Age-related size invariance in perception of illusory and fragmented contours

We investigated invariant perception to sizes of images. Observers were secondary school students aged 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 observer’s age, increasing up to 13–14 years. The probability of recognition of fragmented line drawings increased significantly with decreasing stimulus size for children aged 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 aged 7–12 years and for adults in this task. Upon the 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. The obtained results provide evidence for the absence of size invariance when perceiving the Kanizsa illusion under our experimental conditions.     

Neurophysiological mechanisms of recognition fragmented images in 5 to 6-year-old children

Behavioral indices and ERP parameters were analyzed in 5-6 years old children who were shown a previously unseen set of fragmented drawings of familiar objects. Within this set, each object was represented by a series of drawings of different degree of fragmentation. It is found that children of 5-6, when compared to 7-8 years old children, are capable to recognize less fragmented drawings. In these children, no increase was found in N350-400 prefrontal negativity and late positive complex, otherwise a typical feature of mature recognition involving executive control. A comparison of ERP for recognized vs. unrecognized stimuli showed a significant increase in P300 and N400 amplitude over the right occipital area. A key feature of children of this age is a lack of significant difference between ERP to recognized vs. unrecognized stimuli over extrastriatal cortex (T5/T6) which is the crucial structure for recognition of fragmented objects via integration of their sensory features. The data we obtained suggest that both executive control immaturity and insufficient involvement of the ventral visual system constitute a specifics of recognition in children of 5-6.     

Perception of visual image size by school students of different ages

In psychophysical experiments, 209 high school students with normal vision, 8 to 16 years old, were examined to study the perception of visual image sizes. Observers assessed the length of linear arrow-like figures (the Müller-Lyer illusion) or the length of single lines without arrow-like ends. Distortion of line size perception by 17–21% was obtained in the Müller-Lyer illusion independent of the age of observers. Distortion of size perception was absent in the case of estimation of the length of single line segments. The size differentiation thresholds gradually decreased in both cases with increasing age of observers and were correlated with the acuity of vision. For single lines, they were, on average, 1.3 times lower than the thresholds in the Müller-Lyer illusion. The probable mechanisms of the Müller-Lyer illusion are discussed. The experimental results demonstrate stability of illusion for observers aged 8–16 years, which may be connected with preferential contribution of the lower levels of the visual system to the appearance of the illusion.     

Neurophysiological mechanisms of recognition fragmented images by five- to six-year-old children

Behavioral indices and event-related potentials (ERP) were analyzed in five- to six-year-old children who were shown a set of previously unseen fragmented drawings of familiar images. These children recognized less fragmented images than seven- to eight-year-old children. At the age of five to six years, there was no increase in N350–400 prefrontal negativity and slow positive complex, which is characteristic of mature recognition that involves executive control. Comparison of ERP for recognized vs. unrecognized stimuli revealed a significant increase in the P300 and N400 amplitudes in the right occipital area. Note that, in children of this age, there were no significant differences between reactions to recognized and unrecognized images in the lateral extrastriate cortex (T₅/T₆), which is the key structure for recognition of familiar images via integration of their sensory features. Our data suggest that in five- to six-year-old children recognition of fragmented images has specific features determined by immaturity of the executive control and insufficient involvement of the ventral visual system.     

Chondroadherin Fragmentation Mediated by the Protease HTRA1 Distinguishes Human Intervertebral Disc Degeneration from Normal Aging

Chondroadherin, a member of the leucine-rich repeat family, has previously been demonstrated to be fragmented in some juveniles with idiopathic scoliosis. This observation led us to investigate adults with disc degeneration. Immunoblotting analysis demonstrated that non-degenerate discs from three different age groups show no chondroadherin fragmentation. Furthermore, the chondroadherin fragments in adult degenerate disc and the juvenile scoliotic disc were compared via immunoblot analysis and appeared to have a similar size. We then investigated whether or not chondroadherin fragmentation increases with the severity of disc degeneration. Three different samples with different severities were chosen from the same disc, and chondroadherin fragmentation was found to be more abundant with increasing severity of degeneration. This observation led us to the creation of a neoepitope antibody to the cleavage site observed. We then observed that the cleavage site in adult degenerate discs and juvenile scoliotic discs was identical as confirmed by the neoepitope antibody. Consequently, investigation of the protease capable of cleaving chondroadherin at this site was necessary. In vitro digests of disc tissue demonstrated that ADAMTS-4 and -5; cathepsins K, B, and L; and MMP-3, -7, -12, and -13 were incapable of cleavage of chondroadherin at this site and that HTRA1 was indeed the only protease capable. Furthermore, increased protein levels of the processed form of HTRA1 were demonstrated in degenerate disc tissues via immunoblotting. The results suggest that chondroadherin fragmentation can be used as a biomarker to distinguish the processes of disc degeneration from normal aging.     

