Departments of Neurosurgery (SU, RPL), Neurology (RPL, BG), and Psychology (RPL, BG), School of Medicine, and The Zanvyl Krieger Mind/Brain Institute (RPL, BG), The Johns Hopkins University, Baltimore, Maryland Neurosurgery 30; 904-913, 1992 ABSTRACT: According to Penfield, the work of Charles Sherrington's laboratory forced a change from the long-held concept of a broad, overlapping sensorimotor cortex to the concept of a narrow, discrete pre-Rolandic motor cortex separate from the post-Rolandic sensory strip. Harvey Cushing, one of the founders of modern neurosurgery, coined the term narrow motor strip. Cushing also appears to have been the first to color the precentral gyrus in a mosaic pattern and to use red coloring for the motor cortex and blue for the sensory cortex. Cushing's red and blue color coding is still used in textbooks, nearly 100 years later. In this article, we review the historical evolution of and the evidence for the concept of narrow and discrete motor and sensory strips anterior and posterior to the Rolandic cortex. A review of the historical development of the concept and recent physiological studies reaffirms the proposition that the motor and sensory areas are much broader and more complex than they were thought to be in the classic teaching that originated with Sherrington and Cushing. KEY WORDS: Harvey Cushing; History of medicine; Victor Horsley; Sensorimotor cortex; Charles Sherrington BIRTH OF CEREBRAL LOCALIZATION As early as the fifth century B.C., the ancient Greek physician, Hippocrates, appreciated the laterality of motor function: He noted that unilateral brain injury is followed by paralysis of the opposite side of the body (1,64). Nevertheless, for the 23 centuries after Hippocrates, no scientific theories were advanced to explain these associations. Instead, interest in cerebral physiology centered on philosophical discussions of the seat of the soul. The brain was thought to act as a whole, with no localization of its functions. The global conception of brain function began to shift toward a more localized, segmental conception in the first part of the nineteenth century when Frank Joseph Gall provided a different view. He observed that a patient with a fencing foil wound in the frontal lobe of the brain had a speech disturbance. He theorized that the frontal portion of the brain contained the faculty of memory and

JACKSON AND FERRIER TO HORSLEY--A BROADER SENSORIMOTOR CONCEPT Declaration of cerebral localization in the modern sense came in John Hughlings Jackson's (34) statement that "The convolutions of the brain must contain nervous arrangements representing movements. There is nothing else they can represent except movements and impressions." In 1861, Pierre Paul Broca (7), the prominent French surgeon, reported that a localized small area in the third convolution of the left frontal lobe of man was responsible for speech. He based his report on observations of a patient who died after a left hemispheric brain lesion. John Hughlings Jackson (1864) supported Broca's observation (34). Jackson's contemporaries, Fritsch and Hitzig (1870), have been given credit for the first experimentally controlled direct electrical stimulation of mammalian cerebral cortex. When they applied galvanic current through bipolar electrodes to the anterior half of the canine cerebral hemisphere, they obtained movement of muscle groups in the opposite half of the body. They could not elicit movement by stimulation of the posterior hemisphere (20,21). Direct electrical stimulation of human brain to produce sensory or motor responses was first performed in 1874 (2,62). An American woman in Cincinnati, Ohio, granted her surgeon, Roberts Bartholow, permission to insert wires through the granulation tissue overlying the crater of an abscess in the left cerebral convexity. As current was applied, the surgeon observed contractions of musculature in the contralateral arm and leg. In 1876, when Ferrier (18) reported movement in response to stimulation of points behind the Rolandic fissure in several species, including the monkey, Hitzig (30) criticized these results. He believed that the areas behind the Rolandic fissure were sensory centers. Nevertheless, Ferrier (18) made a map of the human brain by transferring a map of his stimulation of the monkey cortex to an outline of the human brain. Ferrier's brain map shows the motor area extending in front of and behind the Rolandic fissure (Fig. 1). His map was used for many decades thereafter as a teaching and working diagram (37). In 1878, Luciani and Tamburini (43) conducted cortical removal experiments, and their conclusions opposed the concept of two separate cortical areas for motor and sensory responses. They introduced the concept of the combined sensorimotor area. In 1887, Victor Horsley (31), surgeon to the National Hospital for the Paralysed and Epileptic (Queen Square, London), published his maps of the human brain, based on his own experiments on monkeys and to some extent on observations in humans. His maps showed an area of motor representation similar to that in Ferrier's map. The motor area extended both in front of and behind the Rolandic fissure and was rather broad (Fig. 2). In the same year, William W. Keen became the new editor

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AUTHOR(S): Uematsu, Sumio, M.D.; Lesser, Ronald P., M.D.; Gordon, Barry, M.D., Ph.D.

speech. Because Gall was closely linked with the pseudoscience of phrenology, however, his theory was not accepted by scientists of his day (58). Downloaded from https://academic.oup.com/neurosurgery/article-abstract/30/6/904/2751858 by Library Serials Dept UT Southwestern Medical Center user on 12 October 2018

