In a very pretty extension of 
the same idea, Roger Tootell, in 
Russel De Valois's laboratory at 
Berkeley, had an animal look 
with one eye at a large pattern 
of concentric circles and rays, 
shown in the top image of the 
figure to the left. 

In this experiment by Roger 
Tootell, the target-shaped 
stimulus with radial lines was 
centered on an anesthetized 
macaque monkey's right visual 
field for 45 minutes after 
injection with radioactive 2-
deoxyglucose. One eye was held 
closed. The lower picture shows 
the labeling in the striate 
cortex of the left hemisphere. 
This autoradiograph shows a 
section parallel to the surface; 
the cortex was flattened and 
frozen before sectioning. The 
roughly vertical lines of label 
represent the (semi)circular 
stimulus lines; the horizontal 
lines of label represent the 
radial lines in the right visual 
field. The hatching within each 
line of label is caused by only 
one eye having been stimulated 
and represents ocular-
dominance columns.

The resulting pattern on the 
cortex contains the circles and 
rays, distorted just as expected 
by the variations in 
magnification (the distance on 
the cortex corresponding to 1 
degree of visual field), a 
phenomenon related to the 
change in visual acuity 
between the fovea and 
periphery of the eye. Over and 
above that, each circle or ray is 
broken up by the fine ocular-
dominance stripes. Stimulating 
both eyes would have resulted 
in continuous bands. Seldom 
can we illustrate so many 
separate facts so neatly, all in a 
single experiment.

    Cats, several kinds of 
monkeys, chimpanzees, and 
man all possess ocular-
dominance columns. The 
columns are absent in rodents 
and tree shrews; and although 
hints of their presence can be 
detected physiologically in the 
squirrel monkey, a new world 
monkey, present anatomical 
methods do not reveal the 
columns. At present we don't 
know what purpose this highly 
patterned segregation of eye 
influence serves, but one guess 
is that it has something to do 
with stereopsis (see Chapter 7).

    Subdivisions of the cortex by 
specialization in cell function 
have been found in many 
regions besides the striate 
cortex. They were first seen in 
the somato-sensory cortex by 
Vernon Mountcastle in the mid-
1950s, in what was surely the 
most important set of 
observations on cortex since 
localization of function was 
first discovered. The 
somatosensory is to touch, 
pressure, and joint position 
what the striate cortex is to 
vision. Mountcastle showed 
that this cortex is similarly 
subdivided vertically into 
regions in which cells are 
sensitive to touch and regions 
in which cells respond to 
bending of joints or applying 
deep pressure to a limb. Like 
ocular-dominance columns, 
the regions are about half a 
millimeter across, but whether 
they form stripes, a 
checkerboard, or an ocean-
and-islands pattern is still not 
clear. The term column was 
coined by Mountcastle, so one 
can probably assume that he 
had a pillarlike structure in 
mind. We now know that the 
word slab would be more 
suitable for the visual cortex. 
Terminology is hard to change, 
however, and it seems best to 
stick to the well-known term, 
despite its shortcomings. Today 
we speak of columnar 
subdivisions when some cell 
attribute remains constant 
from surface to white matter 
and varies in records taken 
parallel to the surface. For 
reasons that will become clear 
in the next chapter, we usually 
restrict the concept to exclude 
the topographic representation, 
that is, position of receptive 
fields on the retina or position 
on the body.