Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CHROMATES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,675 records · Page 93Linked to original sources
PubMed1971

Chromatic sensitivity and spatial organization of cat visual cortical cells: cone-rod interaction.

1. Colour sensitivity and spatial organization were determined for the dominant-eye receptive fields of thirty-eight simple or complex cells in cat primary visual vortex. Receptive fields were all from the cortical area associated with central vision. Each cell was investigated with threshold or suprathreshold monochromatic stimuli, under scotopic, low and high mesopic adaptation.2. The Purkinje shift, well defined for all units, was consistent with dual input from each of only two receptor mechanisms, viz. 556 nm cones and 500 nm rods. With change of adaptation level there was a systematic change in the peak sensitivity of spectral response curves to suprathreshold monochromatic stimuli, equated for quantum flux but of different wave-length. Equally with change of adaptation, the relative shift in threshold between wave-lengths selective for cone or rod activation was in close agreement with the change predicted from the Dartnall nomogram curves for visual pigments 556 and 507 respectively.3. For ganglion cells with concentric fields rod input derives from a spatially larger area than cone input. Rod field centre and rod field surround are substantially larger than the corresponding centre and surround for cones (Andrews & Hammond, 1970b). For cortical cells a conclusive comparable change could only be demonstrated for one simple unit. Its receptive field consisted of a horizontal excitatory stripe with asymmetric inhibitory flanks. When light-adapted the weaker, upper flank was functionally undetectable, indicative of purely rod input to this sideband, and the preference for upward movement was enhanced.4. No difference in receptive field configuration, or in spatial extent of input mediated by cones or by rods, was detected for any other unit. The discrepancy between retinal and cortical findings is discussed. It is inferred that cortical fields are compounded essentially by convergent input from geniculate cell field-centres.

Adaptation, Ocular↗
PubMed1972

Chromatic sensitivity and spatial organization of LGN neurone receptive fields in cat: cone-rod interaction.

1. The results described are for detailed analyses of fifty-four isolated LGN units, in response to monochromatic stimuli presented against achromatic, mid-mesopic backgrounds. Forty-seven were positively identified cells from the A-laminae; the remaining seven were fibres from the optic radiation.2. Cells are classified according to firing pattern. Phasic cells respond almost exclusively with a discharge transient. Tonic cells, by contrast, give a maintained component in addition. In general, tonic cells possess higher spontaneous firing frequencies than phasic cells and the antagonistic surrounds of their receptive fields are more potent. In other respects the two classes appear to be functionally similar.3. All cells within the A-laminae receive input involving both rods and 556 nm cones.4. The spatial organization of geniculate receptive fields, unlike retinal fields, is little different for cone and rod vision. In the infrequent instances where a change is apparent, it is small and can go in either direction: rod fields are then on balance slightly larger than cone fields.5. The locus of maximum sensitivity for the receptive field surround is described by a circle, concentric with the field centre; it is invariant with respect to stimulus geometry, or changeover from cone to rod vision.6. This result implies that the receptive field surround mechanism does not extend through the field centre. It supports the notion that the centre and surround of each geniculate cell receptive field are mediated by discrete retinal inputs.

Action Potentials↗
PubMed2005

Chromatic adaptation of photosynthetic membranes.

Many biological membranes adapt in response to environmental conditions. We investigated how the composition and architecture of photosynthetic membranes of a bacterium change in response to light, using atomic force microscopy. Despite large modifications in the membrane composition, the local environment of core complexes remained unaltered, whereas specialized paracrystalline light-harvesting antenna domains grew under low-light conditions. Thus, the protein mixture in the membrane shows eutectic behavior and can be mimicked by a simple model. Such structural adaptation ensures efficient photon capture under low-light conditions and prevents photodamage under high-light conditions.

Adaptation, Biological↗
PubMed1967

Monocular and binocular aftereffects of chromatic adaptation.

Supersaturated greens seen after long-wavelength adaptation depend upon contrast from the continuing afterdischarge of bleached "red" receptors in the surround, rather than merely upon inactivation from bleaching of "red" receptors in the test spot area. When test spot and bleach field coincide spatially, supersaturated greens are not seen. Since color mixing but not contrast was found binocularly, color contrast must be a retinal phenomenon.

Adaptation, Ocular↗
PubMed1972

Chromatic specificity of the visual evoked response.

The temporal alternation of red and green stripes in a structured field produces successive contrast, which can elicit cortical potentials recorded from the scalp. Amplitudes of the major frequency components of the potentials correspond to the relative intensities of red and green producing the contrast. The amplitude variations are color-specific, since total luminance and structure are held constant.

Color Perception↗
PubMed1977

Chromatic organization of primate cones.

The distribution of baboon retinal cones were mapped histochemically by light-stimulated reduction of nitroblue tetrazolium chloride. Blue cones were distributed regularly in the periphery: red and green cones were distributed randomly everywhere. The ordering of cone densities was green > red > blue.

Animals↗
PubMed1994

Reduction of Chromate by Desulfovibrio vulgaris and Its c(3) Cytochrome.

Washed cell suspensions of Desulfovibrio vulgaris rapidly reduced Cr(VI) to Cr(III) with H(2) as the electron donor. The c(3) cytochrome from this organism functioned as a Cr(VI) reductase. D. vulgaris may have advantages over previously described Cr(VI) reducers for the bioremediation of Cr(VI)-contaminated waters.

Journal Article↗
PubMed2005

Color of scents: chromatic stimuli modulate odor responses in the human brain.

Color has a profound effect on the perception of odors. For example, strawberry-flavored drinks smell more pleasant when colored red than green and descriptions of the "nose" of a wine are dramatically influenced by its color. Using functional magnetic resonance imaging, we demonstrate a neurophysiological correlate of these cross-modal visual influences on olfactory perception. Subjects were scanned while exposed either to odors or colors in isolation or to color-odor combinations that were rated on the basis of how well they were perceived to match. Activity in caudal regions of the orbitofrontal cortex and in the insular cortex increased progressively with the perceived congruency of the odor-color pairs. These findings demonstrate the neuronal correlates of olfactory response modulation by color cues in brain areas previously identified as encoding the hedonic value of smells.

Adult↗
PubMed1988

Simultaneous processing of spatial and chromatic components of patterned stimuli by the human visual system.

We report measurements on discrimination of orientation and magnification made for elements differentiated in colour and/or luminance from their background. By performing measurements at a series of background luminances and for fixed luminance of the elements, we show that with colour contrast, discrimination for both spatial parameters is unimpaired when the background is at isoluminance with the elements. Under simple luminance contrast, however, these discriminations become poorer when the background luminance is within some +/- 5% of that of the elements, and are completely absent when the two values are the same. A deuteranomalous subject is unable to make the spatial discrimination around the isoluminance point for colour contrasts which are too small for him to distinguish, but for which subjects with normal colour vision maintain spatial discriminations at isoluminance. This observation establishes that the physiological mechanisms of normal colour vision, rather than stimulus artefacts, mediate the observed spatial discriminations. We conclude that the visual processing of colour and spatial parameters such as orientation and magnification are intrinsically related to each other.

Adult↗