Neurosurgery 1992-98 June 1992, Volume 30, Number 6 904 Localization of Sensorimotor Cortex: The Influence of Sherrington and Cushing on the Modern Concept Historical Article

SHERRINGTON'S ATTEMPT TO DELIMIT THE MOTOR CORTEX A series of physiological studies by Charles S. Sherrington (Table 1) (27,40,56) and anatomical structural studies of the Rolandic cortex in the early 1900s opened a new era of cerebral localization. According to Cushing, Sherrington's physiological studies attempted to delimit the motor and sensory cortex (15). Sherrington used a monopolar electrode instead of the bipolar electrode employed by his predecessors. Aside from his attempt to delimit the motor cortex by electrical stimulation on anthropoids, he was actively helping young Alfred Campbell, an Australian graduate, with his histological work on the motor and sensory cortex (5,8,9,17). Campbell was a frequent visitor to Sherrington's Liverpool laboratory to observe the electrical stimulation studies performed by Gruenbaum and Sherrington. According to John C. Eccles (17), from 1900 to 1903, Campbell examined 25 brain specimens from higher apes. The specimens were turned over to him by Sherrington after completion of stimulation studies. Campbell used three specimens for detailed cytoarchitectural studies: two chimpanzee and one orangutan brain (9,17). The final cytoarchitectural studies were presented to the Royal Society of London by Sherrington in November 1903. Campbell was able to publish the work in book form with the aid of a grant from the Royal Society in 1906 (9). Campbell's publication undoubtedly further directed Sherrington's thoughts and probably influenced subsequent research on cerebral mapping toward separating the pre-Rolandic area for motor cortex from the post-Rolandic for sensory. Campbell stated that there were no motor cells (Betz cells) in the cortex behind the Rolandic fissure, but, instead, the area was rich with small granular cells. Furthermore, he believed that the arrangement of the post-Rolandic fibers was more indicative of a sensory center (9,31). SHERRINGTON AND CUSHING (CUSHING'S VISIT TO SHERRINGTON'S LABORATORY) Harvey Cushing, an emerging "brain surgeon" of that time, was probably influenced by exposure to Sherrington's and Campbell's work at an early stage of his career. In the summer of 1901, Cushing had just completed 5 years of surgical training under Halsted in Baltimore. He then traveled to Europe, visiting several clinics and laboratories. During the latter part of his journey, he spent about a month at Sherrington's laboratory in Liverpool, England, where Sherrington was working with anthropoid primates (23) . He helped Sherrington open the primate's skull, and he also made drawings of parts of the anthropoid brain that Sherrington later used when he and Gruenbaum (his name changed to Leyton later)

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performed experiments on 12 monkeys, using a controlled method (31). Munk theorized that the Rolandic area had a mechanism for storing up the memories of movements. He declared that no part of the cortex should be termed the pure motor area (31). In 1903, Keen drew his own map of the human brain as well for An American Textbook of Surgery (38).

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of Gray's Anatomy, and he added a section entitled "Cerebral Localization and Topography" for the first time in the book's history (36). This section used the brain maps of both Ferrier and Horsley. Keen stated that these maps served as "working diagrams." The year of 1888 was probably the most exciting year for American brain surgeons. It included a visit by Victor Horsley as an invited guest to Washington, D.C., to deliver a lecture on the sensorimotor cortex at the Congress of American Physicians and Surgeons (32) . At that time, American surgeons in the Philadelphia area were busy with brain stimulation studies. They performed cortical stimulation studies on their patients with focal epilepsy. They observed the excitability of motor cortex from electrical stimulation. For example, on May 30, 1888, W.W. Keen, Professor of Surgery in the Women's Medical College of Pennsylvania, using his "double brain electrode" (Fig. 3), excised cerebral cortex governing the left wrist and hand from a patient with focal seizures in the left wrist and hand after the area had been determined by electrical stimulation. His findings were read before the American Surgical Association on September 18, 1888 (37). On June 12, 1888, J.B. Deaver, another surgeon in Philadelphia, excised the cortical area representing the hand, as demonstrated by electrical stimulation. The electrical stimulation was performed by J.H. Lloyd and was attended by many other physicians, including C.K. Mills. In September of that year, the findings were read before the Congress of American Physicians and Surgeons in Washington, D.C. by Lloyd (42). Finally, on October 4, 1888, in the "private operating room" of the Jefferson Medical College Hospital in Philadelphia, C.B. Nancrede (51) exposed the Rolandic area of the brain in a patient with focal epilepsy. A battery-operated probe applied to this area caused twitching of the patient's thumb, and, using the same procedure, the surgical team mapped the patient's brain areas for motor control of shoulder, elbow, forearm, and face. These areas were found to be located as delineated in Horsley's map. The surgery was attended by 12 physicians and "many undergraduates." Their experience was presented before the Philadelphia Academy of Surgery on November 6, 1888. In the same year, Mills of Philadelphia read his 173-page article, "Cerebral Localization in Its Practical Relations," before the Congress of American Physicians and Surgeons in Washington D.C. (the same congress that Victor Horsley was attending). Mills' presentation was printed in Brain--The Journal of Neurology in 1890 (47) . His map showed general agreement with Horsley's map (Fig. 4) (31). The face, finger, wrist, elbow, shoulder, hip, knee, foot, and toe motor areas extended in front of and behind the Rolandic fissure (47) . According to Penfield, Nancrede (51) as well as Lloyd and Deaver (42) made their own human brain maps that basically resembled the work of Horsley (31) . In 1890, Munk (50) in Germany showed that electrical stimulation of the gyrus posterior to the Rolandic fissure resulted in motor responses. He

