Journal of Neuroscience, Vol 16, 2086-2096, Copyright © 1996 by Society for Neuroscience
Ocular dominance columns in New World monkeys
MS Livingstone
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Squirrel monkeys normally lack ocular dominance columns in V1. This study
shows that squirrel monkeys can exhibit clear ocular dominance columns if
they are made strabismic within a few weeks of birth. Columns were seen
only in layer 4C beta and were coarser than the overlying blob pattern in
the same animal. In physiological recordings from layer 4C of a normal
squirrel monkey, single units were mostly monocular, but units driven by
the two eyes were intermixed. These results suggest that in squirrel
monkeys activity-dependent mechanisms do normally segregate geniculate
inputs from the two eyes, but on a much finer scale than in Old World
primates. Strabismic owl monkeys also showed ocular dominance columns;
normal owl monkeys showed variable expression. Because ocular dominance
columns, when present in New World monkeys, tend to occur in later-maturing
parts of layer 4C, I hypothesize that a difference in the relative timing
of the maturation of geniculocortical inputs and intracortical lateral
connectivity explains the variability of ocular dominance column expression
in New World monkeys.