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Fig. 9. How the precision of the collicular map projected on the retina changes
over time for the four cases described in Figs 7, 8. The receptive field
size (blue line) is the mean diameter of the receptive fields of the
collicular cells; the receptive field separation (dashed line) is the mean
distance between receptive field centres from neighbouring collicular cells.
Both measures are expressed as ratios to the mean spacing between neighbouring
retinal cells. Time plotted on a logarithmic scale. (A) The development
of the normal map shown in Fig. 7A. Both size and separation decrease with
time until they are comparable with the average spacing between retinal cells.
(B) The development of the disordered map shown in Fig. 7B. The
receptive field size stays at a high level; initially all receptive field
centres congregate in one small region of the retina before they increase to
give a large field separation. (C) The development of an ordered map
with weak counter-gradients (Fig. 8A). Precision measures evolve as in A.
(D) The development of a distorted map under the influence of strong
counter-gradients (Fig. 8B). The final field size is significantly greater
than in C, with the map being more disordered.
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