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human brain (Fig. 6). The drawing showed the Rolandic fissure as an undisputed dividing line, with motor cortex in front of it and sensory area behind it. The drawing was made for the chapter "Surgery of the Head" in W.W. Keen's surgery text (13,23,24). Cushing was congratulated on the chapter by letters from W.W. Keen on November 24, 1907, from Halsted on April 25, 1908, and from Horsley on May 1, 1908 (23) . It should be noted, however, that this map was drawn before Cushing's sensory stimulation study on two conscious patients (14). Cushing's sensory stimulation study on the awake patients took place on July 6, 1908 (his first patient), and December 8, 1908 (the second patient). The first patient suffered from convulsive attacks originating in his right hand and the right side of his face. The second patient was similar to the first, with attacks beginning in his right hand. His motor seizures were frequently inaugurated by a stinging sensation "like an electric shock" between the little and ring fingers. Both patients underwent two-stage surgery. The first stage was to open the skull (osteoplastic craniotomy) and was performed with the patient under morphia and chloroform general anesthesia. The second stage took place 20 days later in the first patient and 6 days later in the second patient. The second-stage surgery was begun under morphia and chloroform anesthesia, but the anesthetic inhalation was terminated as "the original bone-flap was quickly re-elevated." Cortical stimulation was performed using a unipolar electrode. A broad plate of the other pole (indifferent electrode plate) was applied to the ipsilateral thigh. Faradic current of one-half the strength that had been needed "to elicit distinct movements from the cortex of a recent case under anesthesia" was used. The electrode tip was a coiled platinum wire ("Sherrington pattern"). The electrode tip was lightly touched to the cortex for the "briefest moment of time" (14). The second patient, who had been informed of the experimental objective, "was eager to assist in every way in his power. . . and responded, saying that he experienced a sensation which he located in the index finger of the right hand." Upon stimulation of the gyrus lying "anterior to the large vein. . . a prompt flexion of the thumb into the palm of the hand followed." Cushing stated, "This observation was sufficient to certify the position of the fissura centralis . . . (Rolandic)" (Fig. 7). Cushing summarized his observations on the two patients in Brain--The Journal of Neurology in 1909. His conclusion was that stimulation of the postcentral convolution elicited a definite sensory response. The location of the central fissure was determined by obtaining characteristic motor responses from the precentral area (14). According to Penfield, this was the first detailed sensory stimulation study on human brain while the patient was awake to report sensory representation (14,54). Cushing's map showed all motor responses in front of and sensory responses behind the Rolandic fissure, and it depicted the sensations in particular body parts as corresponding to movement in the same body parts. Thus, the physiological work of Sherrington, the cytoarchitectural study of Campbell, and Cushing's

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reported their results (Fig. 5) (27,40). Cushing described his impressions of Sherrington's laboratory in a letter to his father and in his diary. His initial impression of Sherrington's laboratory work was of disappointment. In some of his records, he questioned the credibility of Sherrington's cortical localization experiments. Cushing noted that Sherrington was a young, almost boyish, man of 36 (actually he was 43), nearsighted, wearing (when he had not lost them) a pair of gold spectacles. He continued that, in spite of Sherrington's own claim that he had a bad memory, the senior scientist took only a few notes during experiments (23,26). Cushing was dismayed to observe that the cortical area excited by electrical stimulation was only the crest of the convolution over the upper part of the ascending parietal convolution. Cushing wondered about the excitability of the deeper-seated convolutions folded away from the cortical surface. In an attempt to address this problem, Sherrington drained the subarachnoid fluid and sliced away some of the cortical surface to be able to stimulate deeper cortex. Nevertheless, Cushing remained convinced that the experimental conditions were too crude, that the experiments were conducted too quickly, and that the findings were subject to more than one interpretation. Furthermore, the electrode Sherrington used was a single or double blunt-pointed platinum wire, which Cushing described as "a large electrode or big shovel." As a power source, Sherrington used two double zinc-cell batteries. The strength of the electrical current used for stimulation was estimated by observing the contraction of an exposed muscle (23) . Toward the end of his stay with Sherrington, however, Cushing appeared to become more curious about the localization of the sensory center in the brain. His curiosity was aroused during his observation and conversation with Sherrington on July 24, and he described the occasion in his diary on July 25, 1901. He noted that the "chimpanzee yesterday responded like a sensory response... ." Each time that a particular cortical area was stimulated, the animal opened its eyes. Sherrington stated "that the stimulated area may be the sensory area." One wonders about the location of the particular cortical area that caused the possible sensory response. Unfortunately, Cushing's diary did not specify its location or relation to the Rolandic fissure. This observation, however, certainly aroused Cushing's curiosity strongly enough to lead him to pursue his own cerebral mapping studies when he returned to Baltimore at the end of the summer of 1901. He began to conceptualize a "narrow motor strip with sensory area immediately behind it." Cushing apparently performed cortical stimulation studies on more than 50 anesthetized patients, and he claimed that his results were in exact accord with Sherrington's findings in anthropoids and with Krause and Frazier's findings in humans (14). On October 18, 1906, at the New York Academy of Medicine, he reported on his own stimulation studies on an anesthetized patient on April 29, 1903 (12). In the same year, 1906, Cushing drew a map of the

