team of people King in elect ogy,pl ogy, and abo y ud ot be studied.As oduced the nd how it relates to workin (Goldman-Rakic GURE121 Noam Chomsky -2003 1928-. 1987)I ater she discovered that individual cells in the prefrontal cortex are dedicated to specific memory tasks, such as remembering a face or a voice.She also per- 5g formed the first studies on the influence of dopamine on the prefrontal cortex.Her findings caused a phase shift ique of Defens in the understanding of many mental illnesses-including schizophrenia,which previously had been thought to be by psy the result of bad parenting. pape in which he showed that the of information that can be rehended in a brief p The Instruments of of time atter Neuroscience led Miller to Noam Chomsky's work (Figure 1.21;for a review see Chomsky 2006)where he came acr Changes in electrical impulses,fluctuations in blood perhaps,the most important development to the field flow,and shifts in utilization of oxygen and glucose are Chomsky showed him how the sequential predictability the driving forces of the brain's business.They are alsc of speech follows from adherence to grammatical.not the parameters that are measured and analyzed in the probabilistic,rules.A preliminary version of Chomsky's various methods used to study how mental activities are ideas on syntactic theories,published in September 1956 supported by brain functions.The advances in technol in an article titled,"Three Models for the Description of ogy and the invention of these methods have providec Language, transformed the study of language virtually ts the tools to study how t overnight.The deep message that Miller gleaned vas tha s the mind. the earning theory he in the past 40 yea championed Skin d n this se a brie nd i trans nded all nd all la ation are ed in gre detail in ch 3 ent and th The Electroencephalograph nd the ation In 1875.shortly after Hermann yon Helmholtz figured thods.His ulti ut that it wa actally an electrical impulse w tha goal erstand ho the h along the of an ve,British scien -to understand the workings of the brain tist Richard Canton used a galvanometer to measure con- and the mind many followed his new mission and a few tinuous spontaneous electrical activity from the cerebral years later a new field was born:cognitive neuroscience. cortex and skull surface of live dogs and apes a fancier What has come to be a hallmark of cognitive ncuro version,the "string galvanometer,"designed by a Dutch science is that it is made up of an insalata mista ("mixec physician,Willem Einthoven,was able to make photo- salad")of different disciplines.Miller had stuck his graphic recordings of the electrical activity.Using this
14 | CHAPTER 1 A Brief History of Cognitive Neuroscience nose into the worlds of linguistics and computer science and come out with revelations for psychology and neuroscience. In the same vein, in the 1970s Patricia Goldman-Rakic ( Figure 1.22) put together a multidisciplinary team of people working in biochemistry, anatomy, electrophysiology, pharmacology, and behavior. She was curious about one of Milner’s memory systems, working memory, and chose to ignore the behaviorists’ claim that the prefr ontal cortex’s higher cognitive function could not be studied. As a result, she produced the fi rst description of the circuitry of the prefr ontal cortex and how it relates to working memory ( Goldman-Rakic, 1987). Later she discovered that individual cells in the prefr ontal cortex are dedicated to specifi c memory tasks, such as remembering a face or a voice. She also performed the fi rst studies on the infl uence of dopamine on the prefr ontal cortex. Her fi ndings caused a phase shift in the understanding of many mental illnesses—including schizophrenia, which previously had bee n thought to be the result of bad parenting. The Instruments of Neuroscience Changes in electrical impulses, fl uctuations in blood fl ow, and shift s in utilization of oxygen and glucose are the driving forces of the brain’s business. Th ey are also the parameters that are measured and analyzed in the various methods used to study how mental activities are supported by brain functions. Th e advances in technology and the invention of these methods have provided cognitive neuroscientists the tools to study how the brain enables the mind. Without these instruments, the discoveries made in the past 40 years would not have bee n possible. In this section, we provide a brief history of the people, ideas, and inventions behind some of the noninvasive techniques used in cognitive neuroscience. Many of these methods and their current applications are discussed in greater detail in Chapter 3. The Electroencephalograph In 1875, shortly aft er Hermann von Helmholtz fi gured out that it was actually an electrical impulse wave that carried messages along the axon of a nerve, British scientist Richard Canton used a galvanometer to measure continuous spontaneous electrical activity fr om the cerebral cortex and