A second method for 
demonstrating the columns 
reveals the slabs in their full 
thickness, not just the part in 
layer 4. This is the 2-
deoxyglucose method, invented 
by Louis Sokoloff at the National 
Institutes of Health, Bethesda, 
in 1976. It too depends 
ultimately on the ability of 
radioactive substances to 
darken photographic film. The 
method is based on the fact that 
nerve cells, like most cells in 
the body, consume glucose as 
fuel, and the harder they are 
made to work, the more glucose 
they eat. Accordingly, we might 
imagine injecting radioactive 
glucose into an animal, 
stimulating one eye, say the 
right, with patterns for some 
minutes--long enough for the 
glucose to be taken up by the 
active cells in the brain--and 
then removing the brain and 
slicing it, coating the slices 
with silver emulsion, and 
exposing and developing, as 
before. This idea didn't work 
because glucose is consumed by 
the cells and converted to 
energy and degradation 
products, which quickly leak 
back out into the blood stream. 
To sidestep the leakage, 
Sokoloff's ingenious trick was 
to use the substance 
deoxyglucose, which is close 
enough chemically to glucose to 
fool the cells into taking it up: 
they even begin metabolizing it. 
The process of breakdown goes 
only one step along the usual 
chemical degradation path, 
coming to a halt after the 
deoxyglucose is converted to a 
substance (2-deoxyglucose-6-
phosphate) that can be degraded 
no further. Luckily, this 
substance is fat insoluble and 
can't leak out of the cell; so it 
accumulates to levels at which 
it can be detected in 
autoradiographs. What we 
finally see on the film is a 
picture of the brain regions 
that became most active during 
the stimulation period and took 
up most of this fake food. Had 
the animal been moving its arm 
during that time, the motor arm 
area in the cortex would also 
have lit up. In the case of 
stimulating the right eye, what 
we see are the parts of the 
cortex most strongly activated 
by that stimulus, namely, the 
set of right ocular-dominance 
columns. You see the result in 
the photographs to the left.

Two experiments using 
radioactive deoxyglucose. Top: A 
cross section of the two 
hemispheres through the 
occipital lobes in a control 
animal that had its visual field 
stimulated with both eyes open 
following the intravenous 
injection. Bottom: After 
injection, an animal viewed 
the stimulus with one eye open 
and the other closed. The 
ocular-dominance patterns are 
clearly visible in the cortex. 
This experiment was done by C. 
Kennedy, M. H. Des Rosiers, O. 
Sakurada, M. Shinohara, M. 
Reivich, J. W. Jehle, and L. 
Sokoloff.