Deoxyglucose Analysis of Retinotopic Organization in Primate Striate Cortex

Abstract

We have anatomically analyzed retinotopic organization using the 14C-labeled 2-deoxy-D-glucose method. The method has several advantages over conventional electrophysiological mapping techniques. In the striate cortex, the anatomical substrate for retinotopic organization is surprisingly well ordered, and there seems to be a systematic relationship between ocular dominance strips and cortical magnification. The 2-deoxyglucose maps in this area appear to be largely uninfluenced by known differences in long-term metabolic activity. This method should prove useful in analyzing retinotopic organization in various visual areas of the brain and in different species.

Positional uncertainty in peripheral and amblyopic vision

“…For testing of normal (control) observers, and for the nonamblyopic eyes, the stimulus was viewed from a distance of 8.46 m. At this distance the lines were 30' long and 2" wide. For testing the periphery the stimulus size was "scaled" in proportion to recent estimates of the cortical magnification factor (Dow et al, 1981;Tootell et al, 1982;Van Essen et uf., 1984). This scaling, found to be appropriate for vernier acuity and for 3dot bisection (Yap et al, in preparation), was accomplished by keeping the physical stimulus the same at all eccentricities and varying the viewing distance according to d = &/( 1 + E/0.77) where E is the eccentricity in degrees and df is the distance used for fovea1 viewing.…”

“…The threshold for a single sample (in the absence of spatial and temporal averaging) may provide an estimate of the intrinsic positional uncertainty of the visual system. For the periphery, positional uncertainty is high due to the wider spacing and increased irregularity of the cone mosaic (Hirsch and Miller, 1985), and the precipitous decrease in the cortical magnification factor (Dow et al, 1981;Tootell et al, 1982;Van Essen et al, 1984). What is of special interest here is that the threshold for a single sample is considerably larger than the intercone spacing at 2.5" (approximately 70 arc set), suggesting that it is the cortical sampling grain rather than the cone mosaic which limits position discrimation in the periphery.…”

“…However, in the normal periphery, the addition of spatial samples in the direction orthogonal to the discrimination cue reduces thresholds in proportion to the square root of the number of samples as would be expected in an ideal detector with uncorrelated noise at an early stage of visual processing. In normal peripheral vision, the high degree of spatial uncertainty with few samples can be understood on the basis of the anatomy and physiology of the retina and cortex which results in a sparse neural sampling grain (Rolls and Cowey, 1970;Dow et al, 1981;Tootell et al, 1982;Van Essen et al, 1985).…”

“…Moreover, the inverse cortical magnification factor (i.e. the number of degrees of visual space/mm of cortex) rises precipitously with eccentricity (Daniel and Whitteridge, 1961;Dow et al, 1981;Tootell et al, 1982;Van Essen et al, 1984;Perry and Cowey, 1985). While these profound alterations in the anatomy and physiology of the visual pathways occur within the central IO", the optics of the eye remain approximately constant (Jennings and Charman, 1981).…”

O debate da imagética mental

“…3 é um exemplo do padrão de ativação que ocorre na área visual V1 de macacos rhesus (Macaca mulatta) (discutido por Kosslyn et al, 2006, p. 16 (Tootell et al, 1982).…”