Analysis of fragmented images perception: local features and global description

Analysis of experimental investigations of the perception of incomplete images is presented. It illustrates two different approaches to work of the brain mechanisms involved: one approach is based on the perception of whole images and another on local informative features. These approaches describe two different mechanisms, which are possibly used by brain systems for incomplete image recognition. Performance on the Gollin test (measuring recognition thresholds for fragmented line drawings of everyday objects and animals) depends upon recognition based on image informational-statistical characteristics. We suggest that recognition thresholds for Gollin stimuli in part reflect the extraction of signal from noise. The brain uses local informative features as an additional source of information about them. We have suggested that fragmented images in the Gollin-test are perceived as whole structures. This structure is compared with a template in memory which is extracted with the help of selective attention mechanism in accordance with a matched filtration model. The Gollin-test is a tool for differential diagnosis of a various forms of cognitive disorders.     

Size Estimates in Ebbinghaus Illusion in Adults and Children of Different Age

Psychophysical experiments were performed with the participation of 297 subjects (adults and 6- to 17-year-old children and adolescents). Perception of the size of a central stimulus surrounded by other stimuli was studied. Subjects had to estimate the size of a circle with a diameter of 22 angular min, which was surrounded by four similar figures with a diameter of either 11 or 44 angular min at a distance of either 11 or 33 angular min. The misperception of the stimulus size was dependent on the subject's age, the distance between the circles, and the size of the flanking circles. The smaller flanking circles located at any distance produced size underestimation in younger children; these circles led to size overestimation in case of their location at a short distance in most adults and adolescents. The larger flanking circles produced underestimation in all age groups, but, in adults, unlike children, this illusion decreased with increasing distance. The illusion mechanism and its possible connection with selective attention are discussed.     

Female-specific wing degeneration is triggered by ecdysteroid in cultures of wing discs from the bagworm moth, Eumeta variegata (Insecta: Lepidoptera, Psychidae)

Female adults of the bagworm moth, Eumeta variegata, are completely wingless; by contrast, the male adults have functional wings. Sex-specific differences in the development of wing discs appear to arise during the 8th (penultimate) larval instar. We have previously found that the wing discs of female E. variegata terminate development and disappear during the prepupal period, whereas the wing discs of males continue to develop fully into adult wings. We have investigated the effects of ecdysteroid (20-hydroxyecdysone, 20E) when cultured with larval wing discs, which are normally attached to the larval integument of both male and female larvae. Male wing discs cultured with 20E undergo a remarkable transformation: the discs undergo apolysis and then differentiation. Female wing discs cultured with 20E also undergo apolysis; however, the disc cells enter apoptosis. We have observed condensed chromatin, fragmented nuclei, and secondary lysosomes in the epithelial cells of these female discs. This report establishes that the reduction of female wing discs arises through apoptotic events triggered by ecdysteroid in vitro.     

Specificity of recognition of fragmented images in seven- to eight-year-old children: Analysis of event-related potentials

The topography and parameters of event-related potentials (ERPs) recorded during the presentation of incomplete images with different fragmentation were analyzed in seven- to eight-year-old children. The degree and mode of the involvement of different cortical zones at different stages of analysis and processing of fragmented images were determined. It was found in children that the prefrontal cortical areas were involved in the recognition of incomplete images in the same way as in adults. Age-related differences manifested themselves in a lower intensity of the slow positive complex in children, reflecting the decision-making and information retention processes required for the preparation of an answer.     

