Netherlands Graduate School of Linguistics LOT Summer School 2006 Issues in the biology and evolution of language

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Netherlands Graduate School of Linguistics LOT
Summer School 2006Issues in the biology and
evolution of language

• Massimo Piattelli-Palmarini
• University of Arizona
• Session 1 (June 12)
• The birth of a paradigm Innatism versus
  selectivism

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Plan of this course

• Today (Monday) The birth of selectivism and the
  idea of parameters
• Tuesday Towards a genetics of language
• Wednesday Loss of speech
• Thursday The return of the laws of form
• Friday Contemporary biology and the minimalist
  program

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Little guide to the readings

• General position papers on biolinguistics
• Chomskys Three factors
• My paper with Cedric Boeckx
• Freidin and Vergnaud
• Tutorials
• Boeckx Chapter 5 on minimalism
• My handout on the Hauser, Chomsky and Fitch
  versus Pinker and Jackendoff on evolution
• Christiansen and Kirby on language evolution
• NEW Simon Fisher The tangled web in Cognition
  June 6, 06

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Little guide to the readings (2)

• Representative pieces
• Turing on morphogenesis
• Davidson and Erwin on Gene Networks
• Hill and Walsh on brain evolution
• Marcus and Fisher (on FOXP2)
• Gibbs on epigenetics
• Punctual papers
• Somerville et al. on Williams syndrome
• Fisher on genes and language
• Scharf and White on Foxp2 in birds
• Uriagereka and me on the immune syntax
  (unreadable)

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Some caveats

• The biology of language is a huge field
• 750 papers just on brain imaging and language
• About 150 references (papers and books) on the
  evolution of language, just in the last 10 years
  or so
• About 25 genes (tentatively) identified already
  as being language-related
• Many other fields are relevant (molecular
  genetics, evo-devo, neuroscience of cognition,
  various pathologies, comparative cognitive
  ethology etc.)
• Not to mention, of course, linguistics, language
  acquisition and psycholinguistics

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Some caveats

• Our strategy here
• Explore with a critical eye the possibility of
  a biology of language
• Its logic and its possible import
• Privileging what we know (rather than what we
  would like to know, but we dont)
• Concentrating on the strong points
• Singling out the best cases (breakthroughs)
• And plausible avenues of future development
• With (yes!) some fine details that may, at
  first blush, seem of scant interest to linguists
• But they are not (I hope I will persuade you that
  they are really very interesting)

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Three factors in language design

• (1) genetic endowment, which sets limits on the
  attainable languages, thereby making language
  acquisition possible
• (2) external data, converted to the experience
  that selects one or another language within a
  narrow range
• (3) principles not specific to FL.
• Some of the third factor principles have the
  flavor of the constraints that enter into all
  facets of growth and evolution, and that are now
  being explored intensively in the evo-devo
  revolution.
• There are other third factor elements as well,
  among them properties of the human brain that
  determine what cognitive systems can exist. It
  also might turn out that general cognitive
  principles that enter into language acquisition
  pose conditions on FL design.

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Two varieties of pessimism

• Max Planck A new scientific truth does not
  triumph by convincing its opponents and making
  them see the light, but rather because its
  opponents eventually die, and a new generation
  grow up that is familiar with it.
• Noam Chomsky New ideas circulate only because,
  eventually, professors are embarrassed by their
  students for confessing they do not know about
  them.

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The innatist-selectivist explanatory strategy

• Enters linguistics via the Poverty of the
  Stimulus (POS)
• Explicit references (in earlier work by Chomsky)
  to Luria and Delbruck, to Hubel and Wiesel and to
  Monod and Jacob.
• In continuity with the powerfully emerging trend
  in molecular biology
• Later reinforced by Fodors modularity
• By data on language acquisition
• And by the principles-and-parameters framework

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Charles Darwin
Jean-Baptiste de Lamarck (1809 -1882)

(1744 - 1829) selection
instruction
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A long-standing debate

• Instructive versus selective change and
  adaptation
• Revamped in immunology (around 1890)
• Revamped in microbiology (Pasteur and Koch, from
  1880 onwards)
• Kochs postulate one disease one microbial
  agent (cholera, typhus, tuberculosis etc.)
• Doubts that bacteria could have a genetics
  until about 1935
• Frederick Griffith (1928) the transforming
  agent of pneumococcus from harmless to pathogenic

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A long-standing debate (continued)

• Avery, McLeod and McCarty (1944) the
  transforming agent is DNA
• Quite a shock to everyone (Nobel Prize 1983)
• Further revamped by the discovery of the healing
  power of antibiotics in the late Thirties and
  Forties (penicillin, streptomycin,
  chloramphenicol)
• In particular, by the appearance of resistant
  microbial strains
• A debate about what?

