Nearby flanking bars degrade letter identification and resolution, a phenomenon known as contour interaction. However, many previous studies found that the relationship between foveal letter identification and flanker separation is non-monotonic, with an upturn in performance at very small target-to-flanker separations. Here, we replicate this observation and show that a similar upturn occurs also for targets presented at 5 deg in the inferior field, if the target-to-flanker separation is sufficiently small. The presence and magnitude of the observed performance upturn depends on the flanking-bar width, being more evident for narrower compared to wider flanking bars. We interpret our results to indicate that neural interactions between nearby contours reduce performance when the target and flanking bars form discrete neural images. At sufficiently small separations, the images of the target and flanking bars can not be distinguished and performance is governed by the contrast of the target in the blended neural image.

• MeSH
• analýza rozptylu MeSH
• citlivost na kontrast fyziologie   MeSH
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• nahuštění v prostoru MeSH
• senioři MeSH
• světelná stimulace MeSH
• vnímání tvaru fyziologie   MeSH
• zraková ostrost fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

SIGNIFICANCE: Both foveal and peripheral contour interactions are based on, as yet, unexplained neural mechanisms. Our results show that, unlike foveal contour interaction, peripheral contour interaction cannot be explained on the basis of the antagonistic structure of neural receptive fields. PURPOSE: Foveal contour interaction is markedly reduced for mesopic compared with photopic targets. This finding is consistent with an explanation based on the antagonistic structure of neural receptive fields. However, no reduction was found for low-luminance targets in the periphery, possibly because the luminances used previously remained substantially above peripheral scotopic detection thresholds. In this study, we compared foveal and peripheral contour interactions for long-wavelength photopic and mesopic targets, which would be expected to significantly elevate the peripheral retinal detection threshold. METHODS: Five normal observers viewed a randomly selected Sloan letter surrounded by four flanking bars at several edge-to-edge separations (min arc). Photopic and mesopic stimuli were viewed foveally and at 6° peripherally through a selective red filter that ensured that mesopic targets were within 1 log unit of detection threshold at both retinal locations. RESULTS: Whereas the magnitude of foveal contour interaction was substantially less at mesopic compared with photopic luminance (20 vs. 46% reduction of percent correct, on average), no significant difference was observed in peripheral contour interaction, which had average mesopic and photopic magnitudes of 38 and 40%. Moreover, confusion matrices representing photopic and mesopic contour interaction differed in the fovea but not in the periphery. The extent of contour interaction did not change with luminance at either retinal location. CONCLUSIONS: Our results indicate that, although the characteristics of foveal contour interaction can be accounted for by the antagonistic structure of neural receptive fields, the same mechanism is not compatible with the characteristics of peripheral contour interaction.

• MeSH
• dospělí MeSH
• fovea centralis fyziologie   MeSH
• lidé MeSH
• senzorické prahy fyziologie   MeSH
• světlo MeSH
• vidění barevné fyziologie   MeSH
• vnímání tvaru fyziologie   MeSH
• zraková pole fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

SIGNIFICANCE: Contour interaction describes an impairment of visual acuity produced by nearby flanking features, which exerts a significant impact in many clinical tests of visual acuity. Our results indicate that the magnitude of interaction depends either on the flanker contrast energy (i.e., the product of flanker contrast and width) or the flanker contrast alone, depending on the contrast energy of the flankers. PURPOSE: The discrimination of acuity targets is impaired by the presence of nearby flanking contours, a phenomenon known as contour interaction. METHODS: In this study, we measured percent correct identification for threshold size, high-contrast Sloan letters at the fovea and at 5° in the inferior visual field for different combinations of flanking-bar width, and Weber contrast corresponding to specific fixed values of contrast energy (width × contrast, in %-min arc). RESULTS: For flanking bars with low-contrast energy, contour interaction exhibited no systematic dependence on the flanking-bar width. However, when the flanking bars had higher contrast energy, narrower high-contrast bars produced significantly greater contour interaction than wider bars of lower contrast. CONCLUSIONS: The results are consistent with the interpretation that contour interaction depends primarily on the contrast energy of flanking contours when their contrast energy is low. As the contrast energy of the flanking contours increases, the magnitude of contour interaction depends on the flanker contrast. For high-contrast flanking contours, the magnitude of contour interaction saturates when the width of the flanking contours is approximately 20% of letter size.