Tenascin in the human intervertebral disc: alterations with aging and disc degeneration

Our objective for this study was to determine the presence and distribution of tenascin in the human intervertebral disc. The tenascins are a family of extracellular matrix proteins with repeated structural domains homologous to epidermal growth factor, fibronectin type III and the fibrinogens. Little is known about the presence of this protein in the disc. Ten normal human discs donated from subjects newborn to 15 years old, 10 control discs from adult donors aged 24-41 years, and 11 surgical disc specimens from patients aged 26-76 years were examined for immunolocalization of tenascin. In young discs, tenascin was localized throughout the annulus; in the nucleus, localization was confined to pericellular matrix. In adult control and degenerating disc specimens, tenascin in the annulus was localized primarily in pericellular matrix regions encircling either single cells or clusters of disc cells; in rare instances localization was more diffuse in the intraterritorial matrix. In young, healthy disc, tenascin was abundant throughout the annulus. In contrast, degenerating discs in adults showed a localization restricted to the pericellular, and rarely, more restricted intraterritorial matrix. These observations indicate that changes in the amount and distribution of tenascin may have a role in disc aging and degeneration, possibly by modulating fibronectin-disc-cell interactions, and causing alterations in the shape of disc cells.     

Functional organization of the brain in the period of preparation for recognizing fragmented images in seven- to eight-year-old children and adults

Functional connectivity between the prefrontal cortex and the temporal and temporo-parieto-occipital cortices in the process of preparing for the recognition of fragmented images were analyzed in adults (n = 26) and seven- to eight-year-old children (n = 20).The evaluations of the imaginary part of the complex-valued coherency for the EEG alpha-rhythm (Jα) were used as an index for the strength of cortico-cortical interactions. The Jα value was analyzed in the following three experimental conditions corresponding to different stages of readiness for visual recognition: (1) nonspecific attention holding in the period preceding a warning stimulus (S1); (2) focused attention in the interval preceding a not-yet-recognized target stimulus (S2) and (3) pretuning preceding a recognized stimulus (S3). Adult subjects tended towards a growing level of functional connectivity in α-rhythm in progressing from attention holding to focused attention preceding the emergence of a target stimulus, but children, on the contrary, demonstrated a decreasing trend. Comparing the Jα values in the subgroups of adults and children who showed the highest recognition scores in the solution of cognitive tasks helped reveal age-specific patterns in the rearrangements of cortico-cortical functional connectivity in α-rhythm in the left and right hemispheres at different stages of readiness for recognizing incomplete images. In adults, the maximal Jα values were found in the left hemisphere in the interval preceding the recognition of a target image. At this stage of pretuning, the Jα values at the leads in the left hemisphere in adults significantly exceeded those in children. The Jα values for the right hemisphere in adults were maximal during focused prestimulus attention when the image was not yet recognized and these values were significantly higher than in children under the same experimental conditions. Children showed maximal Jα values in both hemispheres during nonspecific attention. The specifics of functional connectivity observed between the prefrontal, temporal and temporo-parieto-occipital cortices in seven- to eight-year-old children during functional pretuning to the recognition of fragmented images are considered to reflect the relative immaturity of neurophysiological mechanisms underlying the voluntary attention and working memory in children of this age group.     

Shoot regeneration from petunia leaf discs as a function of explant size,configuration and benzyladenine exposure

The effect of explant size, configuration, and duration of benzyladenine exposure on shoot organogenesis in Petunia x hybrida Ultra Salmon leaf discs was determined. Leaf discs of 13, 10, 8, 5, and 3 mm diameter, and 10 mm with a 5 o4 3 mm hole and 13 mm with an 8 or 5 mm hole were tested. The smallest size and configuration for maximum shoot production and consistency of regeneration was a 10 mm whole disc. This was followed by the 8, 10 with a 3 mm hole, 5, 10 with a 5 mm hole and 3 mm disc respectively. Of all configurations tested, the 13 mm disc and the 13 mm disc with a 5 mm hole produced the most shoots. Exposure of leaf discs to benzyladenine-containing medium for 4 days or less resulted in no shoots being formed. Exposure for 10 days or more induced shoot regeneration on all discs tested. A delay of more than 2 days after excision, before plating on benzyladenine-containing medium, decreased shoot regeneration significantly. The explant configurations tested showed that: the area to cut edge ratio was a good predictor of shoot number for either of the two configurations when considered separately; and there are factors other than area to cut edge ratio involved in relating shoot production to explant configuration and size.Abbreviation BA benzyladenine     