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HORSLEY AND SHERRINGTON CLASH On May 6, 1909, Victor Horsley denounced the new conception of the motor cortex at the annual Linacre Lecture at St. John's College, Cambridge. The title of his lecture was "The function of the so-called motor area of the brain" (33). After a lengthy review of the historical understanding of brain function from Aristotle to his own time, Horsley declared that there was no such thing as a pure motor center in the cortex. He declared that the term used should be sensorimotor cortex. If any differentiation in the function were to be made, he said, it should be mainly sensory or mainly motor function. Furthermore, he listed a series of reports on motor responses elicited from the so-called sensory area behind the Rolandic fissure by different investigators (48,50). He further stated that he had constantly demonstrated and published his own experimental evidence to show that a considerable proportion of the "sensory representation" was located in the so-called "motor area" (33). He recalled that, in clinical experience also, cortical anesthesia is always accompanied by some degree of paralysis (16). He claimed that the differentiation between sensory and motor cortex is one of degree, not of kind (33). Furthermore, he disagreed with Campbell's notion that the postcentral gyrus is a pure sensory area because there are no Betz cells in the area posterior to the Rolandic fissure. He pointed out that there are areas of the "motor" cortex where there are no such "motor" (giant pyramidal) Betz cells. For example, Betz cells are lacking in the so-called Sherrington's motor areas for the face, larynx, pharynx, and eye muscles (33,41). Horsley voiced his concern about the new movement toward an idea of pure motor cortex and separate sensory cortex. He stated that although some neurologists still thought of the nervous system as being made up of sensory centers and motor centers (33) , "It appears to me that on this all-important question not only the general principles of Bastian [3] and Jackson [35], but also the original teaching of Munk, are in danger of being overlooked in this country and, perhaps, in America" (33). Nevertheless, according to Penfield (54), despite Horsley's attack, subsequent publication of the work of Sherrington's laboratory (40) forced a change from the idea of a rather broad, overlapping sensorimotor cortex to the conception of a narrow, discrete preRolandic motor cortex, separate from the discrete sensory area. The more decisive comprehensive publication of Sherrington's laboratory findings did not take place until 1917, after Horsley's death in 1916 (he died from sunstroke in Mesopotamia where

he was stationed in the First World War). R. Granit, Professor of Neurophysiology at the Royal Caroline Institute in Stockholm (26), postulated that Sherrington might have delayed publication to avoid another clash with Horsley. Lord Birkenhead, Professor of Medicine at the University of Liverpool (5) , described an earlier clash between Sherrington and Horsley. The clash was triggered by a note, "Experimental Degeneration of the Pyramidal Tract," published in Lancet by Sherrington (57). Sherrington claimed that he had demonstrated pyramidal tract degeneration after making a lesion in the thumb area of the cortex. The note was printed in the journal on February 3, 1894. In a response, Horsley claimed that he had suggested the degeneration experiments to Sherrington but that Sherrington did not succeed and gave up. Furthermore, Horsley had conducted his own work with his assistant, Dr. Mellus (57). They had succeeded where Sherrington had not, and they had submitted their finding to Lancet around Christmas of 1893, 2 months earlier than Sherrington had submitted his note. Sherrington was apparently very hurt by this controversy, and his subsequent publications on the subject were brief or passing references to the motor cortex study, even in his Stilliman lectures at Yale in 1904, which were later published as the Integrative Action of the Nervous System in 1906 (4). [The work at issue between Horsley and Sherrington involved degeneration in the cervical cord after focal resection of the motor cortex. While performing this work in 1893, Sherrington learned that Horsley's laboratory was also working on the problem. Sherrington then quickly wrote his note to Lancet describing his preliminary findings. This upset Horsley greatly. Horsley claimed that first of all, he, Horsley, had suggested the idea to Sherrington sometime earlier and had detailed the plan for the investigation, but Sherrington had failed in the work and Horsley had supposed that he had given up on the study. Horsley claimed that his laboratory had succeeded where Sherrington had failed. Sherrington replied vigorously to Horsley's claim. Horsley then proposed to settle the dispute by submitting all specimens, documents, etc., to impartial arbitrators. But Sherrington declined to accept arbitration. Boyce, then assistant to Horsley, later Professor of Pathology at Liverpool, wrote in a letter (March 6, 1894) to Lancet, "Unfortunately, I understand that the probable reason why Professor Sherrington shrinks from entering into arbitration is that after this controversy began he destroyed the specimens on which his communication to you of February 3rd was based" (57).] Furthermore, probably for the same reason, Cushing's colored sketches of a mosaic motor pattern on the anthropoid brain (drawn from the stimulation studies he observed in 1901 at Sherrington's laboratory) were not published until 1917, and even the publication by Leyton and Sherrington in 1917 included only one plain sketch by Cushing, along with other illustrations from Sherrington's laboratory (Fig. 8). The more elaborate sketches done by Cushing were not included, although by this time the friendship between Cushing and Sherrington had

