The fibers coming to the 
cortex from the lateral 
geniculate body enter from the 
white matter. Running 
diagonally, most make their 
way up to layer 4C, branching 
again and again, and finally 
terminate by making synapses 
with the stellate cells that 
populate that layer. Axons 
originating from the two 
ventral (magnocellular) 
geniculate layers end in the 
upper half of 4C, called 4Ca; 
those from the four dorsal 
(parvocellular) geniculate 
layers end in the lower half of 
4C (4Cß). As you can see from the 
diagram to the left, these 
subdivisions of layer 4C have 
different projections to the 
upper layers: 4Ca sends its 
output to 4B; 4Cß, to the deepest 
part of 3. And those layers in 
turn differ in their projections. 
Seeing these differences in the 
pathways stemming from the 
two sets of geniculate layers is 
one of many reasons to think 
that they represent two 
different systems. Most 
pyramidal cells in layers 2, 3, 
4A, 5, and 6 send axons out of 
the cortex, but side-branches, 
called "collaterals", of these 
same descending axons connect 
locally and help to distribute 
the information through the 
full cortical thickness.