The stacked-plate organization 
is preserved in going from 
retina to geniculate, except 
that the fibers from the retinas 
are bundled into a cable and 
splayed out again, in an orderly 
way, at their geniculate 
destination.

    As a whole, the sextuple-
plate structure has just one 
topography. Thus the two left 
half-retinal surfaces project to 
one sextuple plate, the left 
lateral geniculate (see the 
figure at left). Similarly, the 
right half-retinas project to the 
right geniculate. Any single 
point in one layer corresponds 
to a point in the animal's field 
of vision (via one eye or the 
other), and movement along the 
layer implies movement in the 
visual field along some path 
dictated by the visual-field-to-
geniculate map. If we move 
instead in a direction 
perpendicular to the layers--for 
example, along the radial line 
in the figure at the head of the 
section--as the electrode passes 
from one layer to the next, the 
receptive fields stay in the 
same part of the visual field but 
the eyes switch--except, of 
course, where the sequence 
reverses. The half visual field 
maps onto each geniculate six 
times, three for each eye, with 
the maps in precise register.