Mathematical Tractability of Neural Nets

[Elizabeth Bates]

AMR's point about the need for collaboration is well taken -- and as
a scientist who is virtually obsessed with collaboration (e.g.
cross-linguistic projects over three continents that we've somehow
managed to keep afloat for 15 years) I would be the last to suggest
that we work in our own gardens for a few more decades.  Indeed, I
think we are in the middle of a particularly promising time for
an interaction between neuroscience and the various subfields
of language research.  A few concrete examples: The WAshington
University work on brain metabolism during lexical processing,
exciting new psycholinguistic research using electrophysiological
indices (a 6-dimensional outcome measure that puts old-fashioned
button-press techniques to shame) by Kutas, van Petten, Neville,
Holcomb, Garnsey and others, new "on-line" studies of aphasia that
are telling us a great deal about real-time processing in aphasic
patients using techniques that were not possible 10 - 15 years ago,
developmental studies of infants with focal brain injury that are
looking PROSPECTIVELY at the process of recovery, for the very
first time -- and this is just a small sample.  The technical
advances are great, and the opportunities are even greater.  I also
believe that connectionism will offer new theoretical and experimental
tools for examining language breakdown in aphasia -- such as the
Hinton/Shallice or McClelland/Seidenberg/Patterson collaborations
that I cited earlier.

In short (and I have gone on too long), my point was really a simple
one: the old view of brain organization for language appears to have
been disconfirmed, quite roundly, and the field of aphasiology is
currently seeking a completely new way of characterizing contrasting
forms of language impairment following focal brain injury.  I was
answering Slehar's proposal that we "follow the neurologists" and
accept the old story (e.g. Broca's area = the grammar center, and so
on).  But I would NEVER want or mean to suggest that we give up!!
Of course language is difficult to study (compared, as Touretzky
points out, with low level vision), but it also has its advantages:
(1) it is the only public form of cognition, out there for all of
us to say, and (2) for that reason language is perhaps the best
understood and most easily measured of all higher cognitive processes.
We do indeed live in interesting times, and I am sure we have some
real breakthroughs ahead of us in a cognitive neuroscience of language.. -liz