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Two positions The first

• The inductivists (Felix DHérelle et al.)
  Adaptive mutations are induced by the external
  agent (temperature, antibiotics, viruses,
  metabolites etc.)
• There are directed adaptive heritable changes
  (induced adaptations)
• The reference conceptual model spontaneous
  radioactive decay
• (The probability of decaying is constant across
  all atoms of a given isotope of that element)
• And catalysis (the dominant conceptual model)

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Two positions The second

• The selectivists (A. Gratia, F. M. Burnet et
  al.) Mutations are spontaneous, with a stable
  fixed average probability of occurrence (about
  10-8 per locus per generation)
• BUT
• They occur independently of, in the absence of,
  and prior to, any exposure to the environmental
  factor.
• No directionality.
• At the 3rd Congress of Microbiology in New York,
  in 1939, Andre Gratia declared "Adaptation by
  passive selection of pre-existing variants is the
  only fact to be proven beyond any doubt" (GRATIA
  1939)
• Selection acts post hoc and adaptation is a
  result of it

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Why do we care?

• Reference to these phenomena, and to selectivist
  explanations, is ubiquitous in Chomskys work
  (see his debate with Piaget)
• Luria and Chomsky and Eric Lenneberg at MIT
  created a bio-linguistics group meeting regularly
• The 1974 meeting at Endicott House
• Fodors innatism and the pre-existence of all
  concepts
• Principles and parameters (ever since the late
  Seventies)
• Parameter-based language acquisition

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No learning

• Rather the fixation of a handful of linguistic
  parameters
• Each having only two possible values
• or -
• A cascade of switches

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Mark Baker 2001, 2003
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A simple knockdown experiment

• Salvador E. Luria and Max Delbrück (1943)
  Mutation of bacteria from virus sensitivity to
  virus resistance, Genetics, Vol. 28, pp 491-511
• Nobel Prize in 1969 with Alfred D. Hershey
• Hall of fame of elegant experiments in biology
• Inspiration from a slot-machine in a Country Club
  in Bloomington Indiana
• The very idea Grow different cultures of
  bacteria sensitive to a virus (a phage)
• Make successive dilutions of samples from the
  various cultures (successive generations)
• Add the virus, then see how many resistant
  colonies you obtain

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A simple knockdown experiment

• If the inductivists are right, then
• You get an average constant percentage of
  resistant mutants at each generation
• If and only if, they have been exposed to the
  virus.
• If the selectivists are right, you get a
  distribution with an abnormally high variance
• All (or most) of the descendants of a mutant are
  resistant
• All (or most) of the descendants of a sensitive
  wild type are wiped out
• The presence of the virus allows us to make a
  selection, but it is not the inducing agent

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A technical challenge

• In order to ascertain the existence of resistant
  mutants
• You have to add the virus to the culture
• But then its hard to decide whether the mutants
  pre-existed or are induced by the virus
• Lurias and Delbrücks solution
• Fluctuations across generations.

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The Luria-Delbrück dilution experiment
Bacteria sensitive to the virus (a bacteriophage)
in black. Resistant mutants in red. Culture 1
harbors a 3rd generation mutant. Culture 3
harbors a 1st generation mutant. The probability
of observing mutants varies very strongly. In
fact, it is 1 or 0, depending on whether the
ancestor is or is not a mutant.
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The Luria-Delbrück dilution experiment
Had the mutation been induced by the exposure,
we would Expect a uniform probability of finding
mutant colonies (an average constant fraction of
all later cultures would be mutants)
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Conclusion

• We consider the above results as proof that in
  our case the resistance to virus is due to a
  heritable change of the bacterial cell which
  occurs independently of the action of the virus.
  (emphasis added)
• Do we need successive dilutions?
• Not necessarily
• Same results with a different technique Replica
  Plating