• MeSH
• citlivost na kontrast fyziologie   MeSH
• dospělí MeSH
• fovea centralis MeSH
• lidé středního věku MeSH
• lidé MeSH
• senioři MeSH
• vnímání tvaru fyziologie   MeSH
• zraková ostrost fyziologie   MeSH
• zraková pole fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The role of rodent hippocampus has been intensively studied in different cognitive tasks. However, its role in discrimination of objects remains controversial due to conflicting findings. We tested whether the number and type of features available for the identification of objects might affect the strategy (hippocampal-independent vs. hippocampal-dependent) that rats adopt to solve object discrimination tasks. We trained rats to discriminate 2D visual objects presented on a computer screen. The objects were defined either by their shape only or by multiple-features (a combination of filling pattern and brightness in addition to the shape). Our data showed that objects displayed as simple geometric shapes are not discriminated by trained rats after their hippocampi had been bilaterally inactivated by the GABAA-agonist muscimol. On the other hand, objects containing a specific combination of non-geometric features in addition to the shape are discriminated even without the hippocampus. Our results suggest that the involvement of the hippocampus in visual object discrimination depends on the abundance of object's features.

• MeSH
• agonisté receptorů GABA-A farmakologie   MeSH
• chování zvířat účinky léků   fyziologie   MeSH
• diskriminační učení účinky léků   fyziologie   MeSH
• generalizace (psychologie) účinky léků   fyziologie   MeSH
• hipokampus účinky léků   fyziologie   MeSH
• krysa rodu rattus MeSH
• muscimol farmakologie   MeSH
• operantní podmiňování účinky léků   fyziologie   MeSH
• potkani Long-Evans MeSH
• rozpoznávání obrazu účinky léků   fyziologie   MeSH
• vnímání tvaru účinky léků   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We tested whether eye color influences perception of trustworthiness. Facial photographs of 40 female and 40 male students were rated for perceived trustworthiness. Eye color had a significant effect, the brown-eyed faces being perceived as more trustworthy than the blue-eyed ones. Geometric morphometrics, however, revealed significant correlations between eye color and face shape. Thus, face shape likewise had a significant effect on perceived trustworthiness but only for male faces, the effect for female faces not being significant. To determine whether perception of trustworthiness was being influenced primarily by eye color or by face shape, we recolored the eyes on the same male facial photos and repeated the test procedure. Eye color now had no effect on perceived trustworthiness. We concluded that although the brown-eyed faces were perceived as more trustworthy than the blue-eyed ones, it was not brown eye color per se that caused the stronger perception of trustworthiness but rather the facial features associated with brown eyes.

• MeSH
• barva očí fyziologie   MeSH
• dospělí MeSH
• důvěra * MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• obličej MeSH
• vnímání tvaru fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Contrary to other tasks (free viewing, recognition, visual search), participants often fail to recognize repetition of trials in multiple object tracking (MOT). This study examines the intra- and interindividual variability of eye movements in repeated MOT trials along with the adherence of eye movements to the previously described strategies. I collected eye movement data from 20 subjects during 64 MOT trials at slow speed (5°/s). Half of the trials were repeated four times, and the remaining trials were unique. I measured the variability of eye-movement patterns during repeated trials using normalized scanpath saliency extended to the temporal domain. People tended to make similar eye movements during repeated presentations (with no or vague feeling of repetition) and the interindividual similarity remained at the same level over time. Several strategies (centroid strategy and its variants) were compared with data and they accounted for 48.8% to 54.3% of eye-movement variability, which was less then variability explained by other peoples' eye movements (68.6%). The results show that the observed intra- and interindividual similarity of eye movements is only partly explained by the current models.

