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


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

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

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

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

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

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

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)

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
  • 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.

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

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

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

(1744 - 1829) selection
A long-standing debate
  • Instructive versus selective change and
  • 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

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,
  • In particular, by the appearance of resistant
    microbial strains
  • A debate about what?

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)

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
  • 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
  • Selection acts post hoc and adaptation is a
    result of it

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
  • Principles and parameters (ever since the late
  • Parameter-based language acquisition

No learning
  • Rather the fixation of a handful of linguistic
  • Each having only two possible values
  • or -
  • A cascade of switches

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Mark Baker 2001, 2003
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

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
  • If the selectivists are right, you get a
    distribution with an abnormally high variance
  • All (or most) of the descendants of a mutant are
  • 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

A technical challenge
  • In order to ascertain the existence of resistant
  • 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.

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.
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)
  • 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

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
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

Next classic experiment
  • Preceded, over many years, by a puzzle (enzymatic
  • 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
  • (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?

Jacques Monod and the double growth (diauxia)
Log n
Glucose Xylose
Jacques Monod and the double growth (diauxia)
Log n
Glucose Xylose
Actually observed
Monods original (non-logarithmic) graphs
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

Monods and Jacobs explanation
  • The regulating mechanism and the final result
    have been associated and fine-tuned by natural
  • (the inductor is the very metabolite that the
    enzyme - expressed by the activated gene -
  • 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
In the presence of lactose repressor cannot bind
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

The case of antibodies
  • Selectivism, then 50 years of instructivism
  • Then, finally, selectivism

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
  • This theory was based on an understanding of the
    way in which a cell was thought to absorb and
    assimilate nutrients.

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
  • 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.

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
  • Antibodies pre-exist.

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.

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

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
  • Antibody formation takes place by the assembly of
    the antibody molecule on the antigen
    (instructivist model).

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
  • 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.

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.

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

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.
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.

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.

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)

Chomskys Review of Skinners Verbal Behavior
  • 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

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

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.

Another window of opportunitySelective visual
  • 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
  • The crucial importance of critical periods.
  • The crucial importance of competitive mechanisms

In essence a whole new paradigm
  • The specificity and fine-graininess of the innate
  • (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

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

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.

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.

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.
Optic nerve
Optic chasm
Optic tract
Lateral geniculate body
Primary visual cortex
Area 17
Area V1
(Drawing by Jeff Stripling)
Striate cortex
Area 17
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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
  • If, instead, we proceed horizontally (parallel
    to the surface of the cortex), we encounter
    groups of cells that have different
  • With abrupt transitions in functional properties
    which separate one column from the next.
  • See http//

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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
  • 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.

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.

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

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

A subtle concept The receptive field
  • http//
  • 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,
  • 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

See David Hubels online book Eye, Brain and
Vision http//
No stimulus
No stimulus
On-center retinal ganglion cell
Off-center retinal ganglion cell
Stephen Kuffler (Johns Hopkins, ever since 1952)
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.
Responses to a long, narrow slit of light
Orientation is crucial
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

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

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

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.

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

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//

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)

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.

  • 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.

Projections from one eye only (the ipsilateral
one) in the adult macaques striate cortex
From Wiesels Nobel Lecture
1,256 cells
Monocularly deprived at 2 weeks for 18 months
100 cells
Ocular dominance histograms (Rhesus macaque)
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
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.
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

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
  • 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

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.

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
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