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Replica plating (Joshua and Esther Lederberg 1952)
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The procedure at no time exposes the indirectly
selected populations to the specific agent
streptomycin. These observations, therefore,
are cited as confirmation of previous evidence
for the participation of spontaneous mutation and
population selection in the heritable adaptation
of bacteria to new agents. (emphasis
added) Joshua and Esther Lederberg (then at
Madison Wisconsin) Journal of Bacteriology, 1952
Joshua Lederberg, Nobel Prize 1959 for studies
on genetic recombination and organization of the
genetic material in bacteria
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1st important lesson

• The selective agent does not induce the mutation
• It selects pre-existing mutants
• Specific mutants pre-exist, regardless of all
  encounters with the selective agent

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Next classic experiment

• Preceded, over many years, by a puzzle (enzymatic
  adaptation)
• Something you expected to happen but doesnt.
• Imagine the following cases
• (1) A new kind of combustion engine
• Outputs 200 HPs when burning fuel A
• Outputs 300 HPs when burning fuel B
• What do you expect with a mixture of the two
  fuels?
• (2) Most patients recover in 30 days under
  treatment with antibiotic A
• Most patients recover in 60 days under treatment
  with antibiotic B
• What do you expect with a mixed treatment?

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Jacques Monod and the double growth (diauxia)
(1940)
2
Glucose
1
1
Xylose
t
t
Log n
Glucose Xylose
Expected
t
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Jacques Monod and the double growth (diauxia)
(1940)
2
Glucose
1
1
Xylose
t
t
Log n
Glucose Xylose
Actually observed
t
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Monods original (non-logarithmic) graphs
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In Monods doctoral dissertation (1940)

• Microbiology will not make much progress until
  we have solved this puzzle.
• It took 20 years to solve it
• Genetic regulation as a switching process
• (not a catalytic one)
• There are DNA sequences (genes) whose exclusive
  function is the activation-inactivation of
  adjacent genes.
• Nobel Prize with François Jacob and André Lwoff
  in 1965

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Monods and Jacobs explanation

• The regulating mechanism and the final result
  have been associated and fine-tuned by natural
  selection
• (the inductor is the very metabolite that the
  enzyme - expressed by the activated gene -
  digests)
• But the process is totally mechanical
• The regulator and its gene can be separately
  disassembled and re-assembled at leisure

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In the absence of lactose repressor blocks
promoter
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In the presence of lactose repressor cannot bind
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Central points

• Seeing clearly that a puzzle in a class of
  phenomena stonewalls the discipline as a whole
• Even in the absence of the faintest idea on how
  to solve the puzzle
• Seeing clearly that the extant conceptualizations
  (catalysis) cannot begin to solve the puzzle
• An educated guess that the solution of the puzzle
  will reverberate much beyond that class of
  phenomena

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The case of antibodies

• Selectivism, then 50 years of instructivism
• Then, finally, selectivism

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How everything began Paul Ehrlich

• The hypothesis Ehrlich developed to explain
  immunological phenomena was the side-chain
  theory, which described how antibodies - the
  protective proteins produced by the immune system
  - are formed and how they react with other
  substances.
• This theory was based on an understanding of the
  way in which a cell was thought to absorb and
  assimilate nutrients.

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Ehrlichs side-chain theory ofantibody production

• Each cell has on its surface a series of side
  chains, or receptors, that function by attaching
  to certain food molecules.
• While each side chain interacts with a specific
  nutrient - in the same manner as a key fits into
  a lock - it can also interact with
  disease-causing toxins produced by an infectious
  agent.
• When a toxin binds to a side chain, the
  interaction is irreversible and blocks subsequent
  binding and uptake of nutrients.
• The body then tries to overwhelm the obstruction
  by producing a great number of replacement side
  chains so many that they cannot fit on the
  surface of the cell and instead are secreted into
  the circulation.

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Ehrlichs side-chain theory ofantibody production

• According to Ehrlich's theory, the circulating
  side chains are the antibodies, which are all
  gauged to and able to neutralize the
  disease-causing toxin and then remain in the
  circulation, thus immunizing the individual
  against subsequent invasions by the infectious
  agent.
• Antibodies pre-exist.

