Biomedical subjects

J J Kulikowski

Publications and source records attributed to J J Kulikowski.

At least 19 recordsLinked to original sources

PubMed1992

The effects of lesions of area V4 on the visual abilities of macaques: colour categorization.

Monkeys with V4 lesions and unoperated controls were tested behaviourally for their perception of the colour categories red, green, blue and yellow. As expected, the monkeys with V4 lesions took longer to acquire the colour discriminations. However, the pattern of learning was the same in the two groups of animals. Both the lesioned and the control animals made more errors when the stimuli to be discriminated belonged to the same colour category than when they belonged to different categories and thus showed normal colour categorization. The results suggest that monkeys with V4 lesions perceive the colour spectrum according to the same fundamental perceptual categories as normal monkeys and humans, and thus support the view that, in the colour domain, the four basic perceptual categories are constructed by chromatic mechanisms operating earlier than visual area V4.

Animals↗

PubMed1992

The effects of V4 lesions on the visual abilities of macaques: shape discrimination.

Monkeys with bilateral ablation of cortical visual area V4 were compared with unoperated controls for their ability to relearn postoperatively a series of preoperatively acquired two-choice visual discrimination problems. The animals with V4 lesions were impaired on relearning to discriminate between different shapes, and discrimination between identical shapes presented at different orientations was also impaired. Some of the deficits were consistent with disrupting the input to inferotemporal cortex, but discrimination of a subset of the stimuli is known to be unaffected by inferotemporal cortex lesions and could not be explained in the same way. To clarify the nature of the deficit, and to test the hypothesis that shapes differing in orientation are analyzed in the occipitoparietal processing pathway, animals with V4 lesions were also compared to normals on their ability to acquire a version of the landmark task. The V4 animals performed as well as the control animals on this task. The results suggest that V4 is important for the shape discrimination abilities that survive inferotemporal cortex lesions. The role of V4 in shape analysis is discussed in the light of recent evidence that V4 neurones are modulated by visual attention.

Animals↗

PubMed1992

Binocular chromatic rivalry and single vision.

Depth perception is known to be impaired for chromatic equiluminant patterns. To investigate this phenomenon I have compared the effects of binocularly presented stimuli in the form of stripes, which contain only luminance information with similarly presented stimuli which contain only chromatic information. Observations of the reported percepts for the two conditions demonstrate that mechanisms of colour vision can impede stereopsis based on binocular fusion when the chromatic stripes are at, or even near, equiluminance, provided that their saturation is high. This observation is consistent with inhibitory interactions within the chromatic-sensitive neuronal groupings in the visual cortex.

Color Perception↗

PubMed1991

The visual defect in multiple sclerosis and optic neuritis. A combined psychophysical and electrophysiological investigation.

Chromatic and achromatic visual function were investigated using psychophysical and evoked potential techniques in 32 patients with multiple sclerosis (MS) or optic neuritis. There was no evidence for either chromatic or achromatic vision being selectively damaged. There was, however, some evidence that demyelination of the optic nerve causes a visual defect in which the transmission of high temporal frequencies is imparied. In some patients either a red or blue deficit was evident, but overall there was no evidence of a wavelength specific colour vision defect in our patient group. Reduction of chromatic sensitivity as determined psychophysically had a statistically significant correlation with the amplitude and latency of the chromatic visual evoked potential.

Adult↗

PubMed1990

Wavelength discrimination at detection threshold.

The experiments that we report aim to elucidate the linkage between cone outputs and color sensation. This is investigated by measuring wavelength discrimination between stimuli at threshold levels of detection. Stimuli are large spots (0.75 deg) presented on a white background. A 2 x 2 alternate forced choice method is used to measure simultaneously the detection of different wavelengths and discrimination between them. This method reveals at least four distinguishable colors, indicating the presence of four different sets of mechanisms at threshold. These are associated with the color sensations of orange, pale yellow, green, and blue. There is also evidence for a fifth imperfectly distinguished color (violet) in the shortest wavelength region. Results show that the boundaries between the distinguishable colors have little variation in their spectral positions. This is compatible with the presence of fixed perceptual boundaries in the spectrum dividing the different types of detection mechanism. The correspondence of the spectral locations of the distinguishable colors to the cone opponent responses revealed in the spectral sensitivity function suggests that these color sensations are postreceptoral in origin, arising from different combinations of the three cone outputs.

Calibration↗

PubMed1979