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map of the sensory cortex in humans seemingly finalized the concept of the pre-Rolandic area as representing motor function and the post-Rolandic area as representing sensory. As if placing a milestone, Cushing for the first time used the term narrow motor strip, and his designation of color codes, red for motor function and blue for sensory cortex, in his celebrated chapter in Keen's surgical textbook (Fig. 6) (13).

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MORE COMPLEX, BROADER CORTICAL REPRESENTATION By the 1930s, electrical stimulation studies on human brain done by Foerster (19) and extensive physiological work by Fulton (22) as well as cytoarchitectural work by the Vogts (61) began a shift again toward belief in a much more complex, broader motor representation (Fig. 11) (68). In 1937, Penfield noted that it was impossible to confine functional representation within Brodmann's areas 4 and 6 (the narrow motor strip) (8,54). In 1952, Woolsey et al. (66) reported in detail their meticulous systematic electrical stimulation study of wide areas, including the precentral and the supplementary motor areas, in Macaca mulatta. They confirmed that the "peri- Rolandic" area has both motor and sensory function. Furthermore, in their study, even after chronic removal of the periRolandic and supplementary motor areas, the postcentral gyrus yielded focal movements (primary motor responses) on stimulation (67). Similarly, primary (focal) motor responses could be elicited from the normal supplementary motor area after complete aspiration of the precentral motor area (67). In 1956, Bertrand's (4) electrophysiological experiments showed a contribution from the supplementary motor area to the pyramidal tract. Levin and Bradford (39) had found that 20% of cells that undergo retrograde degeneration after transection of the corticospinal tract were in the parietal lobe. Woolsey and Chang (65) had also demonstrated that the whole parietal lobe of Macaca mulatta, not just the pre-Rolandic and supplementary motor areas, could be antidromically activated by electrical stimulation of the medullary pyramid. Over the last quarter century, recording of somatosensory evoked potentials after stimulation of the main peripheral sensory nerves in the extremities has shown that sensory evoked responses are seen in a broad area that extends to the so-called preRolandic motor cortex (45) and that it is difficult to define the anteroposterior extent of the sensory and motor area (25,44,52), although a phase reversal occurs at and a relatively rapid drop in amplitude occurs

beyond the central area (44). Thus, despite abundant scientific evidence to support the idea of a broader, overlapping representation of sensorimotor function over the brain, the teaching of Sherrington and Cushing had considerable, lasting influence on the concept of cortical representation. For example, recent neurosurgical textbooks continue to use diagrams showing a narrow motor strip in front of, and a sensory strip behind, the Rolandic fissure (28,46). This historical tendency to localize certain functions to delimited and divided parts of the brain continues to influence current teaching and to promote the misleading conception that both animal and human brains have a narrow peri-Rolandic strip that contains primary motor and sensory cortical representations (10). As noted earlier, the potential for this misconception arose in Sherrington's studies, which directly transferred animal cortical mapping studies onto human brain maps without accounting for possible interspecies differences. In addition, Sherrington's animal experiments were done under "deep anesthesia," and the resulting sedation clearly could have modified the animals' cortical responsiveness. Furthermore, according to recent surgical microscopic dissection of human brain by Harkey et al. (29), the convolutions of the cerebral hemispheres vary from brain to brain and even between the two sides of the brain. Yet, in spite of the near impossibility of identifying the Rolandic fissure on the partially exposed human brain, the presumed anatomical fissure has been used as a distinctive dividing line for physiological brain mapping. For example, Cushing (13) used the Rolandic fissure identified through the partially exposed brain surface. He expressed some uneasiness about the complexity of identifying the fissure, stating, "The Rolandic fissure is not a straight line, but is broken into two, or sometimes three lines." Nevertheless, Cushing concluded that the motor cortex is limited to a narrow strip--1.0 cm of the exposed part of the gyrus centralis anterior. Similarly, Penfield plotted his patients' responses along a common single drawing of the human brain, with the same hypothetical Rolandic fissure used for all patients. The starting point of the Rolandic fissure was identified by electrical stimulation (54). Penfield stated, "The stimulation study proceeded along the sulcus (fissure), with eventual outlining of the fissure of Rolando . . . it is usually best to outline the Rolandic fissure thus before exploring further" (54). This approach carries the risk that the exploration will be confined within a limited, narrow zone that follows the assumed Rolandic fissure. Once a motor response occurs, the sulcus posterior to the stimulated site is assumed to be this fissure. Such an approach does not in itself exclude the possibility that a motor response might occur anterior to other fissures as well. Because anatomical identification of the Rolandic fissure can be difficult, particularly on brain partially exposed by craniotomy, and because the location of both the Rolandic fissure and the motor

