HoP Chapter 3: Textbook Aristotle: - greatest biological thinker of ancient Greece Downplayed importance of the heart The physical brain was unimpressive to him Refused to believe what appeared to be bloodless, insensitive, and generally uninspiring mass could be the seat of the highest human facilities – assigned this role to the heart Saw brain as minor “condenser” of the vapors emanating from overheated humors that rose to the top of the body (cerebrospinal fluid of the ventricles) Ancient Chinese Culture: The spirit and soul resided in the heart Early translated texts by Chinese Scholars, Mental philosophy = study of heart & spirit Descartes: - Localized some important functions in the brain but did not believe a perfect & unified entity like the rational soul could be housed in a divided structure like the brain Descartes called cerebrospinal fluid “animal spirits” Pineal gland = where Descartes believed was the most likely point of interaction between body & mind 100 years after his death, the brain would become the center of considerable attention as researchers attempted to understand its role in mental life. When Descartes skull was examined and found deficient in the regions for reason & reflection, some phrenologists retorted that the philosopher’s rationality had always been overrated. Franz Josef Gall (1758-1828): - Controversial German physician Among the 1st scientist to regard the entire brain as a complex organ responsible for the higher mental functions Reputation as a brilliant anatomist of the brain Built on earlier works by Locke’s old teacher, Thomas Willis Using new, delicate dissection techniques, he confirmed & developed many of Willis’s basic findings regarding grey & white matter Found that the 2 halves of the brain are interconnected by stalks of white matter (nerve tissue) = commissures Smaller tracts of white fibers cross over from each side of the brain to connect with the opposite sides of the spinal cord - - - - 1st great comparative brain anatomist (carefully examined/compared brain similarities/differences in animal species & differing human types These studies showed that higher mental functions correlated with the size & health of the brain – particularly its outer surface or cortex (we will see later that this correlation is imperfect/misleading) Gall’s anatomical findings lead to discovery that the brain & spinal cord are composed of billions of nerve cells = neurons (each with an electronically active cell body/nucleus) Speculated that specific parts of the brain were the seats of specific functions (large area = function it housed should be strong) Had no direct way of observing a living person’s brain – had to make important, questionable assumptions “Gall’s Passionate Widow” - emotionally, erratic patient – lead Gall to believe her cerebellum (structure at base of the brain) was unusually developed due to her well-developed neck & skull base) The major weaknesses of Gall’s phrenological theory: o 1st) Incorrectly assumed the shape of skull accurately reflects the shape of underlying brain o 2nd) Gall’s choice of specific psychological qualities to localize within the brain – a collection of 27 “faculties” located in specific brain areas called “organs” o 3rd) unreliable methods by which its hypotheses were often tested. Gall always maintained that his theory was based on observation, a claim literally true but unreflective of the selectivity and arbitrariness of many of the observations. At death, Gall’s skull was twice as thick as the average! Thomas Willis (1621-1675): - - 1664 Willis published the 1st accurate & detailed description of the brain’s complex physical shape, illustrated with plates by the celebrated architect Christopher Wren Willis emphasized the substance of the brain’s various structures rather than its spaces & the fluids that filled them (in speculating about how the brain functions) Observed that brain tissue was not undifferentiated, as Aristotal thought, it consisted of 2 kinds of substances: o 1) a pulpy gray matter occupying the outer surface, the inner part of the spinal cord, and several discrete centers within the brain o 2) a fibrous white matter in the other regions; Willis speculated that the white matter consisted of narrow canals whose function was to distribute “spirits” generated in the gray matter. Willis also accurately described the blood vessels of the brain - establishing firmly that the living brain was far from a bloodless organ Other physicians after Willis discovered that localized interruptions to the brain’s blood supply could cause apoplexy = stroke Neurons are interconnected by dendrites (receive signals from other neurons; long fibrous axons transmit signals to other neurons) Axons cluster together to form the brain’s white matter, while the call bodies & dendrites constitute the gray matter. Phrenology = science of the mind (Greek phrenos, “mind”) Physiognomy = the reading of a person's character in his or her physical features (big and bulgy eyed children from Gall’s childhood – memorizers who got good grades) Craniometry = the measurement of the physical dimensions of the skull Traveling phrenologists would set up in hotels and local shops offering detailed readings (gave guidance, marital advice/counselling, child-rearing advice) Most in the scientific community considered phrenology as a joke Johann Kasper Lavater (1741-1801) - Swiss mystic & theologian Promoted the art of physiognomy during the 1770’s - remained a popular pastime throughout the 1800’s Pierre Flourens (1794-1867) - - Young French scientist Conducted a series of experiments Contrasted dramatically with Gall Graduated from a famous medical school at 19 yo Protégé of Georges Cuvier 9most celebrated scientist in France, “Doctor of Biology) Appalled by the undisciplined observational strategies of the phrenologists Studied function of the brain strictly according to experiment – he would systematically manipulate specific variables & carefully observe the resulting effects. He used a technique called Ablation = the surgical removal of specific small parts of an animal’s brain - in order to observe any changes in behavior or function Did not invent Ablation, but refined it greatly Carefully nursed animals he experimented on back to as healthy as possible before drawing conclusions (avoid confusion) Believed his findings demolished phrenology Actions initiated by the “will” in the cortex had to be out together and integrated by the cerebellum, & the loss of coordination caused by damage to the cerebellum had to be dealt with by the voluntary reactions in the cortex Action propre = specific action Action commune = common action Saw the brain as the seat of an integrated & harmonious soul - In the 1860’s new findings suggested that Flourens’s meticulous experiments had failed to detect some important localized functions in the cortex – and the fact that he had overemphasized the unity of the brain’s functioning - During the height of the Flourens’s influence, one phrenological localization