Download Week 1a Lecture Notes

Phrenology and Localization
Franz Joseph Gall
(1758-1828)
Gall’s method: Correlating variations in character with
variations in craniological signs.
Moral and intellectual faculties depend on the physical
structure of an individual brain. Relative development
(usage) results in differential growth. Brain is an
“collective” of many faculties and their physical
counterparts.
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Phrenology and Localization
A summary of Gall’s view of the brain:
1. The brain is the organ of the mind.
2. The mind is composed of multiple distinct, innate faculties.
3. Because they are distinct, each faculty must have a separate seat or "organ" in the brain.
4. The size of an organ, other things being equal, is a measure of its power.
5. The shape of the brain is determined by the development of the various organs.
6. As the skull takes its shape from the brain, the surface of the skull can be read as an accurate index of
psychological aptitudes and tendencies.
Gall’s original 27 faculties:
1. impulse to propagation (Zeugungstrieb, Fortpflanzung; Instinct de la génération, de la reproduction, de la propagation); 15. faculty of language
(Sprachsinn, Sprach-Forschungs-sinn; sens de langage, Talent de la philologie); 2. Tenderness for the offspring, or parental love (Jungenliebe,
Kinderliebe; Amour de la progéniture); 16. disposition for colouring, and the delighting in colours (Farbensinn; sens des rapports de couleurs); 3. friendly
attachment or fidelity (Anhänglichkeit, Freundschaftsinn; Attachement, amitié); 17. sense for sounds, musical talent (Tonsinn, Musiktalent; Talent de la
musique, sens des rapport des tons); 4. valour, self-defense (Mut, Raufsinn, Selbstverteidigungsinstinkt; Instinct de la défense de soi-même et de sa
propriété); 18. arithmetic, counting, time (Zahlensinn, Zeitsinn; Sens des rapports des nombres); 5. murder, carnivorousness (Mord/Würgsinn; Instinct
carnassier); 19. mechanical skill (Kunstsinn, Bausinn; Sens de mécanique, de construction, Talent de l'architecture); 6. sense of cunning
(Schlauheitssinn, List; ruse); 20. comparative perspicuity, sagacity (vergleichender Scharfsinnorgan; Sagacité comparative); 7. larceny, sense of
property (Diebessinn, Eigenthumsinn; Sentiment de la propriété); 21. metaphysical perspicuity (Metaphysischer-Tiefsinn; Esprit métaphysique,
profondeur d'esprit); 8. pride, arrogance, love of authority (Stolz, Hochmut, Herrschsucht; Orgueil, fierté, hauteur); 22. wit, causality, sense of inference
(Witz, Causalität, Folgerungsvermögen; Esprit caustique); 9. ambition and vanity (Eitelkeit, Ruhmsucht, Ehrgeiz; Vanité, ambition, amour de la gloire);
23. poetic talent (Dichtergeist; Talent poétique); 10. circumspection (Behutsamkeit, Vorsicht, Vorsichtigkeit; Circonspection); 24. Good-nature,
compassion, moral sense (Gutmüthigkeit, Mitleiden, moralischer Sinn; Bonté, compassion, douceur); 11. aptness to receive an education, or the
memoria realis (Erziehungs-Fähigkeit, Sachsinn, Sachgedächtnis; mémoire des choses et des faits, perfectibilité); 25. Mimic (Nachahmungssinn;
Faculté d'imiter, mimique) 12. sense of locality (Ortsinn, Raumsinn; Sens des localités); 26. Theosophy, sense of God and religion (Organ der
Theosophie, Sinn für Gott und die Religion; Sentiment religieux); 13. recollection of persons (Personensinn; mémoire des personnes); 27. Perseverance,
firmness (Organ der Festigkeit, Beständigkeit; Fermeté, constance, persévérance). 14. faculty for words, verbal memory (Wortsinn, Wort-Gedächniss;
sens des mots, mémoire verbale);
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http://pages.britishlibrary.net/phrenology/
The extreme localizationist view.
How do we test this?