• MeSH
• lidé MeSH
• mladý dospělý MeSH
• sakadické oční pohyby fyziologie   MeSH
• světelná stimulace MeSH
• vnímání prostoru fyziologie   MeSH
• vnímání tvaru fyziologie   MeSH
• Check Tag
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Prostorové chování zvířat i člověka zahrnuje komplexní systém kognitivních schopností, které vykazují vysokou evoluční homogenitu. V navigaci rozlišujeme zejména egocentrické procesy (relativní k vlastní poloze) a allocentrické procesy (orientované vůči externím objektům). Ke studiu navigace často slouží úlohy původně vytvořené pro zvířata (zejména potkany). Dnes nejznámější prostorovou úlohou je navigace na skrytý cíl v Morrisově vodním bludišti. Méně známý je pak Test vyhýbání se místu na rotující aréně. Pro testování lidí byly vytvořeny zejména virtuální verze těchto prostorových úloh. Sledování aktivity nebo důsledku lokálního poškození mozkových oblastí během navigace v těchto úlohách pomohlo objasnit neuronální koreláty prostorové kognice. Tyto poznatky vedly také k využití prostorových úloh při stanovení kognitivního deficitu u schizofrenie i schizofrenii podobného chování u zvířat. Výsledky těchto studií naznačují, že budoucí klinické využití virtuálních prostorových testů může být velice slibné.

The spatial behavior of animals and humans involves a complex system of cognitive abilities, which show high evolutionary homog eneity. In particular, we distinguish egocentric navigation processes (relative to one's own position) and allocentric processes (oriented towards external objects). To study navigation in humans, spatial cognition tasks originally created for animals (especially rats) are usually u sed. Today the most famous orientation task is the navigation to the hidden goal in Morris water maze. Less known is the avoidance test on the rota ting arena. Vir- tual versions of these spatial tasks have been created to test the navigation in humans. Observing the neuronal activity using imaging methods and observing the effects of local brain damage during navigation tasks have helped clarify the neuronal correlates of spatial cognition. These findings also led to the usage of these spatial tasks in evaluation of cognitive deficits in schizophrenia and schizophrenia-li ke behavior in ani- mals. Results of these studies suggest that future clinical use of virtual spatial tests could be very promising.

• Klíčová slova
• vyhýbání se místu na rotující aréně, test hledání skrytého cíle, kognitivní deficit,
• MeSH
• financování organizované MeSH
• kognice fyziologie   MeSH
• kognitivní poruchy diagnóza   etiologie   MeSH
• krátkodobá paměť fyziologie   MeSH
• lidé MeSH
• Morrisovo vodní bludiště MeSH
• mozek fyziologie   patofyziologie   MeSH
• neurofyziologie MeSH
• neuropsychologické testy normy   MeSH
• orientace fyziologie   MeSH
• počítačová simulace trendy   využití   MeSH
• podněty MeSH
• prostorové chování fyziologie   MeSH
• psychologické modely MeSH
• psychomotorický výkon MeSH
• reakční čas MeSH
• schizofrenie (psychologie) MeSH
• schizofrenie diagnóza   patofyziologie   MeSH
• učení vyhýbat se fyziologie   MeSH
• vnímání prostoru fyziologie   MeSH
• vnímání tvaru fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• přehledy MeSH