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grown firmer, as is evidenced by the numerous letters they exchanged (5,17,23,26). They met frequently at medical and scientific meetings (Fig. 9) (24). Cushing later published his colored sketches in his own book, Meningiomas, published in 1938 (Fig. 10) (15). Cushing's account of the delay in the publication of these sketches is rather circumlocutory (15). He stated "These drawings have remained inserted in a notebook covering an eventful period of training under an inspiring master. Why they were never used is not now recalled. The proposal may possibly have been made that before publication they be checked, when opportunity offered, by similar observations on man." Cushing continues, "If this was the understanding, only one small effort in this direction came, in 1909, to fruition." He was referring to his publication in 1909 on "The Faradic Stimulation of the Postcentral Gyrus in Two Conscious Patients" (14) .

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16. A related article will appear in the next issue of Neurosurgery. 17. Received for publication, July 26, 1991; accepted, final form, December 17, 1991. Reprint requests: Sumio Uematsu, M.D., Department of Neurosurgery, The Johns Hopkins University, 601 North Wolfe Street, Baltimore, MD 21205.

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ACKNOWLEDGMENTS We thank Edward T. Morman, Ph.D., Librarian of the Department of History of Medicine, and his staff for their search for invaluable books and articles during preparation of this work. We also thank the staff of The Welch Medical Library for gathering most of the older volumes of Gray's Anatomy (Volume 2, 1861 to Volume 27, 1959) and A Reference Handbook of the Medical Sciences (Buck AH, New York, William Wood and Co., 1885 to 1923, 33 volumes) for review. This work was supported in part by NINDS RO1 NS 26553 and by grants from the Seaver Foundation, The Whittier Foundation, and McDonnell-Pew Program in Cognitive Neuroscience.

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cortex may show individual variation, some surgeons have recently adapted an extraoperative stimulation approach for identification of critical cortical areas for motor and sensory function (25,45,59). The approach uses sequential consecutive stimulation to exclude a potentially directed (biased) stimulation-point selection process (45). The subdural grid allows systematic stimulation of the entire area of the cortex covered by the large electrode array. Location of a sulcus presumed to be the Rolandic fissure does not influence the stimulation process. Recent studies using the grid approach support the concept of a broader and much more complex cortical representation for both motor and sensory function (45,59,60) . It may be best to conclude this review with the observation made by Crosby et al. (11) in 1962 that the degree of localization of function in the cortex has probably been overemphasized. These authors note that although a localization pattern is present in the cortex, it should be expected to be less than the localization found in the peripheral nervous system, spinal cord, brain stem, or thalamus (6,49,55). Perception of cutaneous sensations (e.g., temperature or tactile) at cortical levels is actually the function of interactions of whole neurons in the cortex (53,63). Thus, it is not surprising that the cortical representation demonstrated upon artificial activation of the cortex by electrical stimulation is more complex, variable, and broader than originally thought.

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COMMENTS This is an excellent article by Dr. Uematsu and his colleagues offering a historical perspective on scientific efforts to localize the sensorimotor cortex. From this outlook, the authors have described several patterns for consideration. First, experimental techniques must be outlined accurately to allow for a comparison of data. Second, the jump from experimental observation in animal models to human