In-class project.
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Broca’s Brain
Patient Tan’s brain
Pierre Paul Broca
(1824-1880)
B = Broca’s area of motor speech; A = sensory speech center of Wernicke;
Pc = area concerned with language (after Wernicke)
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Patient Tan
“When the patient was admitted to Bicêtre, at the age of 21, he had lost, for a some time,
the use of speech; he could no longer pronounce more than a single syllable, which he
ordinarily repeated twice at a time; whenever a question was asked of him, he [p. 236]
would always reply tan, tan, in conjunction with quite varied expressive gestures. For this
reason, throughout the hospital, he was known only by the name of Tan. […] The state of
intelligence could not be exactly determined, but there is evidence that Tan understood
almost everything that was said to him. Not able to express his ideas or his desires other
than by the movement of his left hand, he often made incomprehensible gestures. The
numerical responses were the ones he made best, by opening or closing his fingers. He
would indicate, without error, the time on a watch to the second. He knew exactly how
many years he had been in Bicêtre, etc. [p. 237] However, many questions to which a
man of normal intelligence would have found the means to respond by gesture, remained
without intelligible response; other time the response was clear, but did not answer the
question. Undoubtedly, then, the intelligence of the patient had been affected to a great
degree [atteinte profonde], but he maintained certainly more of it than was needed for
talking.”
Paul Broca (1861) Loss of Speech, Chronic
Softening and Partial Destruction of the
Anterior Left Lobe of the Brain.
Bulletin de la Société Anthropologique, 2, 235-238
http://psychclassics.yorku.ca/Broca/perte-e.htm
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Broca on Localizationism
There are in the human mind a group of faculties and
in the brain groups of convolutions, and the facts
assembled by science so far allow to state […] that the
great regions of the mind correspond to the great
regions of the brain.
Paul Broca
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Carl Sagan on Broca
Scientists infer the development of Broca's area from
the inside of hominid skulls…
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The Nissl Stain
stains cell bodies throughout the brain
Nissl stain of the six layers
of cerebral cortex
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Brodmann’s Brain Maps
Korbinian Brodmann
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Brodmann’s Map of the Human Cortex
BA17
BA18
Brodmann’s cytoarchitectural map of human cortex (1909)
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Brodmann’s Maps
Brodmann, K., Vergleichende Lokalisationslehre der Grosshirnrinde in ihren Prinzipien dargestellt
auf Grund des Zellenbaues. Leipzig: J.A. Barth, 1909.
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Brodmann’s View of Localization
Brodmann on the connection between cytoarchitechtonics and regional
functional specialization:
"The specific histological differentiation of the cortical areas proves
irrefutably their specific functional differentiation--for it rests as we have
seen on the division of labor--the large number of specially built structural
regions points to a spatial separation of many functions and from the
sharp delineation of some fields there follows finally the sharply delimited
localization of the physiological processes which correspond to it“
K. Brodmann, in “Some Papers on the Cerebral Cortex”, 1909
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Golgi and Cajal
Santiago Ramon y Cajal (1852-1934)
Camillo Golgi (1843-1929)
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The Golgi Stain
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Cajal’s Neuroanatomy
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The “Neuron Doctrine”
Theodor Schwann (1839):
“Cell Theory” (all tissues of the body are composed of cells)
Wilhelm Waldeyer (1891): “The nerve cell is the anatomical, physiological,
metabolic and genetic unit of the nervous system”. Coined the term “Neuron” ->
“neuron theory”.
Cajal’s studies using Golgi stain: neurons are discrete entities that interact by
“contact”
Golgi’s view was different: Nervous tissue forms a syncytium, nerve cells are not
bounded (“reticular theory”)
Cajal also proposed the “Law of Dynamic Polarization” (neurons as directed
structures with dendrite, soma, axon)
Sir Charles Sherrington: coins the term “synapse” in 1906.
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Lashley and Mass Action
Mass action: reduction in learning is proportional to the amount of
tissue destroyed, and the more complex the learning task, the more
disruptive lesions are.