In earlier experiments we have demonstrated that macaque monkeys (Macaca mulatta) are able to use abstract visual stimuli presented on a computer screen to make spatial choices in the real environment. In those experiments a touch board ("response space") was directly connected to the computer screen ("virtual space"). The goal of the present experiment was to find out whether macaque monkeys are able: (1) To make spatial choices in a response space which is completely separated from the screen where the stimuli (designed as representation of the response space) are presented. (2) To make spatial choices based on visual stimuli representing the configuration of the response space which are rotated with respect to this response space. The monkeys were trained to choose one of the nine "touch holes" on a transparent touch panel situated beside a computer monitor on which the visual stimuli were presented. The visual stimuli were designed as an abstract representation of the response space: the rewarded position was shown as a bright circle situated at a certain position in the rectangle representing the contours of the touch panel. At first, the monkeys were trained with non-rotated spatial stimuli. After this initial training, the visual stimuli were gradually rotated by 20 degrees in each step. In the last phase, the stimulus was suddenly rotated in the opposite direction by 60 degrees in one step. The results of the experiment suggest that the monkeys are able to use successfully abstract stimuli from one spatial frame for spatial choices in another frame. Effective use of the stimuli after their rotation suggested that the monkeys perceived the stimuli as a representation of the configuration of the touch holes in the real space, not only as different geometrical patterns without configuration information.

• MeSH
• diskriminační učení fyziologie   MeSH
• hmat fyziologie   MeSH
• Macaca mulatta MeSH
• operantní podmiňování fyziologie   MeSH
• orientace fyziologie   MeSH
• reakční čas fyziologie   MeSH
• rotace MeSH
• rozpoznávání obrazu fyziologie   MeSH
• světelná stimulace metody   MeSH
• vnímání prostoru fyziologie   MeSH
• vnímání tvaru fyziologie   MeSH
• výběrové chování fyziologie   MeSH
• zraková percepce fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH

OBJECTIVES: The objective was to make a contribution to deepening the knowledge of the etiopathogenesis of ADHD. DESIGN: In an association study design, an analysis of polymorphisms of selected genes was conducted in 119 hyperkinetic boys and a control group of boys, aged 7-13. Furthermore several psychologically determined subgroups were identified. A connection between psychological functions (endophenotypes) and genes were looked for. RESULTS: There was a statistically significant difference found in allelic and genotype frequencies of the TaqI A polymorphism of the DRD2 gene. The frequency of the allele A1 in hyperkinetic boys and the control subjects was 0.26 and 0.15, respectively (p<0.003). A statistically significant occurrence of atypical genotypes (8/10, 7/10 and 10/11) of the DAT1 gene was also found in hyperkinetic boys and a connection between the M235 polymorphism of the angiotensinogene gene and the positive family history of psychiatric illness was found in probands (p=0.031). Significant correlations between the results of some neuropsychological tests and genes for neuro-/immunomodulators (IL-6, TNF-alpha) and the gene for the brain-derived neurotrophic factor (BDNF) were found. CONCLUSION: The study showed a statistically significant prevalence of A1 allele of the DRD gene in the hyperkinetic group. We also found a significantly higher incidence of atypical DAT genotypes in the hyperkinetic group. Furthermore we found significant connections with particular gene polymorphisms which may hypothetically represent a neurodevelopmental risk factor in the etiopathogenesis of the disorder (IL-2, IL-6, TNF-alpha, BDNF). We further found a connection of the M235 polymorphism of the AGT (angiotensinogene) gene to positive family history of psychiatric illness (p=0.031). As for cognitive characteristics, we identified three subtypes with different cognitive performance profiles. This finding shows interindividual variability of cognitive style in the group of hyperkinetic boys.

• MeSH
• biologické markery MeSH
• diskriminace (psychologie) fyziologie   MeSH
• dítě MeSH
• fenotyp MeSH
• financování organizované MeSH
• genetické markery MeSH
• genotyp MeSH
• hyperkinetická porucha epidemiologie   genetika   metabolismus   MeSH
• lidé MeSH
• methylfenidát terapeutické užití   MeSH
• mladiství MeSH
• neuropsychologické testy MeSH
• polymorfismus genetický genetika   MeSH
• pozornost fyziologie   účinky léků   MeSH
• psychiatrické posuzovací škály MeSH
• psychomotorický výkon fyziologie   účinky léků   MeSH
• receptory dopaminu D2 genetika   MeSH
• stimulanty centrálního nervového systému terapeutické užití   MeSH
• vnímání tvaru fyziologie   MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• Geografické názvy
• Česká republika MeSH