skull surface of live dogs and apes. A fancier version, the “string galvanometer,” designed by a Dutch physician, Willem Einthoven, was able to make photographic recordings of the electrical activity . Using this Big things were also happening in psychology. Signal detection and computer techniques, developed in World War II to help the U.S. Department of Defense detect submarines, were now being applied by psychologists James Tanner and John Swets to study perception. In 1956, Miller wrote his classic and entertaining paper, “Th e Magical Number Seven, Plus-or-Minus Two,” in which he showed that there is a limit to the amount of information that can be apprehended in a brief period of time. Att empting to reckon this amount of information led Miller to Noam Chomsky ’s work ( Figure 1.21; for a review see Chomsky , 2006), where he came across, perhaps, the most important development to the fi eld. Chomsky showed him how the sequential predictability of spee ch follows fr om adherence to grammatical, not probabilistic, rules. A preliminary version of Chomsky ’s ideas on syntactic theories, published in September 1956 in an article titled, “Th ree Models for the Description of Language, ” transformed the study of language virtually overnight. Th e dee p message that Miller gleaned was that learning theory—that is, associationism, then heavily championed by B. F. Skinner—could in no way explain how language was learned. Th e complexity of language was built into the brain, and it ran on rules and principles that transcended all people and all languages. It was innate and it was universal. Th us, on September 11, 1956, aft er a year of great development and theory shift ing, Miller realized that, although behaviorism had important theories to off er, it could not explain all learning. He then set out to understand the psychological implications of Chomsky ’s theories by using psychological testing methods. His ultimate goal was to understand how the brain works as an integrated whole—to understand the workings of the brain and the mind. Many followed his new mission, and a few years later a new fi eld was born: cognitive neuroscience. What has come to be a hallmark of cognitive neuroscience is that it is made up of an insalata mis ta (“mixed salad”) of diff erent disciplines. Miller had stuck his FIGURE 1.21 Noam Chomsky (1928–). FIGURE 1.22 Patricia Goldman-Rakic (1937–2003). 002_021_CogNeu_4e_Ch01.indd 14 7/17/13 9:27 AM
The Instruments of Neuroscience15 an elect mainecdthcsolketehniqeforno nvasiv a number of years Measuring Blood Flow in the Brain who had skull defects as the result of ne During these studies FIGURE 125 Se flowed around and through their cortex (Figure 1.23) (1915-2000). and noticed that the pulsations of the brain increased the occipital cortex ocally during mental activities such as mathematical calculations.He inferred that blood flow followed func tion.These observations.however.slipped from view and tioned that at the back of his head he heard a noise that were not pursued until a few decades later when in 1928 increased when he used his eyes,but not his other senses. John Fulton presented the case of patient Walter K.,who This noise was a bruit,the sound that blood makes when was evaluated for a vascular malformation that resided it rushes through a narrowing of its channel.Fulton con- above his visual cortex(Figure 1.24).The patient men- cluded that blood flow to the visual cortex varied with the attention paid to surrounding objects. 20 years slipped (Figure cian at the( f you could perf use arter ndently of the b the n and be d be rfusion.With this idea ure the blood flo and metabolisn of the hu e drastic methods in animals their hrain e ther and analzed)kety was able to measure the blood fow to specific regions of the brain (Landau et al.1955).His animal studies provided evidence that blood flow was re. lated directly to brain function.Kery's method and results were used in developing positron emission tomography (described later in this section),which uses radiotracers rather than an inert gas. Computerized Axial Tomography Although blood flow was of interest to those studying brain function,having good anatomical images in order to locate tumors was motivating other developments in instrumentation.Investigators needed to be able to obtain three-dimensional views of the inside of the human body.In the 1930s,Alessandro Vallebona developed FIGURE 1.23 Angelo Mo al setup wa d t measure the pulsa ations of the bran at the site of askull defect