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Karl Landsteiner and the dawn of biochemistry

• Small organic molecules of simple structure, such
  as phenyl arsonates and nitrophenyls, are not
  natural danger signals, and do not provoke
  antibodies when injected by themselves.
• However, antibodies can be raised against them if
  the molecule is attached covalently, by simple
  chemical reactions, to a protein carrier.
• Such small molecules were termed haptens (from
  the Greek haptein, to fasten) by the immunologist
  Karl Landsteiner, who first studied them in the
  early 1900s.

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Karl Landsteiner and the dawn of biochemistry

• Landsteiner found that animals immunized with a
  hapten-carrier conjugate respond by producing
  distinct sets of antibodies.
• No lock-and-key, but a more or less good fit.
• Antibodies drape themselves over the charge
  outline of their target antigen (instructivist
  model).

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Felix Haurowitz and the Template Theory of
Antibody Formation.Selectivism is unvorstellbar

• Haurowitz and Landsteiner collaborated to define
  the chemical nature of antibodies.
• "I concluded that the antibody must be serum
  globulin and suggested therefore that the antigen
  interferes with the process of globulin
  biosynthesis in such a way that globulins
  complementarily adjusted to the antigen are
  formed."
• Antibody formation takes place by the assembly of
  the antibody molecule on the antigen
  (instructivist model).

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The 1984 Nobel Prize in Physiology or Medicine
Niels Jerne

• Niels Jernes natural selection theory for the
  immune system was published in 1955 (!).
• Lederberg and Nossall one lymphocyte clone one
  antibody
• Jerne proposed that the capacity of the immune
  system to recognize millions of foreign molecules
  was predetermined, already existing in the body
  when the very first contact with a foreign
  structure was made. What then happened was merely
  a selection amongst the naturally occurring
  antibody population resulting in an increase in
  production of exactly those antibodies which
  happened to have a good fit for the structure.

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The 1984 Nobel Prize in Physiology or Medicine
Niels Jerne

• Jerne's theory stood in great contrast to
  prevailing theories at that time (the
  unimaginable wastefulness of selection), but was
  rapidly confirmed and extended.
• Natural selection applies to the cells of the
  immune system. Those cells which happen to have
  received the property to produce a wanted
  antibody type will upon vaccination be rewarded
  with proliferative capacity and survival.

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The adaptive immune response

• The molecules of adaptive immunity (e.g.,
  antibodies)
• Are generated by random DNA rearrangements
• Pre-exist to the encounter with danger signals
  (innate)
• Are selected by specific stimuli
• Repertoire is virtually unlimited (3D recognition
  of molecular shapes)

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Grammar is a science that is more than 2000 years
old, whereas immunology has become a respectable
part of biology only during the past hundred
years. Though both sciences still face
exasperating problems, this lecture attempts to
establish an analogy between linguistics and
immunology, between the descriptions of language
and of the immune system.
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An immunologist quotes a linguist

• At this point, I (Jerne) shall make a quotation
  from Noam Chomsky concerning linguistics
• The central fact to which any significant
  linguistic theory must address itself is this a
  mature speaker can produce a new sentence of his
  language on the appropriate occasion, and other
  speakers can understand it immediately, though it
  is equally new to them Grammar is a device that
  specifies the infinite set of well-formed
  sentences and assigns to each of these one or
  more structural descriptions. Perhaps we should
  call such a device a generative grammar which
  should, ideally, contain a central syntactic
  component, a phonological component and a
  semantic component.

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Jernes conclusion

• The inheritable deep structure of the immune
  system is now known certain chromosomes of all
  vertebrate animals contain DNA segments which
  encode the variable regions of antibody
  polypeptides. Furthermore, experiments in recent
  years have demonstrated the generative capacities
  of this innate system.

