Search PubMed⌕ Search

Biomedical subjects

B R Wooten

Publications and source records attributed to B R Wooten.

30 records · Page 2Linked to original sources
PubMed1983

The possible elemental nature of brown.

The continuous judgmental color-naming technique was used to assess the elemental nature of names descriptive of dark colors. Subjects were instructed to describe the color of a 0.54 deg. 2.5 log td test field of either 450, 530, 580 or 660 nm, that was surrounded by an achromatic annulus of 3.8 deg outer diameter. The annulus was varied in retinal illuminance from 1.5 to 3.7 log td. Test field and annulus were flashed simultaneously for 1 sec to the fovea of one eye. Results from 3 subjects indicated that the names blue, green, red and black were necessary and sufficient for describing the 450, 530 and 600 nm test fields. The 580 nm test field required the color name brown, in addition to the names yellow and black, to describe it when intermediate surround intensities were used. Additional results suggested the possible elemental nature of the color name brown.

Color↗
PubMed1979

Opponent chromatic mechanisms: relation to photopigments and hue naming.

Opponent chromatic response functions were determined from monochromatic, equal-luminance stimuli from 400 to 700 nm for three observers using a hue cancellation procedure. The same observers scaled the hue of the stimuli using the terms red, green, yellow, and blue. The results showed that the hue scaling was accurately predicted from the cancellation functions using the model of Hurvich and Jameson. Theoretical curves were generated to fit the chromatic response functions with a linear combination of three cone photopigments. The theoretical photopigments were based on an idopsin nomogram with lambdamax at a = 435, beta = 530, and lambda = 562 nm. An estimate of the density of each observer's preretinal optic media was obtained in order to relate the photopigment absorption spectra to the psychophysical data. Good linear fits were obtained for each observer's red-green curve, but not for the yellow-blue curves. A nonlinear model with an expansive exponent was used to fit the yellow-blue response functions with the three theoretical photopigments.

Adult↗
PubMed1975

Photopic spectral sensitivity of the peripheral retina.

Photopic spectral sensitivity was determined in the mid- and far-peripheral retina by two methods. The first consisted of measuring increment thresholds on a background similar in spectral composition to CIE Source A. The resulting spectral-sensitivity functions displayed maxima at about 440 nm, in agreement with previous work. The second method consisted of measuring dark-adaptation curves following termination of the background. From these curves, spectral-sensitivity functions were derived for various times in the dark. The results showed that the 440 nm maximum quickly diminished. When photopic thresholds were estimated from the cone plateau of the dark-adaptation curves, the spectral-sensitivity functions peaked at about 550 nm and had much the same shape from the parafovea to the far periphery. We suggest that previous findings of maximum photopic sensitivity in the short-wave region of the spectrum resulted from chromatic adaptation induced by backgrounds (such as Source A) that were weighted towards middle and long waves.

Adult↗
PubMed1973

Color-vision mechanisms in the peripheral retinas of normal and dichromatic observers.

It is possible that so-called normal trichromatic vision occurs only between the central blue-blind fixation area and about 30 degrees peripherally. Beyond about 30 degrees vision has been alleged to become dichromatic (red-green blind), and beyond about 60 degrees , monochromatic. Hence every form of color blindness may characterize various zones of the normal retina. We have studied mechanisms of peripheral color vision, mainly by measuring the spectral sensitivities of the blue-, green-, and red-sensitive systems, isolated by differential color adaptation. In normal observers the sensitivity of the blue-mechanism falls off about 2 log units by 80 degrees out. The green- and red-sensitive systems decline only about 0.7 log unit over the same range. Protanopes, deuteranopes, and tritanopes exhibit comparable changes. We have not found any color mechanism present centrally to be wholly lost peripherally. Nor, for dichromats, have we found any mechanism missing centrally to be present peripherally. Whatever evidences of peripheral color blindness have been observed appear to involve other mechanisms than failure of receptors, probably including some fusion of neural pathways from receptors to centers.

Color Perception↗