The Instruments of Neuroscience | 15 tioned that at the back of his head he heard a noise that increased when he used his eyes, but not his other senses. Th is noise was a bruit, the sound that blood makes when it rushes through a narrowing of its channel. Fulton concluded that blood fl ow to the visual cortex varied with the att ention paid to surrounding objects. Another 20 years slipped by, and Seymour Kety (Figure 1.25), a young physician at the University of Pennsylvania, realized that if you could perfuse arterial blood with an inert gas, such as nitrous oxide, then the gas would circulate through the brain and be absorbed independently of the brain’s metabolic activity . Its accumulation would be dependent only on physical parameters that could be measured, such as diff usion, solubility , and perfusion. With this idea in mind, he developed a method to measure the blood fl ow and metabolism of the human brain as a whole. Using more drastic methods in animals (they were decapitated; their brains were then removed and analyzed), Kety was able to measure the blood fl ow to specifi c regions of the brain (Landau et al., 1955). His animal studies provided evidence that blood fl ow was related directly to brain function. Kety ’s method and results were used in developing positron emission tomography (described later in this section), which uses radiotracers rather than an inert gas. Computerized Axial Tomography Although blood fl ow was of interest to those studying brain function, having good anatomical images in order to locate tumors was motivating other developments in instrumentation. Investigators nee ded to be able to obtain three -dimensional views of the inside of the human body. In the 1930s, Alessandro Vallebona developed tomographic radiography, a technique in which a series of transverse sections are taken. Improving upon these apparatus, the German psychiatrist Hans Berger published a paper describing recordings of a human brain’s electrical currents in 1929. He named the recording an electroencephalogram. Electroencephalography remained the sole technique for noninvasive brain study for a number of years. Measuring Blood Flow in the Brain Angelo Mosso, a 19th-century Italian physiologist, was interested in blood fl ow in the brain and studied patients who had skull defects as the result of neurosurgery. During these studies, he recorded pulsations as blood fl owed around and through their cortex (Figure 1.23) and noticed that the pulsations of the brain increased locally during mental activities such as mathematical calculations. He inferred that blood fl ow followed function. Th ese observations, however, slipped fr om view and were not pursued until a few decades later when in 1928 John Fulton presented the case of patient Walter K., who was evaluated for a vascular malformation that resided above his visual cortex (Figure 1.24). Th e patient menFIGURE 1.23 Angelo Mosso’s experimental setup was used to measure the pulsations of the brain at the site of a skull defect. FIGURE 1.24 Walter K.’s head with a view of the skull defect over the occipital cortex. FIGURE 1.25 Seymour S. Kety (1915–2000). 002_021_CogNeu_4e_Ch01.indd 15 7/17/13 9:27 AM
16 CHAPTER 1 A Brief History of Cognitive Neuroscience cyclotron)and his colleagues ze that the cy to pro d into biologically a lecules would concentrate in an or FIGURE 1.28 Michael E. heps(1939-】 where the negin to decay The concentra. initial attempts,UCLA neurologist William Oldendorf ion of the tracers could then be measured over time,al- (1961)wrote an article outlining the first description of owing inferences about metabolism to be made. the basic concept later used in computerized tomogra In 1950,Gordon Brownell at Harvard University phy(CT),in which a series of transverse X-rays could be realized that positron decay (of a radioactive tracer reconstructed into a three-dimensional picture.His con was associated with two gamma particles being emit cept was revolutionary,but he could not find any manu ted at 180 degrees.Using this handy discovery,a simple facturers willing to capitalize on his idea.It took insigh positron scanner with a pair of sodium iodide detectors and cash,which was provided by four lads from Liverpool was designed and built,and it was scanning patients for the company EMI,and Godfrey Newbold Hounsfield,a brain tumors in a matter of months(Sweet&Brownell, at the Central Resea 1953).In1959,David E. ent at the olng wit Roy Ed ce high )an Hou dim mm-mitingr r, mage. The radioa d the bill Ho d the firs nd fu tha half crized axial to mography (CAT)sc mn1972 had to hay the and b roll as the d tha Positron Emission Tomography Washington University had both a cyclot and Radioactive Tracers duced radioactive oxygen-15 (O)and rwo researchers Michel ter-Pogossian and William powers who were While CAT was great for revealing anatomical detail,it nterested in using it.They found that when iniected into revealed little about function.Researchers at washingtor the bloodstream.sO-labeled water could be used to mea University,however,used CAT as the basis for developing sure blood flow in the brain (Ter-Pogossian powers positron emission tomography (PET),a noninvasive sec 1958).Ter-Pogossian (Figure 1.27)was joined in the tioning technique that could provide information about 1970s by Michael Phelps (Figure 1.28),a graduate stu- function.Observations and research by a huge number of dent who had started out his career as a Golden Gloves people over many years have been incorporated into what boxer.Excited about X-ray CT,they tho ught that they ould adapt the techn ique to reconstruct the ctive isotopes,a racers n an rgan cal"radion employs. y not ne wor e e They de 10 po ograp PEI (Figure 1975, PET n after be led E wrence (the and Al
