Processing Of Color Information Research Articles

Effects of Hemispheric Laterality on Color-Information Processing

This study investigated the interaction between hemispheric laterality and recognition memory for pictures presented in three different color modes: realistic, nonrealistic, and monochrome (black and white). Stimulus materials were 180 scenic slides (120 stimulus and 60 distractor) produced in three color modes. Materials were presented to a group of 26 graduate volunteers via the list learning procedure for a duration of 500 msec. each. During one-half of the materials an arithmetic masking task was performed to inhibit left-hemisphere processing. Signal-detection parameters, compared in a 2 x 3 repeated-measures design, produced significant interactions for the probability of hits, error, and d' measures. Post hoc tests indicated significantly higher hit probability and d' scores for nonrealistic color and higher error rates for realistic color under the right localized condition. Findings suggest that color processing is bilocational, realistic information is processed more deeply than nonrealistic, and nonrealistic color supplies unique color codes for storage and retrieval.

Ferroelectric liquid crystals: The development of devices

Abstract The discovery of ferroelectric liquid crystals (1974) together with the subsequent discovery of the surface-stabilized liquid crystals (1980) have enriched the family of ferroelectrics with a new, different and powerful member. At the same time it has considerably raised the performance level of liquid crystals as general electro-optic media and opened up new opportunities in domains where fast processing is necessary, for instance in optical computing. The last few years have seen an important development in the technology of surface-stabilized ferroelectric liquid crystal (SSFLC) devices, which today offers solutions for full dynamic grey scale, full color, high speed, high resolution and high information processing and storage. An example of a very demanding industrial application now attracting the SSFLC approach and where the full range of the SSFLC potential will be required, is the large and flat screen high definition television (HDTV). In this paper we review some key events in the resea...

Parallel processing of motion and colour information

When the two eyes are confronted with sufficiently different versions of the visual environment, one or the other eye dominates perception in alternation. A similar situation may be created in the laboratory by presenting images to the left and right eyes which differ in orientation or colour. Although perception is dominated by one eye during rivalry, there are a number of instances in which visual processes nevertheless continue to integrate information from the suppressed eye. For example the interocular transfer of the motion after-effect is undiminished when induced during binocular rivalry. Thus motion information processing may occur in parallel with the rivalry process. Here we describe a novel example in which the visual system simultaneously exhibits binocular rivalry and vision that integrates signals from both eyes. This apparent contradiction is resolved by postulating parallel visual processes devoted to the analyses of colour and motion information. Counterphased gratings are viewed dichoptically such that for one eye the grating is composed of alternating yellow and black stripes (luminance) while for the other it is composed of alternating red and green stripes (chrominance). When the gratings are fused, a moving grating is perceived. A consistent direction of motion can only be achieved if left and right monocular signals are integrated by the nervous system. Yet the apparent colour of the binocular percept alternates between red-green and yellow-black. These observations demonstrate the segregation of processing by the early motion system from that affording the perception of colour. Although, in this stimulus, colour information in itself can play no part in the cyclopean perception of motion direction, colour is carried along perceptually (filled in) by the moving pattern which is integrated from both eyes.

Bees perceive illusory colours induced by movement

Certain black-and-white patterns, when rotated at appropriate speeds, can create the artificial perception of hues. We report that this illusion is not confined to human vision, but is also perceived by an insect, the honeybee. The findings suggest that certain features underlying the processing of colour information are shared by man and bee.

Processing of color, form and disparity information in visual areas VP and V2 of ventral extrastriate cortex in the macaque monkey

The responses of single cells to light bars of different orientation, direction of motion, speed, binocular disparity, and wavelength were systematically analyzed in areas V2 and VP of ventral extrastriate visual cortex in the macaque monkey. Selectivity for each of these parameters was assessed quantitatively using computer-controlled procedures. In both VP and V2 (both representing the superior contralateral quadrant), more than half of the cells studied were selective for stimulus color and more than half for stimulus orientation. In contrast, only a small minority of the VP and V2 cells were selective for the direction of stimulus motion. Comparison with reports of single-unit properties in dorsal extrastriate cortex suggests there are no major differences in the incidence of orientation, direction, and color selectivity between ventral and dorsal subdivisions of V2. Between V3 and VP, though, there are marked differences: Color-selective cells are much less common in V3 than VP, whereas direction-selective cells are more common in V3. This dorsoventral difference in the distribution of neuronal response properties suggests a significant asymmetry in the way visual information is processed in upper and lower parts of the visual field. The properties of cells in VP suggest that it plays an important role in both form and color vision, similar to that attributed to area V4.

