[Acuity and hyperacuity for pupils of 11-17 years old].

Estimations of hyperacuity and visual acuity (VA) have been compared in schoolchildren aged 11-17 years with normal vision. VA was measured using Landolt Cs and Tumbling Es. Hyperacuity was measured by vernier stimuli. Acuity estimations depended on the test stimuli. They were in 1.1 times over for Landolt Cs than for Tumbling Es. Hyperacuity estimations exceeded VA in 1.25-4.1 times. They were almost twice as high among pupils of 16 years compared to 13-year-olds, in contrast to estimates of VA, which practically did not change with age. Binocular VA was significantly higher monocular VA in 1.05 times regardless of age. The ratio between the binocular and monocular hyperacuity estimates for thirteen years pupils in average was equal to 1.9, while for sixteen years pupils--1.2. We discuss the contribution of binocular vision in the development of mechanisms of VA and hyperacuity in ontogenesis and the difference between these mechanisms.

[Age related size invariance in perception of illusory and fragmented contours].

We investigated invariant perception to sizes of images. Observers were schoolmates of 7-17 years and adults. Two types of stimuli were used: fragmented line drawing of common objects and discs with deleted sectors, which represented illusory Kanizsa contours when discs were in particular positions. In experiments with fragmented images, we found an improvement in image recognition with observers' age, increasing up to 13-14 years. The probability of recognition of fragmented line drawings increased significantly with decreasing stimulus size for children of 7-12 years, indicating that size invariance at recognition for fragmented line drawings was absent in these children. However, size invariance was found for observers of 13-17 years and for adults in this task. At Kanizsa illusion appearance, the ratio of the separation between discs and disc diameter was smaller when we used larger disc diameters. This ratio increased with increasing age of observers. Obtained results provide evidence for the absence of size invariance when perceiving the Kanizsa illusion in our experimental conditions.

[Chondroblastoma].

Chondroblastom, benign cartilage tissue neoplasm, accounts for 1% of all bone tumors. It is encountered in any skeletal bones mainly in persons aged 10 and 25 years. Morphologically, it is represented as large homogenous cells--well-defined oval polygonal chondroblasts with a fine eosinophilic cytoplasm, and a round-to-oval nucleus. Cartilaginous portions of chondroblastoma form lobular structures. The tumor always comprises single-to-multiple multinucleate giant cells. The pathognomonic sign of chondroblastoma is intercellular reticular basophilically stained calcifications as a mesh. Mitotic cells, rather than abnormal ones, are present. There are cases of primary malignant chondroblastomas.

The threshold signal:noise ratio in the perception of fragmented figures.

Perception thresholds were measured for fragmented outline figures (the Gollin test). A new approach to the question of the perception of incomplete images was developed. In this approach, figure fragmentation consisted of masking with multiplicative texture-like noise--this interference was termed "invisible" masking. The first series of studies established that the "similarity" between the amplitude-frequency spectra of test figures and "invisible" masks, expressed as a linear correlation coefficient, had significant effects on the recognition thresholds of these figures. The second series of experiments showed that progressing formation of the figures was accompanied by increases in the correlation between their spatial-frequency characteristics and the corresponding characteristics of the incomplete figure, while the correlation with the "invisible" mask decreased. It is suggested that the ratio of the correlation coefficients, characterizing the "similarity" of the fragmented figure with the intact figure and the "invisible" mask, corresponds to the signal:noise ratio. The psychophysical recognition threshold for figures for naive subjects not familiar with the test image alphabet was reached after the particular level of fragmentation at which this ratio was unity.

[The seasonal variability of Drosophila population according to the individual asymmetry].

The natural Drosophila population is characterized by the presence of directional (DA) and fluctuating (FA) asymmetry of individuals. It was found that genotype has an effect on DA-level. FA evaluated in spring, summer and autumn periods had its maximum value in summer period. Genetically determined seasonal decrease in size of individuals was accompanied with increase in their FA. The structure of FA population variability is defined by genotypes of individuals. The phenotype and genotype structures of Drosophila population were investigated by FA of the individuals. There was regrouping of lineages number within of each frequency class in period from spring to autumn. Investigating central frequency class with least FA values in spring to summer period we observed the decrease in number of lineages for all traits with the exception of sternoupleral bristles (SB). At the same time the increase in number of lineages in the central and extreme frequency class with maximal FA values of sternoupleral bristles (SB). At the same time the increase in number of lineages in the central and extreme frequency class with maximal FA values of lines is observed. The number of lineages in the central frequency class of genotype structure is prevailing to all traits, without dependence on season. Individuals with rather high FA value acquire advantages in summer period whereas the individuals with low FA--in spring and autumn periods. Annual dynamics of FA is defined by this population parameters reorganization. The reasons of seasonal change of FA are discussed.

[Spatial selectivity of vestibular receptive fields of cerebellar Purkinje cells towards the orientation of angle accelerations]. / Prostranstvennaia izbiratel'nost' vestibuliarnykh retseptivnykh polei kletok Purkin'e mozzhechka k orientatsii uglovykh uskorenii.

Using microcaloric stimulation of semicircular canals of the frog vestibular apparatus parameters of orientation sensitivity of the receptive fields of the cerebellum Purkinje cells towards angle accelerations were studied. A change of this sensitivity depending on the value of acting angle acceleration was shown.

[Effect of centrifugal force on neck nystagmus in pigeons]. / Vliianie tsentrobezhnoi sily na sheinyi nistagm u golubei

The neck nystagmus and its changes under the influence of an otolith stimulus--centrifugal force were studied in pigeons. The results show that centrifugal forces exert a dynamic effect on the nystagmus.

[Signal/noise ratio at the visual recognition threshold of incomplete figures]. / Porogovoe otnoshenie signal/shum pri vospriiatii fragmentirovannykh figur.

We measured recognition thresholds of incomplete figure perception (the Gollin test). This test we regarded as a visual masking problem. Digital image processing permits us to measure the spatial properties and spatial frequency spectrum of the absent part of the image as the mask. Using a noise paradigm, we have measured the signal/noise ratio for Incomplete Figure. Recognition was worse with better spectral "similarity" between the figure and the "invisible" mask. At threshold, the spectrum of the fragmented image was equally similar to that of the "invisible" mask and complete image. We think the recognition thresholds for Gollin stimuli reflect the signal/noise ratio.