Equipotentiality: all cortical areas can substitute in supporting
learning.
Lashley picked the wrong task (maze learning). Its complexity allowed
for multiple areas to become involved and therefore compenstate. 17
Stephen Kosslyn on localizationists vs holists:
The mistake of early localizationists is that they tried to map behaviors
and perceptions into single locations in the cortex. Any particular
behavior or perception is produced by many areas, located in various
parts of the brain. Thus, the key to resolving the debate is to realize that
complex functions such as perception, memory, reasoning, and
movement are accomplished by a host of underlying processes that are
carried out in a single region of the brain. Indeed, the abilities
themselves typically can be acccomplished in numerous different ways,
which involved different combinations of processes…. Any given
complex ability, then is not accomplished by a single part of the brain. So
in this sense, the globalists were right. The kinds of functions posited by
the phrenologists are not localized to a single brain region. However,
simple processes that are recruited to exercise such abilities are
localized. So in this sense, the localizationists were right.
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Gestalt Phenomena
Proximity
Continuity
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Gestaltism or Behaviorism?
“I found, somewhat to my amusement, that there were two schools in
this field [animal psychology], of whom the most important
representatives were Thorndike in America, and Köhler in Germany. It
seemed that animals always behave in a manner showing the
rightness of the philosophy entertained by the man who observes
them. […] Animals observed by Americans rush about frantically until
they hit upon the solution by chance. Animals observed by Germans
sit still and scratch their heads until they evolve the solution out of their
inner consciousness.''
Bertrand Russell
(An Outline of Philosophy, 1927, page 241)
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Overview of Unit 1
Cellular structure, membrane potential, AP, synaptic
transmission
Integration of synaptic inputs, synaptic and cellular
plasticity
Methods of cognitive neuroscience, functional
neuroimaging, EEG, TMS, MEG
Data analysis methods, neural coding, computational
neuroscience
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What is the goal of learning about neurons?
Neurons are small and stupid.
The brain is large and smart.
Neuronal activity is simple.
Behavior is complex.
How does knowledge about neurons help us
understand complex behavior? Discuss.
Related questions: Why should we care that our models
are biologically plausible? Isn't it enough that they
predict behavior and are testable?
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Cellular Components
of the Brain
Neurons form densely connected
networks and communicate via spikes.
Glia provide trophic and structural
support.
Some Data on the Cerebral Cortex
Total
Total
Total
Total
Total
Volume
1035 ml
Surface Area
165,800 mm2
Number of Neurons
8.3 x 109
Number of Connections
6.6 x 1013
Wiring Length
107,600,000 m
Source: Murre and Sturdy, Biol. Cybern. 73, 529, 1995.
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Can we know a Grain of Salt?
In a grain of salt (1 microgram), which is just visible
to the naked eye, there are:
1016 sodium and chlorine atoms
(10,000,000,000,000,000)
10 million billion atoms
Connections in the brain: 6.6 x 1013
Could store about 1 percent of the information in a
grain of salt.
But an absolutely pure crystal of salt is regular:
Sodium, chlorine, sodium, chlorine
Describe with 10 bits of information.
Structure is critical. How do neurons represent it?
Source: Carl Sagan, Broca's Brain
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Brain States
There are:
Connections in the brain: 1014
Assume each brain connection is either active (1)
or inactive (0). The number of possible states of
Particles in the Universe: 1080
the brain is:
States of the brain 2
In matlab:
»2^(10^14)
ans =
Inf
1014
Many more brain states than
particles in the universe. But
we'd need a brain at least as
big as the universe to code all
the relations between all the
particles.
Bad french movie translation (Amile):
More neurons in the brain than atoms in
the universe.
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The Neuron
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Dendrites
Dendrites of a single neuron =
dendritic tree.
Dendrites are covered with
thousands of synapses (see
previous picture).
Postsynaptic membrane (part of
dendrite) contains receptors.
Many (not all) dendrites are covered
in spines.
3D reconstruction of dendritic spines
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