The Journal of Neuroscience, September 15, 1999, 19(18):7951-7970
A Neurotrophic Model of the Development of the
Retinogeniculocortical Pathway Induced by Spontaneous Retinal
Waves
Terry
Elliott and
Nigel R.
Shadbolt
Department of Psychology, University of Nottingham, Nottingham, NG7
2RD, United Kingdom
The development of the retinogeniculate pathway or the
geniculocortical pathway, or both, occurs either before birth or before eye opening in many species. It is widely believed that spontaneous retinal activity could drive the segregation of afferents into eye-specific laminae or columns and the refinement of initially diffuse
receptive fields and the emergence of orderly, retinotopic organization. We show that a recent computational model that generates a phenomenologically accurate representation of spontaneous retinal activity can indeed drive afferent segregation and, more particularly, topographic and receptive field refinement in the
retinogeniculocortical system. We use a model of anatomical synaptic
plasticity based on recent data suggesting that afferents might compete
for limited amounts of retrograde neurotrophic factors (NTFs). We find
that afferent segregation and receptive field formation are disrupted in the presence of exogenous NTFs. We thus predict that infusion of
NTFs into the lateral geniculate nucleus should disrupt normal development and that the infusion of such factors into the striate cortex should disrupt receptive field refinement in addition to the
well known disruption of ocular dominance column (ODC) formation. To
demonstrate that the capacity of our model of plasticity to drive
normal development is not restricted just to spontaneous retinal
activity, we also use a coarse representation of visually evoked
activity in some simulations. We find that such simulations can exhibit
the formation of ODCs followed by their disappearance, reminiscent of
the New World marmoset. A decrease in interocular correlations
stabilizes these ODCs. Thus we predict that divergent strabismus should
render marmoset ODCs stable into adulthood.
Key words:
spontaneous retinal activity; neurotrophic interactions; ocular dominance columns; receptive field refinement; neuronal
development; lateral geniculate nucleus; striate cortex; mathematical
models
Copyright © 1999 Society for Neuroscience 0270-6474/99/19187951-20$05.00/0