Laminar origin of direct projection from cortex area V1 to V4 in the rhesus monkey

Direct projection from cortex area V1 to V4 in the rhesus monkey was demonstrated by means of retrograde axonal transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). This projection originated at the layers 2 and 3 of the only representation area of central visual field (0-6 degrees) in V1 and terminated at the central representation of V4, whereas there was no projection between the extracentral representations of V1 and V4. Correlation of the present finding with the previous findings suggests that this projection is predominantly involved in the system of color information processing.

Relation of spectral types to oil droplets in cones of turtle retina.

The spectral sensitivities and color of oil droplets of cone photoreceptors in the retina of the red-eared turtle (Pseudemys scripta elegans) were investigated by intracellular recording and injections of Lucifer yellow dye. Six morphological types of cones could be distinguished by the color of the oil droplets located in the outermost inner segments. Single cones containing either red or pale green oil droplets were sensitive to red light, cones with yellow oil droplets to green, and cones with clear oil droplets to blue. Contrary to previous reports, both principal and accessory members of double cones were sensitive to red, and no diffusion of dye was detected between the two apposed members. Thus, the oil droplets provide a reliable morphological basis for further investigation of the neuroanatomical networks underlying the processing of color information in the vertebrate retina.

Color Contrast Perimetry: The Spatial Distribution of Color Defects in Optic Nerve and Retinal Diseases

Color contrast perimetry was used to evaluate central visual field defects in a group of 28 patients with visual loss resulting from optic nerve or retinal diseases. Kinetic. perimetry was performed using colored test objects of constant luminance, equated to a white surround of 10 ft lamberts. Colored test objects were varied in size and in extent of color saturation. Test object color saturation was varied from a white that matched the color and luminance of the adapting background toward either the blue or the red color maxima of a video tangent screen. All central visual field defects that were demonstrable by luminance contrast perimetry were also detected by color contrast testing, and no defects were found for color contrast detection that could not also be demonstrated by conventional luminance increment perimetry. Retinal diseases usually produced scotomas for both color and luminance contrast detection, while optic nerve disorders tended to produce global depressions of both color and luminance contrast sensitivity across the entire visual field in addition to scotomas. There was no systematic difference in visual field defects for either class of disease when comparing color contrast in the blue (tritan) versus the red (protan) axes of color space. The apparent tritan or protan/deutan axes of color confusion found by hue discrimination testing in acquired dyschromatopsias may be determined by the relative spatial distribution of defects in the central visual field rather than by selective impairment of neural mechanisms for color or luminance information processing.

Anatomy and physiology of a color system in the primate visual cortex

Staining for the mitochondrial enzyme cytochrome oxidase reveals an array of dense regions (blobs) in the primate primary visual cortex. They are most obvious in the upper layers, 2 and 3, but can also be seen in layers 4B, 5, and 6, in register with the blobs in layers 2 and 3. We compared cells inside and outside blobs in macaque and squirrel monkeys, looking at their physiological responses and anatomical connections. Cells within blobs did not show orientation selectivity, whereas cells between blobs were highly orientation selective. Receptive fields of blob cells had circular symmetry and were of three main types, Broad-Band Center-Surround, Red-Green Double-Opponent, and Yellow-Blue Double-Opponent. Double-Opponent cells responded poorly or not at all to white light in any form, or to diffuse light at any wavelength. In contrast to blob cells, none of the cells recorded in layer 4C beta were Double-Opponent: like the majority of cells in the parvocellular geniculate layers, they were either Broad-Band or Color-Opponent Center-Surround, e.g., red-on-center green-off-surround. To our surprise cells in layer 4C alpha were orientation selective. In tangential penetrations throughout layers 2 and 3, optium orientation, when plotted against electrode position, formed long, regular, usually linear sequences, which were interrupted but not perturbed by the blobs. Staining area 18 for cytochrome oxidase reveals a series of alternating wide and narrow dense stripes, separated by paler interstripes. After small injections of horseradish peroxidase into area 18, we saw a precise set of connections from the blobs in area 17 to thin stripes in area 18, and from the interblob regions in area 17 to interstripes in area 18. Specific reciprocal connections also ran from thin stripes to blobs and from interstripes to interblobs. We have not yet determined the area 17 connections to thick stripes in area 18. In addition, within area 18 there are stripe-to-stripe and interstripe-to-interstripe intrinsic connections. These results suggest that a system involved in the processing of color information, especially color-spatial interactions, runs parallel to and separate from the orientation-specific system. Color, encoded in three coordinates by the major blob cell types, red-green, yellow-blue, and black-white, can be transformed into the three coordinates, red, green, and blue, of the Retinex algorithm of Land.

