A complete answer would require a long response, however, the short (flip)
answer is that several theorists early on proposed spike synchrony as a
means of solving "the binding problem". Then, when two research groups in
German showed evoked potential synchrony under suggestive (of binding)
stimulus conditions, we were off and running. It was a short step from
there to the suggestion of several other theorists/philosophers that they
could go whole hog and also solve the problem of visual attention, and (why
not) consciousness at the same time.
Obviously, synchrony induced by the stimulus alone is not sexy enough to be
a basis for such higher mental states, which (by intuition) must somehow be
separate from pure stimulus response (we are free, aren't we?).
A few spurious, opinionated, and no doubt controversial and annoying remarks:
The 'binding problem' is a problem in feedforward nets that comes up when
you try to parse visual signals into objects (i.e. in machine vision) --
the brain is not feedforeward, and therefore I doubt feature binding is a
serious problem at all. (In model-based systems, things are bound to begin
with).
Several authors have pointed out in the past that one has to be careful
interpreting cross correlations. In our own work published with Matt
Wilson ten years ago, we concluded based on a realistic network simulation
constructed to examine the mechanisms likely to underlie the data obtained
in Germany:
"Interpreting phase coherence from correlation functions produced from the
average of many simulation trials pointed out the need to distinguish
average phase effects from instantaneous phase effects. Instantaneous
phase implies that the statistics of the correlation function taken at any
trial are consistent with the statistics of the combined data. Average
phase allows for systematic within-trial and between-trial variability and
is, therefore, a weaker assertion of actual coherence. This distinction is
particularly important for theories which rely on phase encoding of
stimulus information. Analysis of our model results indicates that the
observed phase relationships are an average, rather than an instantaneous
effect."
Two related papers (quote from the first):
Wilson, M.A. and Bower, J.M. 1990 Computer simulation of oscillatory
behavior in cerebral cortical networks. In: Advances in Neural information
processing systems. Vol. 2, D. Touretzky, editor. Morgan Kaufmann, San
Mateo, CA., pp. 84-91.
Wilson, M.A. and Bower, J.M. 1991 A computer simulation of oscillatory
behavior in primary visual cerebral cortex. Neural Computation 3: 498-509.
With respect to stimulus or nonstimulus driven synchrony, I suggest we
consider the somewhat larger question, why, in principle, are synchronous
spikes more important than asynchronous ones to begin with. In other words,
why don't all the spikes code information? The common answer is that two
action potentials arriving at the same time on a postsynaptic cell have an
increased probability of inducing a spike in that neuron. However, this
assumes that neurons are simple integrate and fire devices (with no
dendrites), which ample evidence suggests they are not. (The uncommon
admission is that we have no easy way to think about the later possibility).
Finally, the obsession with synchrony and cross correlations HAS produced
two important advances:
1) it gave neurobiologists a safe stepping stone away from coding
information in neuronal firing rates (safe in the sense that you can easily
explain the idea in a paper in Nature or Science, and no real math is
required).
and 2) many neurobiologists are now turning to multi-single neuron
recording techniques so they too can construct (and overinterprete) cross
correlation histograms.
So there is hope --
>I think we desperately need to find a cure for myopia.
sorry, that will have to wait until we understand consciousness. However,
on that subject, I think we should focus on understanding things we can
define first.
Jim Bower