ocular dominance, input, and language

[Ping Li]

Dear Gary, Brian, and Info-childes,

There are two points that I'd like to make (briefly) in response to Gary's
messages:

(1) The "interactive" brain development view is interesting because for too
long developmental psycholinguists have been led to believe that it is the
neural structure of the brain that dictates language development (ala
Chomskyan LAD/UG and Fodorian modularity) - but now evidence suggests that
the learning environment (e.g., input, or what you call womb-external
experience) can "dictate" or change the neural structure of the brain and
that's interesting. Perhaps many mechanisms that we previously thought to
be innate are actually due to very early interative brain developments on
the basis of experience.

(2) Like Brian, I would question the relevance of ocular dominance and the
like to language development. A nativist proposal in language involves much
more abstract notions than ocular dominance columns, and the question here
is whether things like the UG parameters exist prior to experience (and
that experience helps only to set the parameter values). Perhaps the
parameters are after all established on the basis of experience, and
answers to such questions require the examination of the infant's
"interactive" brain development from 0;0 on (Gary, your 7-month-old infants
already had a lot of womb-external linguistic experiences; see Elman (1999)
"Generalization, rules, and neural networks: A simulation of Marcus et. al"
for a similar point at
http://crl.ucsd.edu/~elman/Papers/MVRVsimulation.html).

Best wishes,

Ping

> >X-Sender: gfm1 at is7.nyu.edu
> >Date: Thu, 02 Dec 1999 21:34:18 -0500
> >To: Brian MacWhinney <macw at cmu.edu>
> >From: Gary Marcus <gary.marcus at nyu.edu>
> >Subject: Re: ocular dominance and input
> >Cc: info-childes at childes.psy.cmu.edu, Ping Li <pli at richmond.edu>
> >Mime-Version: 1.0
> >
> >Dear Brian (cc: Ping, and info-CHILDES),
> >
> >In my view, you are confusing the question of activity-dependence with the
> >question of learning. In my discussion of Hubener and Bonhoeffer (and
> >implicitly Crowley & Katz, Nature Neuroscience, 2, 1125-1130),  I wrote
> >that the "basic structure [of some aspects of V1] seems to be available
> >prior to (womb-external) experience." You seem to challenge my
> >interpretation, by saying that it is open question whether
> >activity-dependence plays an important role in the formation of (the
> >relevant aspects of) V1.  But while I agree that  it is for now unclear
> >whether activity-dependence plays an important role in the formation of
> >(the relevant aspects of) V1, I don't think that lack of clarity has
> >anything to do with my question of womb-external learning. It could well
> >turn out that activity plays an important role; but if the
> >relevant  activity is internally generated (as it would have to be in a
> >darkened womb or in Crowley  and Katz's ferrets, whose retinas were
> >surgically removed), we could not attribute the relevant aspects of
> >development to learning.
> >
> >As Katz put it in earlier paper with Shatz, in which he and Shatz discussed
> >internally-generated waves:
> >
> >>  visual experience alone cannot account for many features of visual
> >> system development. In nonhuman primates, for example, ocular dominance
> >> columns in layer 4 begin to form in utero and are fully formed by birth.
> >> Thus, although visual experience can modify existing columns, initial
> >> formation of the stripes is independent of visual experience. Other
> >> features of cortical functional architecture, such as orientation tuning
> >> and orientation columns, are also present before any visual experience...
> >> [Katz, L.C., & Shatz, C.J. (1996). Synaptic activity and the construction
> >> of cortical circuits. Science, 274, 1133-1138].
> >
> >Now, you may not care about the question of "learning vs. maturation", but
> >I do. For me, it is interesting to ask whether particular aspects of the
> >machinery that supports language and cognition arise prior to experience --
> >I thought that that was how we got into this discussion in the first place.
> >For me, then it is interesting that the ocular dominance columns can
> >develop in a darkened womb or in an emulated ferret; I wrote in because I
> >found Ping's letter (and  Nelson's review) to be unbalanced, emphasizing
> >the role of (womb-external) experience without making it clear that such
> >experience is not always required.
> >
> >I find the question of whether brain development is "interactive" far less
> >interesting, for I honestly don't see how the answer could be no. If the
> >development of the stomach or liver is interactive, surely the development
> >of the brain must be too. Crowely and Katz's work is grist for Nelson's
> >mill because everything is. In mammalian development, practically
> >everything is interactive -- cells always communicate with one another,
> >with any given cell's fate in part dependent on its neighbors. Let us not
> >confuse interactivity with learning, though -- some interactions are a
> >consequence of learning, others not. A more nuanced view is the one
> >championed early on in  Elman, et 's recent book Rethinking Innateness
> >(1996, MIT Press); as they put (page 22; see also their table 1.2, page 23):
> >
> >>the term innate refers to changes that arise of interactions that occur
> >>within the organism itself during ontogeny. That is, interactions between
> >>the genes and their molecular and cellular environments without recourse
> >>to information from outside the organism.
> >
> >Crowely and Katz's work could be taken as showing that the formation of
> >ocular dominance columns is innate in exactly this sense.
> >
> >There's no guarantee of course that the mechanisms that shape the ocular
> >dominance columns in an enucleated ferret have anything to do with the
> >mechanisms that shape the brain circuitry for language or cognition.  But
> >it is important to realize that nature's tool kit includes both mechanisms
> >for sculpting microcircuitry on the basis of experience, and mechanisms for
> >sculpting microcircuitry in the absence of experience.
> >
> >Best,
> >Gary
> >
> >p.s. The network simulations that you mention go towards showing one way in
> >which you could in principle use patterns of neural activity to shape the
> >ocular dominance columns, but they do not prove that such mechanisms are
> >*actually used*. As Hubener and Bonhoeffer noted "Crowely and Katz have now
> >cast doubt on this view" -- in this way, Crowely and Katz's work  serves as
> >a potent reminder that there's more than one way to equip a ferret.
> >
> >