An outline of functional self-organization in V1:
J.J. Wright1, P.D. Bourke2
synchrony, STLR and Hebb rules.
Cognitive Neurodynamics (Springer), Volume 2, Number 2, pp 147-157, June 2008.
1 Liggins Institute and Department of Psychological Medicine, University
of Auckland, Auckland, New Zealand.
2 WASP, University of Western Australia, Perth, Western Australia, Australia.
A model of self-organization of synapses in the striate cortex is described,
and its functional implications discussed. Principal assumptions are: (a) Covariance of
cell firing declines with distance in cortex (b) covariance of stimulus characteristics
declines with distance in the visual field (c) metabolic rates are approximately uniform
in all small axonal segments. Under these constraints, Hebbian learning implies the a
maximally stable synaptic configuration corresponding to anatomically and
physiologically realistic "local maps", each of macro-columnar size, and each
organized as Möbius projections of a “global map” of retinotopic form. Convergence to
the maximally stable configuration is facilitated by the spatio-temporal learning rule. A
tiling of V1, constructed of approximately mirror-image reflections of each local map
by its neighbours is formed. The model supplements standard concepts of feed-forward
visual processing by introducing a new basis for contextual modulation and neural
network identifications of visual signals, as perturbation of the synaptic configuration
by rapid stimulus transients. On a long time-scale, synaptic development could
overwrite the Möbius configuration, while LTP and LTD could mediate synaptic gain
on intermediate time-scales.