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Biomedical subjects

C Noorlander

Publications and source records attributed to C Noorlander.

6 recordsLinked to original sources
PubMed1986

Deplasticizing of thick Epon sections involving a new adhesive technique and staining of nervous tissue.

The present communication deals with a technique developed for the selective staining of neural tissue in thick (10 micron) Epon sections. A new adhesive method was needed, because the known techniques are only applicable to 0.5-2 micron thin sections. The critical step in the procedure is the adhesion of the sections onto the slides. This is accomplished by heating the sections on top of a uniform layer of albumin glycerol on the slide followed by coating with celloidin. The results after deplasticizing and coagulation with this technique are comparable to those obtained by paraffin or frozen section techniques, but in addition have the advantage of Epoxy resin embedding e.g. the possibility of cutting undecalcified hard tissues and sections for serial reconstruction.

Adhesives↗
PubMed1983

Sensitivity to spatiotemporal colour contrast in the peripheral visual field.

Contrast detection thresholds for spatiotemporal colour modulation were determined at several retinal locations. Colour discrimination is studied for red-green modulation of a yellow field and for yellow-blue modulation of a white field. For constant target size colour vision deteriorates if the stimulus is moved away from the fovea, but if the shift is combined with a suitable enlargement of the target size colour discrimination at the periphery is comparable to that at the fovea. We did not find any retinal location along the horizontal meridian which was red-green or yellow-blue colour blind. Chromatic bars were detected in the nasal peripheral retina at eccentricities of up to at least 50 degrees, temporal colour contrast was perceptible at nasal eccentricities of up to at least 90 degrees.

Color Perception↗
PubMed1983

Spatial and temporal discrimination ellipsoids in color space.

Three-dimensional discrimination ellipsoids are presented for a number of representative points in color space. These ellipsoids have been obtained not with the conventional split field but with flickering grating patterns. Thus our study extends the well-known results of Brown and MacAdam [J. Opt. Soc. Am. 39, 808-813 (1949)] to cases in which the image is structured in space and time. As expected, we find that the discrimination ellipsoids depend on the spatiotemporal structure of the stimulus. This has potential consequences for color-difference formulas as used in industry and commerce: no single formula will do when it is important to treat patterns with different structure. We present analytical descriptions, based on the Vos-Walraven [Vision Res. 12, 1327-1365 (1972)] line element augmented with spatiotemporal frequency-dependent coefficients that fit our results reasonably well. For coarse gratings (approximately 1 cycle per degree) or slowly modulated fields (approximately 1 Hz) our results prove to be compatible with the results of Brown and MacAdam obtained with a bipartite 2 degree field.

Color Perception↗
PubMed1981

Sensitivity to spatiotemporal combined luminance and chromaticity contrast.

Contrast-detection thresholds for various combinations of chromaticity and luminance differences were obtained for spatiotemporal square-wave modulation of a yellow field. The results are expressed in terms of excitation of the Vos-Walraven R,G primaries. For every spatiotemporal frequency the thresholds can be approximated by an ellipse in the red-green plane. Large variations were found in the orientation, magnitude, and eccentricity of the discrimination ellipses. It seems that a simple threshold function appears to be sufficient to describe the experimental data. Although the eye does not perceive hue contrast for high spatial frequencies, its sensitivity is not governed mainly by summation of the red and green channels.

Color↗
PubMed1980

Influence of the target size on the deterction threshold for luminance and chromaticity contrast.

The effect of the target size on the detecton of luminance and chromaticity flicker and gratings was studied. Discrimination ellipses in a luminance-chromaticity plane were determined with square test areas subtending from 1/4 degree to 1 degree. Pure luminance modulation thresholds and pure chromaticity modualtion thresholds were obtained from square targets subtending from 1/16 degree to 2 degree. Square-wave stimuli were presented on a color television monitor; the mean color of the screen was yellow, the average retinal illuminance was 350 td. The main effect of enlarging the field size is that the threshold for any luminance-chromaticity combination decreases monotonically except when spatial frequencies are high. The summation area for detecting a fine bar pattern is at least 8 x 8 periods; the integration area for detecting flicker is more than 1 degree x 1 degree. This holds for any luminance-chromaticity mixture. For a fixed spatial or a fixed temporal frequency the change in sensitivity sometimes depends strongly on the ratio of luminance modulation to chromaticity modulation. The main conclusion of this study is that if a target is predominantly yellow the target size has similar influence on the sensitivity to both luminance and chromaticity contrast.

Adult↗