The Journal of Neuroscience, March 1, 2000, 20(5):2043-2053
Fine Structure of Parvocellular Receptive Fields in the Primate
Fovea Revealed by Laser Interferometry
Matthew J.
McMahon,
Martin J. M.
Lankheet,
Peter
Lennie, and
David R.
Williams
Center for Visual Science, University of Rochester, Rochester, New
York 14627
Optical blurring in the eye prevents conventional physiological
techniques from revealing the fine structure of the small parvocellular
receptive fields in the primate fovea in vivo. We explored the organization of receptive fields in macaque parvocellular lateral geniculate nucleus cells by using sinusoidal
interference fringes formed directly on the retina to measure spatial
frequency tuning at different orientations. Most parvocellular cells in and near the fovea respond reliably to spatial frequencies up to and
beyond 100 cycles/° of visual angle, implying center input arising
mainly from a single cone. Temporal frequency and contrast response
characteristics were also measured at spatial frequencies up to 130 cycles/°. We compared our spatial frequency data with the frequency
responses of model receptive fields that estimate the number,
configuration, and weights of cones that feed the center and surround.
On the basis of these comparisons, we infer possible underlying
circuits. Most cells had irregular spatial frequency-response curves
that imply center input from more than one cone. The measured responses
are consistent with a single cone center together with weak input from
nearby cones. By exposing a fine structure that cannot be discerned by
conventional techniques, interferometry allows functional measurements
of the early neural mechanisms in spatial vision.
Key words:
spatial vision; ganglion cells; LGN; parvocellular; acuity; interferometry; retinal circuitry
Copyright © 2000 Society for Neuroscience 0270-6474/00/2052043-11$05.00/0