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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↗
PubMed1987

Occipital lobectomies in foetal lambs.

Foetal lambs undergoing unilateral occipital lobectomy have been investigated post-natally with computed tomographic (CT) scans, visual evoked potentials (VEP) recording and histological examination of their brains. Only the lambs operated at about 100th day of gestation have so far had their investigations completed, however, the results in all the lambs suggests that the foetal brain responds to an occipital lobectomy in essentially the same way as the post-natal brain. To date no evidence of regeneration has been found in any of the brains. It seems reasonable to conclude that if the foetal brain responds to lobectomy in the same manner to the post-natal brain, then its response to disease is likely to be similar. If this is so it can be argued that remediable foetal central nervous system abnormalities should be treated as soon as possible, if necessary in utero.

Animals↗
PubMed1986

Space and spatial frequency: analysis and representation in the macaque striate cortex.

Simple cells in the macaque striate cortex were tested with bars, edges and gratings. Spatial frequency tuning curves could be predicted from the spatial profiles plotted with bars and edges and the bandwidth could be evaluated more accurately by computing the mean from measured and predicted tuning curves. The results suggest that the mean relative spatial frequency bandwidth (delta f/fo) is nearly constant and of a moderate value. But at each optimal spatial frequency, cells with different bandwidths (about a factor of two) were recorded. The shapes of spatial response profiles resemble the corresponding spatial and spatial frequency characteristics of line and edge detectors evaluated psychophysically. Among the remaining cell types, concentric cells tend to be tuned to lower spatial frequencies and have broader bandwidths, whereas periodic cells prefer higher spatial frequencies and have narrower bandwidths. Thus the mean relative bandwidth tends to decrease significantly with spatial frequency (as required by a system of patch-by-patch Fourier analysis) only when cells with poor orientation selectivity and the non-linear silent periodic cells are included along with the simple cells. Simple cells, on their own, seem to form a quasi-linear contrast processing system which is more biased towards spatial accuracy than spatial frequency selectivity.

Animals↗
PubMed1984

Are the amplitudes of visual evoked potentials sensitive indices of hangover effects after repeated doses of benzodiazepines?

Here we compared the efficacy of two electrophysiological techniques in detecting hangover effects after repeated administration (five days) of benzodiazepines. Twelve hours after the last ingestion, possible effects on evoked potentials (EPs) of the long- and short-acting benzodiazepines, flurazepam and lormetazepam, were compared here with those of placebo under a double-blind experimental condition. The EPs were recorded from occipital and parietal sites during an active discrimination of two amoeboid shapes and passive viewing of sine-wave grating patterns turned on and off. In the former task, the subject was requested to make a selective response with respect to whether the two shapes appeared the same or different and his reaction times were simultaneously recorded. Neither benzodiazepine influenced the latencies of any of the sensory and late EP components. Flurazepam's long-acting metabolite, N-desalkylflurazepam, reduced the amplitudes of all the EP components suggesting a somewhat general mode of action. This was not the case for lormetazepam. N-desalkylflurazepam reduced the amplitudes of the occipital visual evoked potentials (VEPs) to sine-wave gratings to a greater extent than the amplitudes of the late parietal EPs to amoeboid shapes. This effect did not show any particular preference for either of the subsystems processing pattern and movement information. The amplitudes of the late EP components, such as N200 and P300 waves recorded from parietal sites, were reduced considerably more after flurazepam administration than their counterparts recorded from the occiput. This observation points to the possible existence of at least two separate sources of the N200-P300 complex with different affinities to the N-desalkylflurazepam. The flurazepam-induced amplitude reduction observed for VEPs to gratings may reflect an attenuation in the detectability of both pattern and movement. The attenuation of the late EP amplitudes is possibly a function of several processes, one of which is conceivably the anxiolytic property of flurazepam which lowers the level of the activation state and this in turn is known to contribute to the amplitude size of the N200-P300 complex.

Adult↗
PubMed1984

Neurotoxic effects of acrylamide on rat retinogeniculate fibres.

The common laboratory chemical, acrylamide, causes various clinical effects including dysfunction of the visual system. Previous electrophysiological recordings from the rat lateral geniculate nucleus (LGN) following exposure to acrylamide suggested that X-like cells were selectively disrupted by the neurotoxin. This study examines the possibility that the diameter of the optic tract fibres may underlie their differential susceptibility, but shows that fibres of all sizes are affected by acrylamide intoxication and the results suggest that the selective effect of acrylamide is not due simply to disruption of optic tract fibres.

Acrylamide↗
PubMed1984

Movement detection and spatial phase.

Contrast thresholds for the detection of movement are determined when a sinusoidal grating pattern is shifted in spatial phase. "True" contrast reversal (180 degrees phase shift) is compared with smaller phase shifts for a range of spatial frequencies. An unexpected increase in movement sensitivity is revealed for intermediate spatial frequencies. This effect is confined to those spatial frequencies where interaction between pattern and movement detectors occurs.

Humans↗
PubMed1984

Macaque striate cortex: pattern, movement and colour processing.

Simple cells in the primate visual cortex provide a form of generalized, pre-cognitive mapping of visual scenes. One point in space is represented by several orientation-specific cells capable of signalling both standing contrast and contrast changes in the scene. The arrangement of simple receptive fields (with a few antagonistic subregions) suggest analysis of scenes both in terms of symmetrical and antisymmetrical spatial components (i.e. lines and edges) and spatial-frequency contents. There is no evidence that this analysis is carried out within fixed areas (or patches) since a diversity of receptive field sizes was observed. A chromatic content is probably analysed by a different class of cells with concentric, cone-opponent receptive fields.