16 | CHAPTER 1 A Brief History of Cognitive Neuroscience cyclotron) and his colleagues at the University of California, Berkeley to realize that the cyclotron could be used to produce radioactive substances. If radioactive forms of oxygen, nitrogen, or carbon could be produced, then they could be injected into the blood circulation and would become incorporated into biologically active molecules. Th ese molecules would concentrate in an organ, where the radioactivity would begin to decay. Th e concentration of the tracers could then be measured over time, allowing inferences about metabolism to be made. In 1950, Gordon Brownell at Harvard University realized that positron decay (of a radioactive tracer) was associated with tw o gamma particles being emitted at 180 degree s. Using this handy discovery, a simple positron scanner with a pair of sodium iodide detectors was designed and built, and it was scanning patients for brain tumors in a matt er of months (Swee t & Brownell, 1953). In 1959, David E. Kuhl, a radiology resident at the University of Pennsylvania, who had bee n dabbling with radiation since high school (did his parents know?), and Roy Edwards, an enginee r, combined tomography with gamma-emitt ing radioisotopes and obtained the fi rst emission tomographic image. Th e problem with most radioactive isotopes of nitrogen, oxygen, carbon, and fl uorine is that their halflives are measured in minutes. Anyone who was going to use them had to have their own cyclotron and be ready to roll as the isotopes were created. It happened that Washington University had both a cyclotron that produced radioactive oxygen-15 ( 15 O) and tw o researchers, Michel Ter-Pogossian and William Powers, who were interested in using it. Th ey found that when injected into the bloodstream, 15 O-labeled water could be used to measure blood fl ow in the brain (Ter- Pogossian & Powers, 1958). Ter-Pogossian (Figure 1.27) was joined in the 1970s by Michael Phelps (Figure 1.28), a graduate student who had started out his caree r as a Golden Gloves boxer. Excited about X-ray CT, they thought that they could adapt the technique to reconstruct the distribution within an organ of a short-lived “physiological” radionuclide fr om its emissions. Th ey designed and constructed the fi rst positron emission tomograph, dubbed PETT (positron emission transaxial tomography; Ter-Pogossian et al., 1975), which later was shortened to PET. Another metabolically important molecule in the brain is glucose. Under the direction of Joanna Fowler and Al initial att empts, UCLA neurologist William Oldendorf (1961) wrote an article outlining the fi rst description of the basic concept later used in computerized tomography (CT), in which a series of transverse X-rays could be reconstructed into a three -dimensional picture. His concept was revolutionary, but he could not fi nd any manufacturers willing to capitalize on his idea. It took insight and cash, which was provided by four lads fr om Liverpool, the company EMI, and Godfr ey Newbold Hounsfi eld, a computer enginee r who worked at the Central Research Laboratories of EMI, Ltd. EMI was an electronics fi rm that also owned Capitol Records and the Beatles’ recording contract. Hounsfi eld, using mathematical techniques and multiple tw o-dimensional X-rays to reconstruct a three -dimensional image, developed his fi rst scanner, and as the story goes, EMI, fl ush with cash fr om the Beatles’ success, footed the bill. Hounsfi eld performed the fi rst computerized axial tomography (CAT) scan in 1972. Positron Emission Tomography and Radioactive Tracers While CAT was great for revealing anatomical detail, it revealed litt le about function. Researchers at Washington University , however, used CAT as the basis for developing positron emission tomography (PET), a noninvasive sectioning technique that could provide information about function. Observations and research by a huge number of people over many years have bee n incorporated into what ultimately is today’s PET. Its development is interwoven with that of the radioactive isotopes, aka “tracers,” that it employs. We previously noted the work of Seymour Kety done in the 1940s and 1950s. A few years earlier, in 1934, Irene Joliot-Curie ( Figure 1.26) and Frederic Joliot-Curie discovered that some originally nonradioactive nuclides emitt ed penetrating radiation aft er being irradiated. Th is observation led Ernest O. Lawrence (the inventor of the FIGURE 1.26 Irene Joliot-Curie (1897–1956). FIGURE 1.27 Michel M. Ter-Pogossian (1925–1996). FIGURE 1.28 Michael E. Phelps (1939–). 002_021_CogNeu_4e_Ch01.indd 16 7/17/13 9:27 AM