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A remarkable insight

• It seems a miracle that young children easily
  learn the language of any environment into which
  they were born. The generative approach to
  grammar, pioneered by Chomsky, argues that this
  is only explicable if certain deep, universal
  features of this competence are innate
  characteristics of the human brain. Biologically
  speaking, this hypothesis of an inheritable
  capability to learn any language means that it
  must somehow be encoded in the DNA of our
  chromosomes. Should this hypothesis one day be
  verified, then linguistics would become a branch
  of biology. (emphasis added)

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Chomskys Review of Skinners Verbal Behavior
(1959)

• The magnitude of the failure of this the
  behaviorists attempt to account for verbal
  behavior serves as a kind of measure of the
  importance of the factors omitted from
  consideration, and an indication of how little is
  really known about this remarkably complex
  phenomenon.

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A Review of Skinners Verbal Behavior (1959)

• Study of the actual observed ability of a
  speaker to distinguish sentences from
  non-sentences, detect ambiguities, etc.,
  apparently forces us to the conclusion that this
  grammar is of an extremely complex and abstract
  character, and that the young child has succeeded
  in carrying out what from the formal point of
  view, at least, seems to be a remarkable type of
  theory construction. Furthermore, this task is
  accomplished in an astonishingly short time, to a
  large extent independently of intelligence, and
  in a comparable way by all children. Any theory
  of learning must cope with these facts. (my
  emphasis)

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Jerry Fodor in the debate with Piaget (1976)

• there must be some notion of learning that is
  so incredibly different from the one we have
  imagined that we dont even know what it would be
  like, as things now stand.

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Another window of opportunitySelective visual
deprivation

• Extreme specificity of the sensitivity of
  individual neurons
• Modularity of the organization of the primary
  visual cortex
• Strong innate components
• The selective (not instructive) nature of the
  visual inputs
• The effects of selective deprivation (shift of
  allegiance)
• The crucial importance of critical periods.
• The crucial importance of competitive mechanisms

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In essence a whole new paradigm

• The specificity and fine-graininess of the innate
  endowment
• (pre-wired selective sensitivity to shapes, modes
  of motion, edges, contrasts, etc.)
• Strong modularity
• The role of specific data (from experience) as
  selectors (activators / suppressors)
• The crucial role of critical periods
• The crucial role of competition mechanisms
  (winner-take-all)

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Our two protagonists
David Hubel
Torsten Wiesel
At Johns Hopkins and then at Harvard 1959-1962
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Our two protagonists
David Hubel
Torsten Wiesel
Nobel Prize in 1981
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The role of experience

• From their Nobel lectures
• Innate mechanisms endow the visual system with
  highly specific connections, but visual
  experience early in life is necessary for their
  maintenance and full development.
• Deprivation experiments demonstrate that neural
  connections can be modulated by environmental
  influences during a critical period of postnatal
  development.

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The role of experience (continuation)

• Such sensitivity of the nervous system to the
  effects of experience may represent the
  fundamental mechanism by which the organism
  adapts to its environment during the period of
  growth and development.

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A central reflection, an afterthought

• Visual experience seems to have the power of
  validating or vetoing not only the outcomes of
  the process of differentiation but the process
  itself. (my emphasis)
• Wiesel, T.N. 1982 Postnatal development of the
  visual cortex and the influence of environment.
  Nature, 299, 583-591.

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Blakemore, C., and Cooper, G. F. (1970).
Development of the brain depends on the visual
environment. Nature , 228477-478.
The result is that the vertical cells multiply,
while the horizontal cells shrink
and degenerate. Neither eye was ever closed.
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Optic nerve
Optic chasm
Optic tract
Lateral geniculate body
Primary visual cortex
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Area 17
Area V1
(Drawing by Jeff Stripling)
Striate cortex
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Area 17
http//webvision.med.utah.edu/imageswv/capas-corte
x.jpg
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The columnar organization of the cortex

• In the years 1955-1959 Vernon B. Mountcastle (at
  Johns Hopkins University) discovered the columnar
  organization of the cortex
• Basically, this means that, as we proceed
  vertically, from the outside inwards,
• we encounter groups of cells (of about 100 cells
  each) that are very similar in their
  specialization (they are sensitive to the same
  stimuli)
• If, instead, we proceed horizontally (parallel
  to the surface of the cortex), we encounter
  groups of cells that have different
  specializations.
• With abrupt transitions in functional properties
  which separate one column from the next.
• See http//cercor.oupjournals.org/cgi/content/full
  /13/1/2

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The meaning of a column

• In Hubels words
• A column a little machine that takes care of
  contours in a certain orientation in a certain
  part of the visual field.
• If the cells of one set are to be interconnected,
  and to some extent isolated from neighboring
  sets, it makes obvious sense to gather them
  together.
• The function of the visual cortex is the
  transformation of information from circularly
  symmetric form to orientation-specific form, and
  the stepwise increase in complexity.

