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Results for “Color Perception Tests”

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At least 505 records · Page 28Linked to original sources
PubMed1991

Two systems for colour-naming defects: verbal disconnection vs colour imagery disorder.

Two subjects affected by pure alexia and showing no central dyschromatopsia or generalized aphasia, performed poorly on traditional tasks with visually-presented colour stimuli and on tasks with objects presented verbally. Three experiments were conducted to evaluate the possible role of mental colour imagery in recalling the colours of objects from memory. It was concluded that Case I, with left occipital lobe softening, had preserved imagery systems, but failed to recode the colours of mentally generated colour images, just as he failed to name visually presented colours, suggesting a language-imagery disconnection. In contrast, Case II, with a bilateral occipital lesion, had sustained damage to her long-term visual memories for colours as chromatic attributes of objects. This content-specific imagery deficit was concomitant with colour agnosia. The present findings are discussed in terms of current cognitive theories on imagery deficits.

Aged↗
PubMed1996

Preserved color imagery in an achromatopsic.

The loss of color vision secondary to central nervous system disease (achromatopsia) is thought to preclude visual imagery of colors. We report a patient with achromatopsia, secondary to bilateral temporo-occipital infarcts inclusive of the lingual and fusiform gyri, with preserved color imagery. Our findings, in conjunction with previous cases in the literature, are consistent with a single neural network for color processing in which a disconnection of internal activation from stored color representations produces impaired color imagery with preserved color perception, whereas a disconnection of visual input to these representations produces achromatopsia with preserved color imagery.

Cerebral Infarction↗
PubMedDate not supplied

What do color blind children really see? Guidelines for clinical prescreening based on recent findings.

Recent research on classical red-green blind observers has shown that complete dichromacy may be present only under conditions where the viewing angle is small. For viewing angles greater than about 4 degrees, both rods and an anomalous cone have been shown to underlie a weak form of trichromacy. The conditions for rod or anomalous cone mediation of this trichromacy have also been shown to depend on the overall viewing luminance. These data taken together prompt a rethinking of the classical view of red-green dichromacy and lead to new considerations of the color discrimination performance of dichromatic candidates. In this paper we review the recent research on the presence of trichromatic abilities in classical dichromats and we relate these findings to the needs of the clinician, especially in the screening of young children.

Child↗
PubMedDate not supplied

Acquired dyschromatopsias.

Theories of color vision have been founded on behavioral observations of how the human eye distinguishes colors and mixtures of colors. Studies of congenital dyschromatopsias (inherited disorders of color vision) have been important to the development of these theories. Subsequent studies of acquired dyschromatopsias (disorders of color vision caused by disease) were understandably influenced by these concepts. Theories to explain the patterns of color vision impairment found in acquired diseases (for example, preferential hue discrimination defects) have stressed the likelihood of selective damage to specific components of the afferent visual system (photoreceptors, ganglion cells, synaptic elements, axons etc.). More recent evidence suggests, however, that impairment of color vision by diseases of the retina and optic nerve is commonly nonspecific, and not the result of selective impairment of individual neural mechanisms responsible for mediating color vision. Rather, the patterns of acquired dyschromatopsias often appear to be related to a physiologically heterogeneous distribution of color vision in the foveal and perifoveal visual field, coupled with a tendency for the visual field defects caused by acquired diseases to be unevenly distributed in these same areas.

Color Perception Tests↗