Animals↗
PubMed1983

Contribution of two movement detecting mechanisms to central and peripheral vision.

Two mechanisms, one for the detection of fast, and the other for slow movement of a sinusoidal grating are identified, and investigated under central, parafoveal, and peripheral viewing conditions. The fast movement data is considered in terms of the Reichardt model, in which signals from two adjacent inputs are cross-correlated leading to halving of the spatial resolving power for movement detection, compared with that for pattern detection. The mechanism underlying slow movement detection is regarded as being closely related to pattern detection, probably at the single unit level. The characteristics of this mechanism are discussed in the light of recent electrophysiological experiments describing clusters of simple cells in the visual cortex with "directional preference" properties.

Form Perception↗
PubMed1983

Stereotaxic head restraint for chronic and semi-chronic marmoset and macaque monkeys.

A device allowing head holding and stereotaxic manipulations in both small-sized Marmoset and in relatively large Macaca monkeys is described. Its design permits free access to most targets in the visual system and optimizes presentation of visual stimuli in awake-chronic and anaesthetized semi-chronic preparations. Extra-aural attachments to temporal bone are implanted stereotaxically, under anaesthesia, on both sides of the skull. This provides means for stereotaxic head-holding which minimizes discomfort to the animal. Maintenance of stereotaxic precision over long periods of time, possibility of realignment and use of one device for various monkey species are special features of the method.

Animals↗
PubMed1983

Changes in spatial resolution for pattern and movement detection in clinical cases.

A simple and relatively fast method was used to evaluate visual performance: gratings of sinusoidal luminance profile, generated on the face of an oscilloscope, were reversed in contrast at a rate of 2 Hz. Under these conditions the patients could set separate contrast thresholds for seeing either the structure of a grating or its apparent movement. The grating resolution limit (maximum spatial frequency) for each task was determined by extrapolation from thresholds measured at several spatial frequencies. The resulting ratios of pattern/movement resolution limits (P:M) are usually between 1.6 and 2 for normals and for patients with pathological changes located distally (probably prior to the chiasma). On the other hand in patients suspected of multiple sclerosis the P:M ratios were reduced to below 1.3. It is considered that such results may suggest a central site for the damage, although they do not exclude pre-chiasmal defects which may occur simultaneously during the acute stages of the disease.

Adult↗
PubMed1983

Flash and pattern VEPs: examples of cases of hysterical amblyopia and provoked visual impairment (Uhthoff's sign).

The diagnostic application of averaged visual evoked potentials (VEPs) is illustrated in the investigation of hysterical amblyopia and multiple sclerosis. Averaged VEPs elicited either by a flash of light or a presentation of a grating lasting 100 ms were recorded from the occiput of patients. All the VEPs in hysterical amblyopia were normal. In multiple sclerosis the flash VEPs looked normal for both eyes, whereas the VEPs elicited by grating (2 and 5 c/deg) showed an increase in the latency of the first positive wave, again for both eyes. After physical exercise the VEPs from the right eye were dramatically reduced in amplitude (Uhthoff's sign).

Adolescent↗
PubMed1982

Theory of spatial position and spatial frequency relations in the receptive fields of simple cells in the visual cortex.

Striate cells showing linear spatial summation obey very general mathematical inequalities relating the size of their receptive fields to the corresponding spatial frequency and orientation tuning characteristics. The experimental data show that, in the preferred direction of stimulus motion, the spatial response profiles of cells in the simple family are well described by the mathematical form of Gabor elementary signals. The product of the uncertainties in signaling spatial position (delta x) and spatial frequency (delta f) has, therefore, a theoretical minimum value of delta x delta f = 1/2. We examine the implications that these conclusions have for the relationship between the spatial response profiles of simple cells and the characteristics of their spatial frequency tuning curves. Examples of the spatial frequency tuning curves and their associated spatial response profiles are discussed and illustrated. The advantages for the operation of the visual system of different relationships between the spatial response profiles and the characteristics of the spatial frequency tuning curves are examined. Two examples are discussed in detail, one system having a constant receptive field size and the other a constant bandwidth.

Animals↗
PubMed1982

Silent periodic cells in the cat striate cortex.

A class of neurons called silent periodic cells, having properties intermediate between those in the simple and complex families, has been discriminated in the cat striate cortex. Silent periodic cells have relatively small receptive fields, a low spontaneous activity (i.e. relatively silent) and a preference for relatively slow stimulus velocities (less than 3 degrees/sec). In addition they give a mixed on/off response to a stationary flashing bar over virtually the whole of the receptive field with usually somewhat stronger on responses in some locations and stronger off responses in others (partial phase sensitivity). The most characteristic properties of these cells are, however, found in their responses to gratings, namely the nonlinearity manifested by the absence of a null point to a stationary flashing grating, a spatial periodicity revealed by a clearly modulated discharge to drifting gratings of medium and high spatial frequency and, finally, a very sharp spatial frequency tuning curve with a half-sensitivity bandwidth between 0.5 and 0.95 octave, i.e. narrower than that of simple cells whose bandwidths are usually above 1 octave. Silent periodic cells resemble B-cells that have been described in other studies.

Animals↗