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Binocular cells

• A high proportion of cells in the primary visual
  (striate) cortex receive inputs from both eyes.
• BUT
• In the lateral geniculate body, cells receive
  input from one eye only.
• Hubel and Wiesel discovered that there is a
  striking similarity of the corresponding cells
  receptive fields in the two eyes, in size,
  complexity, orientation and position.
• Presumably this forms the basis of the fusion of
  the images in the two eyes.

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A wonderful online treatise on eye and vision,
with great images

• http//webvision.med.utah.edu/index.html

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The first processing station

• The retinal ganglion cells are the output of
  the retina
• They act largely independently one from the other
  to encode information
• see Niremberg S. et al (2001) Nature Vol. 411,
  pp. 698-701
• They gather and integrate impulses from several
  cells in the retina
• Haldan Keffer Hartline (Nobel with Ragnar Granit
  and George Wald in 1967) discovered in 1935 that
  there are basically three kinds of such cells
  The ON, the OFF and the ON-OFF ganglion cells

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A subtle concept The receptive field

• http//psych.hanover.edu/Krantz/receptive/
• The region of the retina within which a local
  change of brightness would cause the ganglion
  cell to discharge (Hartline, 1935-38)
• The interactive annulus (center and ring) that
  causes a ganglion cell to discharge (Kuffler,
  1953)
• Includes the structure of the effective stimulus
  (Hubel and Wiesel, 1956)
• area of the visual field in which stimulation
  leads to response of a particular sensory neuron
  (Levine and Shefner, 1991)
• Notice The definition went from the retina to
  the outside world

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See David Hubels online book Eye, Brain and
Vision http//neuro.med.harvard.edu/site/dh/bconte
x.htm
No stimulus
No stimulus
On-center retinal ganglion cell
Off-center retinal ganglion cell
Stephen Kuffler (Johns Hopkins, ever since 1952)
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This cell not only responds exclusively to a
moving slit in an eleven o'clock orientation but
also responds to movement right and up, but
hardly at all to movement left and down.
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Responses to a long, narrow slit of light
Orientation is crucial
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How narrow is the optimum angle?

• Typically its 10-20 degrees
• Notice that the degree between two successive
  hours on a clock dial is 30 degrees

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A typical vertical cell
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A typical (vertically) directionally sensitive
complex cell, more sensitive to the top-down than
to the bottom-up displacement
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A remarkable fact (Pasko Rakic 1972)

• By the 26th gestational week the human neocortex
  is already composed of a large number of
  minicolumns in parallel vertical arrays.
• This remarkable regularity is revealed in
  histological sections closely aligned with the
  vertical axes of minicolumns.
• At least at the level of the cortex, modularity
  is quite precocious.
• Columns vary between 300 and 500 µm in transverse
  diameter, and do not differ significantly in size
  between brains that vary in size over three
  orders of magnitude (Bugbee and Goldman-Rakic,
  1983)

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Species-specificity of the critical period

• The length of the critical period varies between
  species.
• In cats it is 3 to 4 months
• And from clinical observations in humans (in
  ophthalmology clinics) it may extend up to 5 - 10
  years,
• though the susceptibility to deprivation appears
  to be most pronounced during the first year and
  declines with age.

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The organization

• Cells of different complexities, whose receptive
  fields are in the same part of the visual field
  and which have the same optimal orientation, are
  likely to be interconnected, whereas cells with
  different optimal orientations are far less
  likely to be interconnected.

