The Journal of Neuroscience, June 15, 2001, 21(12):4416-4426
Oriented Axon Projections in Primary Visual Cortex of the Monkey
Lawrence C.
Sincich and
Gary G.
Blasdel
Program in Neuroscience and Department of Neurobiology, Harvard
Medical School, Boston, Massachusetts 02115
One important aspect of the functional architecture of primary
visual cortex is the circuitry that accounts for the receptive field
properties of neurons. The anatomy that underlies retinotopy and ocular
dominance is well known, but no anatomical structure related to
orientation selectivity has been found in primates. We examined whether
the arrangement of local axon systems projecting within the cortical
layers might be correlated with orientation preference in New World
monkeys. We found that axons in layer 3 spread out from the site of a
tracer injection in an anisotropic manner and that this elongated
distribution is aligned with the preferred orientation recorded at each
site. Moreover, within a few degrees of the foveal representation, the
majority of the axon terminals fall within or just outside of the
limits of the cortical mapping of the classical receptive field. Thus
local axons produce a field of monosynaptic excitation that aligns with orientation axes and reaches neurons that have receptive fields which
are adjacent in visual space.
Key words:
visual cortex; New World primate; axon projections; orientation selectivity; retinotopy; receptive field
Copyright © 2001 Society for Neuroscience 0270-6474/01/21124416-11$05.00/0