Model of Retinogeniculate Development: Dissertation Available Online

[Gary Haith]

MODELING ACTIVITY-DEPENDENT DEVELOPMENT IN THE RETINOGENICULATE
PROJECTION can be downloaded at:

(post-script document):
http://ic-www.arc.nasa.gov/people/haith/diss.ps 

(gzipped post-script document):
http://ic-www.arc.nasa.gov/people/haith/diss.ps.gz 

Gary Haith
haith at ptolemy.arc.nasa.gov

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Abstract:
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In higher mammals, the primary visual pathway starts with the
(``retinogeniculate'') projection from the retina to the dorsal
lateral geniculate nucleus (dLGN) of the thalamus, which in turn
projects to visual cortex.  Although the retinal axons initially
innervate the dLGN in a relatively disorganized manner, they are
precisely arranged by maturity.  Some dominant features of this
organization emerge only under the influence of activity, yet these
features are established before eye-opening or photoreceptor function.
The crucial activity is supplied by spontaneous bursts of action
potentials that propagate in waves across the immature retinal
ganglion cell layer that projects to the dLGN.  Under the
influence of retinal activity, the retinal axons segregate into
eye-specific layers, on/off sublayers, and precise retinotopic maps.

This dissertation describes a formal computational framework for
modeling and exploring the activity-dependent development of the
retinogeniculate projection.  The model is the first to support the
development of layers, sublayers, and retinotopy in a unified
framework.  The model is constructed so as to be directly biologically
interpretable and predictive.  It refines based on realistic patterns
of wave activity, retinal axon arbor change, and Hebbian synaptic weight
change.  In addition, the model is relatively tractable to formal
analysis.  This tractability makes the model relatively undemanding to
simulate computationally and provides analytic insight into the
dynamics of the model refinement.  Several experimental predictions
that follow directly from the model are described.