Effect of Encoding Instructions on Children's Spatial and Color Memory: Is There Evidence for Automaticity?

This experiment is concerned with assessing whether there is evidence for the automatic processing of spatial and color information by children and with the development of control of encoding operations. First, third, and fifth graders viewed pictures of simple objects that varied in color (red or green) and spatial location (left or right). Subjects were instructed to encode (a) only the item, (b) the item and its color, (c) the item and its position, (d) the item, its color, and its position. The data yielded evidence for nonchance incidental memory of spatial, but not color, information. The data also suggested that children at all age levels were able to control their encoding operations similarly, as there was no evidence for an interaction of development with encoding instructions. These findings are discussed with respect to a model for automatic encoding processes and work on memory for central and incidental information.

Spatial decay properties of L‐type horizontal cell response in the retina

AbstractThis paper discusses the propagation of potentials in the receptor field of horizontal cells in the retina and the linearity of response of horizontal cells with respect to the photoreceptor input. A microelectrode is inserted into the L‐type horizontal cells of carp and, by stimulating various portions of the retina by a small light spot, the response potential of L‐type horizontal cells is measured. As a result, the amplitude of the response potential exhibits a decay depending only on the distance between the horizontal cell and the point of stimulus, without any directivity in the propagation of potential. In other words, it is shown that the receptor field of the L‐type horizontal cells is spatially uniform with respect to the propagation of potential. On the other hand, when the input from the photoreceptor, is increased by increasing the light spot intensity or by using a wavelength of higher sensitivity, the spatial decay of the response potential of L‐type horizontal cells decreases. This result seems to indicate that L‐type horizontal cells have a saturating nonlinearity in regard to the input from the photoreceptor. The response characteristics of the horizontal cells in this paper are essential in the analysis of color information processing or picture information processing in the retina.

Neurographic evidence in alcoholic neuropathy : D. Kountouris, M.E. Dughly, J. Haan and J. Milonas (Bochum, W. Germany)

The relationship between the neural processing of color and motion information has been a contentious issue in visual neuroscience. We examined this relationship directly by measuring neural responses to isoluminant S cone signals in extrastriate area MT of the macaque monkey. S cone stimuli produced robust, direction-selective responses at most recording sites, indicating that color signals are present in MT. While these responses were unequivocal, S cone contrast sensitivity was, on average, 1.0–1.3 log units lower than luminance contrast sensitivity. The presence of S cone responses and the relative sensitivity of MT neurons to S cone and luminance signals agree with functional magnetic resonance imaging (fMRI) measurements in human MT+. The results are consistent with the hypothesis that color signals in MT influence behavior in speed judgment tasks.

Stroop effect: interference and facilitation with verbal and manual responses.

Two groups of 12 volunteers manually (button pushing) or verbally identified the ink color of 5, randomly ordered and tachistoscopically presented, kinds of stimulus conditons, specified by the nature of the noncolor information and the relationship between color and noncolor information: Congruent Color Words, Noncolor Words, Scrambled Color Words, Nonword Geometric Shapes, and Noncongruent Color Words. With verbal response, facilitation of reaction time occurred for Congruent Color Words compared to Scrambled Color Words and Noncolor Words but not when compared to the Nonword Control, while with manual response facilitation appeared for all comparisons. Interference appeared for both groups, with Noncongruent Color Words having the slowest reaction time. The present design corrected for inadequacies in previous studies and more firmly established the conclusion of parallel perceptual processing of color and noncolor information, with facilitation/interference effects being localized in postperceptual decision operations of signal summation and response competition.

The effects of pause time on auditory comprehension of aphasic subjects

Aphasic subjects performed a modified version of the Token Test, in which 5 sec pauses were placed at various points in some of the spoken commands in the test. Insertion of pauses generally resulted in substantial improvements in the subjects' ability to carry out the commands. The location of the pauses in the commands did not appear to substantially affect subjects' performance. The results suggest that an insertion of a 5 sec pause may facilitate processing of color, size, and shape information, but not processing of locational or relational information.

Sinusoidal flicker characteristics of the color-sensitive mechanisms of the eye

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Single unit activity in the visual pathway of the butterfly Heliconius erato

Extracellular potentials were recorded from the optic lobes, protocerebrum, and ventral nerve cord of the neotropical butterfly Heliconius erato adanis. Except for pure ‘on’ and ‘off’ fibres, all neurons demonstrated a dark discharge. Neurons demonstrating a special sensitivity to unidirectional movement, jittery movement, dimming, unilateral stimulation, illumination level, etc., were studied. It is questionable whether neurons responding to such stimuli are homologous in all insects. A hypothesis concerning the neural processing of colour information is presented.