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PubMed1975

[Colour naming deficit in aphasic and non-aphasic brain damaged patients (author's transl)].

We have examined the severity and quality of aphasic misnaming in colour naming tasks as compared to errors of patients with right-sided brain damage and to patients with posterior disconnexion syndrome. The investigation is based on 80 aphasic patients, 20 patients with right-sided brain damage and 80 normal control subjects. Differences in the performance for colour and object naming are discussed. The main results were: 1. The subtypes of aphasia did not differ quantitatively in both types of performance. All aphasics made significantly more errors on colour naming than on object naming tasks. This difference, however, was numerically too small to have practical value. 2. Unlike in the corresponding understanding tasks, both types of naming tasks differentiated between aphasic and non-aphasic patients, the aphasic group performing poorer. 3. The four subtypes of aphasia had similar error scores in the 10 colour tasks. We observed certain regularities in the type of paraphasic misnaming for the total group of aphasics. The subgroup of amnesic aphasia was characterized by a strategy of modifying the colour terms similar to the description of use encountered in the language behavior of these patients. 4. Patients with posterior disconnexion syndrome in general make 7 errors out of 10 tasks in colour naming, in contrast to 2 errors out of 10 tasks in object naming. For aphasic patients the relation is 3.5 to 2.5 errors.

Adolescent↗
PubMed1981

Scaling of color sensation by magnitude estimation: a contribution to opponent-colors theory.

Saturation and hue perceived in monochromatic stimuli and in light mixtures were scaled psychophysically by a direct magnitude estimation method. The colors were of aperture mode and were presented against a dark background. As a result opponent-colors functions were obtained which show the hue sensations produced by the lights of the visible spectrum (under the observing conditions used). Compared to the opponent-colors functions of Hurwich and Jameson, obtained by a cancellation technique, the subjective hue sensation differed significantly. It may be concluded that these cancellation functions describe an earlier, probably a retinal level of data processing, while our results may be regarded as a description of the output of the color vision system.

Color Perception↗
PubMed1990

X-linked congenital retinoschisis.

The natural history and electrophysiological findings of 52 patients with X-linked congenital retinoschisis with a follow-up of up to 26 years are described. The mean visual acuity was reduced to 0.24 +/- 0.2 and remained unchanged in most patients during this time. If visual loss occurred, it usually happened in the first decennium. The complications were retinal detachments in 11% and vitreous hemorrhages in 4% of the eyes. In general, the vitreous hemorrhages resolved spontaneously. Retinal detachments were treated successfully with conventional buckling procedures. Redetachments occurred in about 40%. Prophylactic laser coagulation was of no use because it was complicated by detachment in 43% of our series. The electro-oculogram was usually normal. In addition to the known electrorentinographic findings of normal a-wave and reduced b-wave amplitudes, we found prolonged b-wave latencies and implicit times, as well as a reduced 30 Hz flicker response.

Adolescent↗
PubMed1993

Disturbance of colour perception in Parkinson's disease.

A computer-aided method for the determination of colour fusion time (CFT) was developed. CFT indicates the acuity of the perception of monochromatic contours. CFT was determined in 36 patients with Parkinson's disease (PD) and compared with a group of 36 age- and sex-matched controls. Patients with PD generally had a shortened fusion time, especially for dark-green, light-blue and dark-red stimuli. The results give evidence to the hypothesis of a colour perception disorder in PD. The physiological and pathoanatomical basis of this phenomenon is unknown, but a functional deficit of cortical neurons may be a probable cause.

Adult↗
PubMedDate not supplied

Comparative neurobiology of color vision in humans and animals.

Discrimination of colors was studied using an instrumental learning paradigm in monkeys (Macaque rhesus) and fishes (Carpio cyprinus L.). The confusion matrices composed of probabilities of instrumental responses were treated by factor analysis. The spherical structure of perceptual color space revealed in both animals was similar to that in humans. The four eigenvectors constituting the four-dimensional Euclidean hypersphere correspond to "red-green," "blue-yellow," "brightness," and "darkness" neuronal channels.

Animals↗
PubMed1998

Pain and Stroop interference tasks activate separate processing modules in anterior cingulate cortex.

Investigations of pain using functional imaging techniques have revealed an extensive central network associated with nociception. This network includes the thalamus, insula, prefrontal cortex and anterior cingulate cortex (ACC) as well as the somatosensory cortices. Positron emission tomography (PET) of regional cerebral blood flow (rCBF) has demonstrated activation of the ACC during cognitively challenging tasks such as the Stroop interference task and divided attention. One interpretation of this research is that ACC is involved in the general features of attention and that it does not play a specific role in pain processing per se. Three-dimensional PET imaging provides a method for assessments of rCBF in a single individual during multiple tasks. In addition, coregistration of PET and magnetic resonance (MR) images allows for better localisation of the PET signals so that differences in cortical activation sites can be more accurately determined. This approach was used to assess rCBF during the experience of pain by subtracting images collected during heat from those during noxious heat stimulation. Two regions of the ACC had elevated rCBF, one in the perigenual region and one in the mid-rostrocaudal region (i.e. midcingulate cortex). During the execution of the Stroop task, the group result showed the midcingulate region overlapping with the site seen during the experience of pain. This group result, however, was not confirmed in the individual subject analysis, which revealed widespread and independent areas of ACC response to pain and Stroop. It is concluded that the ACC contributes to multiple cognitive procedures. It is inadequate to describe the primary contribution of ACC to pain processing as "attention" because it is unlikely that the multiple small and independent activation sites produced by pain and Stroop subserve attentive processing throughout the brain.

Adult↗
PubMed2004

Goldfish color vision sensitivity is high under light-adapted conditions.

The wavelength discrimination threshold of three goldfish was examined in a series of behavioral experiments. Using an auto-shaping technique, detection thresholds were established for 531 and 648 nm spectral increments presented on a 6.6 cd m(-2) white background. Next, discrimination between the wavelengths was established at equal, suprathreshold, intensities. Finally, the intensities of the two stimuli were reduced to establish the intensity threshold for the wavelength discrimination. The results indicate that goldfish, like several mammalian species, can discriminate wavelength at detection threshold intensity. This finding suggests that high color sensitivity is not confined to mammals or dependent upon a very high percentage of wavelength opponent ganglion cells. Rather, high color vision sensitivity may be based upon an inherent sensitivity advantage of wavelength opponent receptive fields compared to non-wavelength opponent receptive fields and be an important selective advantage of wavelength opponency and color vision.

Adaptation, Ocular↗