In the present visual psychophysical study, the Oppel-Kundt and and Müller-Lyer illusion magnitudes were measured separately (by single figures) and in combination (by two patterns superposed spatially). Data for 30 subjects revealed extensive variability both for the separate and combined illusion strength. Nevertheless, the effect of addition of the perceived length distortions was established. The combined illusions were significantly stronger than the separate ones. Dynamics of the misperceptions summation was studied by varying length of the Müller-Lyer wings in the superposed stimuli. According to the experimental data obtained, the two misperceptions in length occurred and combined into sensory response varying in dependence on the spatial parameters of the superposed stimuli and on the individual experimental accomplishment. The data supported an explanation for the origin of the filled/unfilled illusion: overestimate of a filled interval length developed due to the spatiotemporal integration along a continuous excitation path elicited by the real or imaginary contours of the filling.

Perceptual estimates of spatial dimensions of visual objects depend on their shape and surface attributes. The present psychophysical study emphasizes two main contributors to the Oppel-Kundt illusion: the outline of the filled space and the mode of filling. In past experiments, both factors have been considered significant. Our experiments were performed by using combined stimuli of the Oppel-Kundt figures and supplementary objects situated within the empty intervals of the figures. Line segments, empty and filled rectangles, blurred contours, and grey and color images were used for the supplementary stimuli role. The experimental data demonstrated an innate property of the objects to balance the illusion of distance if they were placed within the Oppel-Kundt figure and to create an illusion of extent when compared with an empty space interval. Both the balance magnitude and the induced illusion strength varied depending on the objects' spatial structure. The supplementary objects showed a tendency to differ from each other by their functional capacity and were ranked from lowest to highest: a line segment, a solid bar with a blurred outline, a contour of a rectangle, a solid fill rectangle, greyscale patterns, and color pictures. The experimental findings provided support for an explanation of the Oppel-Kundt illusion in terms of the spatial-temporal summation of excitations representing the object outline and surface attributes at the lower cortical levels of the visual system. Along with the facts already established in current literature, the experimental data gave rise to the assumption that any visual object could appear larger than its occupied area, and that the Oppel-Kundt illusion could become a separate case in the common sensory phenomenon of object size illusion.

The "centroid" explanation of the Müller-Lyer and similar illusions of extent supposes the perceptual positional shifts of the stimulus terminators in direction of the centers-of-masses of adjacent contextual flanks. In the present study, the validity of the assumption was tested in psychophysical examination of illusory figures comprising the Müller-Lyer wings or arcs of a circle as the contextual objects. In experiments, the illusion magnitude changes evoked by the tilting of stimulus flanks have been measured. A good resemblance between the experimental data and theoretical predictions was obtained that strongly supports the idea of local positional shifts and serves in favor of "centroid" explanation of illusions investigated.

Šiame straipsnyje aprašomi eksperimentai, kuriuose stebėtojų prašoma pastumti vieną iš trijų pagrindinių stimulo dėmelių į vietą, tenkinančią reikalavimą: 1) trys dėmelės išsirikiuoja viena linija arba 2) išsidėsto stačiu kampu, arba 3) abu Brentano tipo iliuzinės figūros intervalai tampa vienodo ilgio. Suvokimo klaidų dydis matuojamas kaip atstumo tarp dėmelių ir šalia jų esančių papildomų objektų funkcijos. Gautos šių objektų sukeliamų skirtingų geometrinių iliuzijų kiekybinės charakteristikos. Eksperimentų duomenys interpretuojami, remiantis lokalios jaudinimų integracijos ir svorio centro postūmio samprata. Pasiūlytos atitinkamos analitinės funkcijos gana tiksliai aproksimuoja eksperimentines kreives. Išskaičiuotieji erdviniai lokaliosios integracijos parametrai yra tiesiškai susiję su bendruoju stimulo dydžiu. Pagrindiniai žodžiai: tiesumo, stataus kampo ir ilgio iliuzijos, papildomi šalia esantys objektai, lokalioji integracija, svorio centro postūmis.Influence of Distracter on Perceived Stimulus Length and Angle SizeAlgis Bertulis, Aleksandr Bulatov, Arūnas Bielevičius SummaryThis study describes experiments in which subjects adjusted the spatial positions of spots in three different kinds of basic stimuli in order to best perceive a required spatial property: 1) vernier alignment in a three-spot line arrangement, 2) orthogonality in a right-angled triangle constructed of three spots, or 3) length equality in a Brentano type figure. The magnitudes of the perceptual errors were measured as functions of the distance between the spots and flanking objects placed in close proximity to the spot stimuli. Quantitative characteristics of the strengths of the different illusions were obtained with the flanking objects placed at varying extents of spatial separation. The data were interpreted in terms of centroid biases caused by local integration processes. An appropriate analytical description of the experimental data was proposed, and a good correspondence between it and the data was obtained. The calculated spatial parameters of the local lateral integration showed a linear dependence on the stimulus size. Key words: illusions of alignment, right angle and linear extent, contextual flanks, local integration, centroid bias.

Background: Genetic variations, localized in the 3′ untranslated region (UTR) in mitogen-activated protein kinase (MAPK) pathway-related genes, may alter the transcription and impact the pathogenesis of laryngeal squamous cell carcinoma (LSCC). The present study investigated the associations of single-nucleotide polymorphisms (SNP), localized in the 3′UTR) of the KRAS, NRAS, and MAPK1 genes with LSCC risk and clinicopathological features. Methods: Genomic DNA and clinical data were collected from 327 adult men with LSCC. The control group was formed from 333 healthy men. Genotyping of the SNPs was performed using TaqMan SNP genotyping assays. Five KRAS, NRAS, and MAPK1 polymorphisms were analyzed. All studied genotypes were in Hardy–Weinberg equilibrium and had the same allele distribution as the 1000 Genomes project Phase 3 dataset for the European population. Results: Significant associations of the studied SNPs with reduced LSCC risk were observed between NRAS rs14804 major genotype CC. Significant associations of the studied SNPs with clinicopathologic variables were also observed between NRAS rs14804 minor T allele and advanced tumor stage and positive lymph node status. SNP of MAPK1 rs9340 was associated with distant metastasis. Moreover, haplotype analysis of two KRAS SNPs rs712 and rs7973450 revealed that TG haplotype was associated with positive lymph node status in LSCC patients. Conclusions: According to the present study, 3′UTR SNP in the NRAS and MAPK1 genes may contribute to the identifications of patients at higher risk of LSCC lymph node and distant metastasis development.