behavior may be risky and subject to considerable variation. Third, dogmatic interpretation of scientific data, particularly data subject to differences in experimental techniques, may lead to inappropriate deductions. Finally, earlier investigators with agile minds and less sophisticated techniques managed to arrive at conclusions similar to modern concepts and their clinical implications. All in all, the article is a valuable historical introduction for surgeons interested in exploring mechanisms of cortical function. William C. Hanigan Peoria, Illinois. Cerebral localization is one of the most fascinating, colorful, and often controversial chapters in neurological history. The authors have given us insight into the birth and the development of this rather complex topic. Perhaps the most important stimulus to bring forth attempts at cerebral localization was the search for the site of mental functions and the seat of the soul. Franz Josef Gall (1758-1828) is quite often only remembered as the founder of phrenology. The mention of this topic today can evoke laughter and disgust. But the authors have reminded us of the contributions that Gall made to neuroscience. The concept that mental traits were correlated with the configuration of the cortex appears to have been made first by Gall. He looked upon the cerebral cortex as the organ of the mind. His lectures were stopped by the Austrian Government on the grounds that they were dangerous to religion. He was branded as a materialist and banished from Vienna by Francis II, Emperor of Austria. Gall, however, continued to teach and practice phrenology in Germany, but not without criticism (1,2). John Hughlings Jackson believed that the manifestations of epilepsy would play a key part in understanding the functions of the nervous system. It was Eduard Hitzig and Gustav T. Fritsch who would later confirm the conclusions set forth by Jackson. It is interesting to note that Fritsch's interest in localization may have been aroused when he observed contralateral twitching in the limbs of a soldier with a head injury in the Prussian-Danish War of 1864 (3,4). It is also noteworthy that the experiments of these two young Germans were performed in Hitzig's bedroom (4). Here they stimulated the cerebral cortex of a dog with a pair of blunted electrodes. The authors have given Fritsch and Hitzig credit for the first electrical stimulation of a mammalian cerebral cortex. This is not entirely the case. It was Robert Bentley Todd, a British neurologist, who performed galvanic stimulation experiments on rabbits in 1849 (7). His experiments were apparently not known to Fritsch and Hitzig and may have been overlooked by Ferrier (4). Cerebral localization and the introduction of aseptic surgery ushered in a new era in cerebral surgery. It was Paul Broca who first neurologically localized an intracranial lesion (extradural abscess) and then operated on the patient. Unfortunately, his

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tetanus toxin. J Physiol 34:316-331, 1906. Sherrington CS: Note on experimental degeneration of the pyramidal tract. Lancet 1:370, 501, 571, 1894. Temkin O: Gall and the phrenological movement. Bull Hist Med 21:275-321, 1947. Uematsu S: Individual variations and broad representation of motor and sensory cortex in humans. Epilepsia 30:643, 1989 (abstr). Uematsu S, Lesser R, Fisher R, Krauss G, Hart J, Vining EP, Freeman J, Gordon B: Resection of the epileptogenic area in critical cortex with aid of a subdural electrode grid. Stereotactic Funct Neurosurg 54:34-45, 1990. Vogt C, Vogt O: Die vergleichendarkitektonische und die vergleichendreizphysiologische Felderung der Grossbirnrinde unter besonderer Berucksichtigung der Menschlichen. Naturwissenchaften 14:50, 1191, 1926. Walker AE: The development of the concept of cerebral localization in the nineteenth century. Bull Hist Med 31:99-121, 1957. Walshe FMR: On the interpretation of experimental studies of cortical motor functions with special reference to the "operational view" of experimental procedure. Brain 74:249-266, 1951. Wilkins RH: Electrical excitability of the cerebrum (English translation of ref. 17), in Wilkins RH (ed): Neurosurgical Classics. New York, Johnson Reprint Corp., 1965, pp 16-27. Woolsey CN, Chang HT: Activation of the cerebral cortex by antidromic volleys in the pyramidal tract. Res Publ Assoc Res Nerv Ment Dis 27:146-161, 1948. Woolsey CN: Settlage PH, Meyer DR, Spencer W, Pinto-Hamuy T, Travis AM: Patterns of localization in precentral and supplementary motor areas and their relation to the concept of a premotor area. Res Publ Assoc Res Nerv Ment Dis 30:238-264, 1952. Woolsey CN: Organization of somatic sensory and motor areas of the cerebral cortex, in Harlow HF, Woolsey CN (eds): Biological and Biochemical Bases of Behavior. Madison, WI, University of Wisconsin Press, 1958, pp 63-81. Zulch KJ: Critical remarks on "Lokalisationslehre," in Creutzfeld O, Galbraith GC (eds): Cerebral Localization. New York, Springer-Verlag, 1975, pp 3-16.

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57.

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T. Glenn Pait Morgantown, West Virginia

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patient did not survive (9). It was in the United States that the first attempts to stimulate a human brain were performed. This honor goes to Roberts Bartholow (1831-1904), Professor of Materia Medica and Therapeutics of the Medical College of Ohio and Physician to the Good Samaritan Hospital, Cincinnati, Ohio. A 30-year-old woman with a 13-month history of "epithelioma" of the scalp and erosion of the underlying skull was admitted to the Good Samaritan Hospital on January 26, 1874. Bartholow had studied the works of Fritsch and Hitzig as well as Ferrier. He apparently saw a "window of opportunity" and convinced the young woman to consent to stimulation of her brain with both galvanic and faradic currents. He obtained contralateral movements of her arms and legs with stimulation over the cerebral cortex. Unfortunately, the woman developed persistent seizures and meningitis and died several days after the stimulation was started (2). His attempt at taking advantage of a window of opportunity was not as well received as William Beaumont's work in gastric physiology, and, like Gall, he displeased his colleagues and was forced to leave the city. W. W. Keen was also involved in cerebral localization with electrical stimulation. The celebrated An American Textbook of Surgery for Practitioners and Students, edited by Keen and White (both of Philadelphia), acknowledged the work of Horsley and Schäfer. In the first three editions of this textbook, the position of the motor areas of the brain of the monkey, as determined by Sir Victor Horsley and his associate, Schäfer (5), was included. It is in the fourth edition of this textbook that Keen has his own drawings (6). Cerebral localization gave hope to the development of a means of localizing brain lesions through an intact skull. This clinical observation/localization brought forth a new era in surgery. The problem now facing early surgeons brave enough to explore intracranially was where to trephine. Numerous anatomists, neurologists, and surgeons began to establish guidelines for cranial measurements that would allow the surgeon to operate on that area of the brain, guided by cerebral localization. This list includes Broca, Lucas-Championnière, Sequin, Nancrede, and Mills (1). These cranial measure-ments were quite complex and could not guarantee exact localization. In fact, Ashhurst (1) stated that these attempts at cerebral localization were not as useful as were first anticipated. The authors have shared with us the relationship between Sherrington and Cushing. It is not surprising that Cushing was the first to apply colors to areas of cortical localization. Wilder Penfield mapped numerous responses of the brain via electrical stimulation. Yet, when he was asked about Hughlings Jackson's "Highest Level," he stated he could only say, "There is nothing to suggest that it is in the cerebral cortex" (3,8).