continued to attract some interest and support from the vocal minority of doctors: the placement of verbal memory in the brain region directly behind the eyes These physicians studied loss of speech after strokes and other brain injuries Jonathan Swift: Wrote Gulliver’s travels; following a stroke a year before dying, Swift lost ability of speech yet seemed to understand what was communicated to him, he at times could communicate when emotions ran high (once at a servant, and another when he was upset with himself) Another case: a priest suffered a stroke and lost speech except for a curse word emotion-laden exclamations by Swift and this priest demonstrated the muscles necessary for producing speech could still function, even though they had somehow lost the capacity for regular speaking - - Jean Baptiste Bouillaud (1796-1881) - Rejected much of phrenology – but felt there was some truth to the notion of an area that controls language in the frontal region on the cortex Spoke out at medical meetings and offered to pay 500 francs to anyone who could demonstrate a case of severe frontal lobe damage unaccompanied by speech disorder (no one took him seriously enough to accept challenge) Ernest Aubertin (1825- 1893) - - Bouillaud’s son-in-law Physician Found a patient whose symptoms did support Bouillaud’s theory - a soldier wounded by gunshot on the left front of head had recovered completely except for a soft spot in his skull at the point of the wound. When the soft spot was gently pressed – he lost his normal power of speech (some skeptics on if the patient was being truthful or not) Aubertin believed in that patient’s sincerity & mounted a defense of his father-in-law's theory When presenting his views at the Paris Anthropological Society in 1861, he precipitated one of the critical incidents in the history of brain science Paul Broca and the Case of “Tan” - Paul Broca (1824-1880) Chief of surgery at a major Parisian hospital Through surgical work, he became interested in variations in people's skeletal structures, particularly skulls Invented several instruments for measuring skulls - - - - 1859: founded the Paris Anthropological Society to bring together other people with similar interests (several experts joined including Aubertin) Today’s terminology, this area of study = part of physical anthropology opposed to cultural anthropology Aubertin found an incurably ill patient, lost speech previously, retained ability to understand language. Aubertin announced he will perform an autopsy after his death, declared if frontal areas were intact, he would renounce his position on the importance of that brain area to speech TAN – similar patient as to Aubertin’s incurable one ended up on Broca’s surgical ward; he had no family or support and was hospitalized; no speech; terminally ill with gangrene in leg, remained otherwise healthy & intelligent; communicated with fingers and pointing to things, his only vocalization was “tan” leading to the nickname “Tan”. After his death, brain autopsy by Broca found an egg sized portion of the left hemisphere was damaged, with the center nearing Gall’s organ of verbal memory One confirming case did not prove a theory, of course Broca continued, with difficulty as he could not create experimental brain lesions (injuries/ablations) in humans as Flouren’s had with animals & cases of both speech deficits & brain autopsies were rare! Proved his worth as a scientist by collecting more supportive evidence Found autopsy info from several cases that followed Brain damage in autopsies had varied, but almost always included the same region of frontal lobe - Surprise finding: in right-handed patients the damage always occurred on the left side (Broca’s area) After debate, the speech debility from damage to that area was named aphasia (after the term used by Plato to denote the state of being at a loss for words) Broca became 1st established figure to successfully challenge Flourens’s conception of the undifferentiated or unified cerebral cortex Broca’s findings lead to new period interest in localized function of the brain - “new phrenologists” - discovered many important localizations Broca promoted the idea of the superior white European male brain (larger than average) - not proven (haha) Sensory and Motor Areas - - - 1870: two young German physiologists, Gustav Fritsch (1837-1927) & Eduard Hitzig (1838-1907) had idea that the brain might not be the totally insensitive organ Aristotle thought & that it may respond to direct electrical stimulation. Recent discoveries on the electrochemical nature of nerve signals made this idea plausible Together these two physiologists did surgery on a dog’s cortex and applied mild electricity to various points (this would not be approved today... Ethics!) RESULTS from dog brain: revolutionized brain science; Fritsch & Hitzig discovered stimulation to specific points in region no known as the motor strip elicited movements on opposite side of body Many followed their lead including... David Ferrier (1843-1928) - - Demonstrated the presence of many functionally distinct “centers” in the cortex in the 1870’s Electrically stimulated the occipital lobe on monkey’s brain – eyes moved rapidly & synchronously (as if looking for something) Ablation in the occipital lobe produced blindness but no other senses affected The occipital cortex contained visual area Also discovered an auditory area the temporal (side) lobe Discovered a strip behind the motor strip associated with sensory functions for the same body parts. Ablations to this sensory strip produced a loss of sensitivity in specific parts of the body. While ablations of the bordering motor strip caused paralysis These findings confirmed the reality of cortical localization, they also conclusively undermined the old phrenology Broca’s area resembled Gall’s organ of verbal memory in some ways Brain parts rich in white matter = association areas frontal lobes of humans very large compared to other species, rich in white matter, speculated to contain the large association areas responsible for humans’ superiority over other animals in thoughtfulness & intelligence Wernicke’s Theory of Aphasia - - - Carl Wernicke (1848-1905) Young German neurologist Used this new conception of the brain as basis of influential theory of aphasia Noted: Broca’s area lay directly in front part of the motor strip responsible for movement of the mouth, tongue, and face Following this, localized damage to Broca’s area alone should theoretically afflict the memory for spoken words but NOT the physical capacity for speaking (this could account for cases like Jonathan Swift and Tan) He had 10 patients with a very different sort of language disorder = sensory aphasia to contrast motor aphasia previously investigated by Broca These 10 patients could speak fluently with correct grammar, but their understanding of spoken language was severely impaired, & speech was marked by many peculiar words & mispronunciations, which Wernicke called paraphasia (occurs after brain damage)