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S. M. Kosslyn, A. Pascual-Leone, et al Science
Vol 284, pp. 167-170,1999
88
References

• Pathways of the Brain, chapters 16-17 and Vernon
  Mountcastle Perceptual Neuroscience The Cerebral
  Cortex, Harvard University Press, 1998. See also
  Yves Burnod, An Adaptive Neural Nework The
  Cerebral Cortex (1990)

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The forming of maps and associations

• Cortical columns in sensory areas (auditory,
  visual, somatosensory) form maps.
• Regions of cortex adjacent to these maps are
  associative, with the associations becoming
  progressively higher level and more abstract with
  greater distance from the sensory map.
• For instance, the intensities of different
  frequencies of sound waves are mapped on the
  planum temporale,
• while cortical areas in more inferior areas of
  the temporal lobe process higher level
  information, starting with sounds and moving to
  word concepts.
• http//www.ruf.rice.edu/lngbrain/Farh/cc.html

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The famous deprivation experiments

• In an animal that has undergone monocular
  deprivation, the geniculate terminals with input
  from the non-deprived eye take over much of the
  space that would normally have been occupied by
  terminals from the deprived eye.
• The deprived eye input has shrunken down to
  occupy the small strips lying between the
  terminals of the non-deprived eye input.
• Tangential electrode penetrations through
  cortical layers reveal long expanses of cells
  driven by the non-deprived eye interrupted by
  small patches of cells that are either
  unresponsive or driven by the deprived eye.
• From the Nobel lectures (emphasis added)

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Shift of allegiance, not un-responsiveness

• Cells at later stages have shifted their
  allegiance from the deprived to the non-deprived
  eye, rather than becoming unresponsive. (my -
  MPP - emphasis)
• This conclusion is supported by the
  physiological findings that the large majority of
  cells in superficial and deep layers respond only
  to the stimulation of the normal eye.

92
Innateness

• It still seems remarkable that a cell should not
  only be wired with the precision necessary to
  produce complex or hyper-complex properties, but
  should have a duplicate set of such connections,
  one from each eye.
• That this is hard wired at birth forms some of
  the material of Torsten Wiesels lecture.
• In vertical penetrations the preference remains
  the same all the way through the cortex.

93
Projections from one eye only (the ipsilateral
one) in the adult macaques striate cortex
94
From Wiesels Nobel Lecture
1,256 cells
Monocularly deprived at 2 weeks for 18 months
100 cells
ipsilateral
Ocular dominance histograms (Rhesus macaque)
95
Ocular dominance histograms
At 10 weeks for 4 months
Right eye closed at 2 weeks for 18 months
At 1 year for 1 year
At 6 years for 1and 1/2 years
96
The sooner, the worse, and no recovery
Adult monkey whose right eye had been closed
from 21 to 30 days of age. Tested after 4 years
of normal vision
20-day-old monkey whose right eye had been
closed since 8 days of age.
97
A more recent validation

• Innate mechanisms endow the visual system with
  highly specific connections, although the
  specificity is initially blurred by a high degree
  of exuberant growth.
• Pascal D. Zufferey, Fuzi Jin, Hiroyuki Nakamura,
  Laurent Tettoni and Giorgio M. Innocenti European
  Journal of Neuroscience Volume 1, Page 2669  -
  August 1999

98
A later generalization

• The connective organization of an evolving
  neuronal network is related to the effects of the
  environment on this organization
• by stabilization or degeneration of labile
  synapses associated with functioning.
• Learning, or the acquisition of an associative
  property, is related to a characteristic
  variability of the connective organization
• the interaction of the environment with the
  genetic program is printed as a particular
  pattern of such organization through neuronal
  functioning.
• A Theory of the Epigenesis of Neuronal Networks
  by Selective Stabilization of Synapses, by
  Jean-Pierre Changeux, Philippe Courrege and
  Antoine Danchin PNAS (1973) vol. 70 pp 2974-2978

99
Another Nobel Prizewinner(but for a very
different kind of work)

• The theory of neuronal group selection (Neural
  Darwinism) by Gerald Edelman (Basic Books, 1987)
• Focus on perceptual categorization as it relates
  to memory and learning.
• He proposes that these functions could be
  understood in terms of "neural Darwinism"
• the idea that higher brain functions are mediated
  by developmental and somatic selection upon
  anatomical and functional variance occurring in
  each individual animal.

100
Overflow of the paradigm onto linguistics

• Essentially, detailed in my 1989 Cognition paper
  Evolution, selection and cognition From
  learning to parameter-setting in biology and in
  the study of language
• In two parts, for electronic viability
• Downloadable in pdf from my web-page