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Figure 1. The first human brain map, made by Ferrier in 1876. The map, however, was derived from animal brain stimulation studies. 1, center for leg and foot; 2, 3, 4, centers for complex movements of arms and legs; 5, 6, centers for the arm and hand; 7, 8, center for the mouth; 9, 10, centers for the lips and tongue; 11, center for the mouth; 12, center for the eyes; 13, center for vision; 14, center for hearing; a, b, c, d, centers for the movement of the wrists and fingers (18).

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Figure 2. Victor Horsley's brain maps, drawn in 1887. These maps were adapted in the first American edition of Gray's Anatomy, edited by W. W. Keen, a leading surgeon of his day. Keen stated in the preface to the edition: "I have added a section on cerebral localization and topography--subjects of great and increasing importance, especially in view of the recent rapid strides in cerebral surgery" (36).

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Figure 4. Mills' human brain map, drawn in 1888. Note the subdivision of the motor areas, extending in front of and behind the Rolandic fissure (47).

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Figure 3. Keen's "double brain electrode" used during his earlier brain surgeries in 1888. A faradic battery generating a current sufficient to stimulate the thenar muscles was usually employed (38). The probe consisted of a rubber handle and two partially insulated poles.

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Figure 6. Human brain map drawn by Cushing in 1906, with the red-colored motor area in front of and the blue-colored sensory area behind the Rolandic fissure. At the time that this drawing was made, Cushing had not conducted brain stimulation studies on conscious patients. The stimulation study for sensory examination took place 2 years later (13).

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Figure 5. One of Cushing's many drawings of a chimpanzee's brain, with notations of the body parts eliciting motor responses to faradic stimulation at Sherrington's laboratory in 1901. The drawing was not published until 1917 (40).

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Figure 7. One of Cushing's two sketches to show the area of sensory responses in relation to the central (Rolandic) fissure. Note the flexion of thumb (motor area) in front of the prominent vein (central, Rolandic fissure) and sensation of hand and finger areas immediately behind the vein (14).

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Figure 8. Gruenbaum and Sherrington's map of the chimpanzee brain. The motor area is confined strictly in front of the sulcus centralis (Rolandic fissure) (40). This map, with an undisputed line for the sulcus centralis (Rolandic fissure), became the standard for teaching that the Rolandic fissure served as the dividing line, with motor cortex in front of it and sensory cortex behind it.

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Figure 10. Cushing's sketch of the chimpanzee brain with a mosaic pattern of motor representation, drawn during his visit to Sherrington's laboratory in 1901. Sherrington never published the drawing, but Cushing included it in his well-known book, Meningioma, in 1938 (15).

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Figure 9. Harvey Cushing and Charles Sherrington "probably at Harvard in 1927," according to Granit (26). (Another photograph, apparently taken by John Beattie at the Royal College of Surgeons on July 12, 1938, according to Fulton (24), has an identical background, so the place and ages of the men are not certain.)

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Figure 11. Foerster's human brain map. Foerster worked closely with C. Vogt and O. Vogt (61), who were carrying out a cytoarchitectural study on human cortex. According to Zulch, every weekend Foerster and the Vogts exchanged information from Foerster's brain stimulation study and the Vogts' histological cytoarchitectural study in order to examine the correlations (68). Note that Forester's map uses the Vogts' cytoarchitectural numbering system. After consultation with Fulton, Foerster designated areas 4 (in solid black), 6, 3, 1, and 2 (horizontally lined areas) as primary motor cortex. Areas 6a, 6b, 5a, 5b, and 22 are extrapyramidal cortex (19).

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Table 1. Extent of Motor Cortex at the Rolandic Region

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Localization of sensorimotor cortex: the influence of Sherrington and Cushing on the modern concept.

According to Penfield, the work of Charles Sherrington's laboratory forced a change from the long-held concept of a broad, overlapping sensorimotor co...
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