The elongation of the human cervical vertebral column

Cervical vertebral elongation has been studied using serial cephalometric radiographs of 32 children examined regularly from 0.25 to 17 years. Mean vertebral body heights increased rapidly to about 2.5 years and then decelerated except for a spurt at about the age of peak height velocity. There were only small sex differences in vertebral body elongation to 12 years. From then to 15 years, the vertebral body heights in the girls exceeded those in the boys; later this sex difference was reversed. There was no pubertal spurt in disc elongation. The correlation coefficients were negative between vertebral body heights and the heights of adjoining intervertebral discs, e.g., body C3 and disc C3–4, but those between body heights or between disc heights were positive. The heights of adjacent cervical vertebral bodies were correlated more highly than the heights of non-adjacent bodies. There was a similar pattern of differences between correlation coefficients for the heights of adjacent and non-adjacent intervertebral discs.     

Measurement Invariance of the WHODAS 2.0 in a Population-Based Sample of Youth

The World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) is a brief measure of global disability originally developed for adults, which has since been implemented among samples of children and youth. However, evidence of its validity for use among youth, particularly measurement invariance, is lacking. Investigations of measurement invariance assess the extent to which the psychometric properties of observed items in a measure are generalizable across samples. Satisfying the assumption of measurement invariance is critical for any inferences about between-group differences. The objective of this paper was to empirically assess the measurement invariance of the 12-item interview version of the WHODAS 2.0 measure in an epidemiological sample of youth (15 to 17 years) and adults (≥ 18 years) in Canada. Multiple-group confirmatory factor analysis using a categorical variable framework allowed for the sequential testing of increasingly restrictive models to evaluate measurement invariance of the WHODAS 2.0 between adults and youth. Findings provided evidence for full measurement invariance of the WHODAS 2.0 in youth aged 15 to 17 years. The final model fit the data well: χ²(159) = 769.04, p < .001; CFI = 0.950, TLI = 0.958, RMSEA (90% CI) = 0.055 [0.051, 0.059]. Results from this study build on previous work supporting the validity of the WHODAS 2.0. Findings indicate that the WHODAS 2.0 is valid for making substantive comparisons of disability among youth as young as 15 years of age.     

Tactile size discrimination by a California sea lion (Zalophus californianus) using its mystacial vibrissae

The capability of a blindfolded California sea lion (Zalophus californianus) to discriminate diameter differences of circular discs by means of active touch with its mystacial vibrissae was studied. Using a forced choice paradigm the sea lion was required to choose the larger of two simultaneously presented perspex discs. Absolute difference thresholds (D) were determined for 3 standard discs (1.12 cm Ø, 2.52 cm Ø, 8.74 cm Ø) by the psychophysical method of constants. Increasing disc size resulted in an increase in the absolute difference threshold from 0.33 cm for the smallest disc size to 1.55 cm for the largest disc size. The relative difference threshold (Weber fraction) remained approximately constant at a mean value of 0.26. According to a video analysis the sea lion did not move its vibrissae when touching the discs. Instead, it performed precisely controlled lateral head movements, with the touched disc located centrally between the vibrissae of both sides of the muzzle. Since the extent of these head movements was identical at discs to be compared, discs of different size must have led to different degrees of deflection of vibrissae involved in the tactile process, resulting in quantitatively different mechanical stimulations of mechanoreceptors in the follicles. This suggests that the accuracy of the sea lion's size discrimination was determined by the efficiency of two sensory systems: the mechanosensitivity of follicle receptors as well as kinaesthesis.Abbreviations D starting stimulus size - D _i size of the interpolated comparison disc at 75% correct choices - D absolute difference threshold     

The three-dimensional structure of the Z disc in insect supercontracting muscles

Two types of Z disc structure have been reported in insect supercontracting muscle fibres: (i) a perforated Z disc where Z material forms a reticulum and (ii) a fragmented Z disc composed of separate, discrete Z bodies. The use of thick (I μm) sections in conjunction with high voltage electron microscopy can distinguish between these two types while conventional thin sections may lead to misinterpretation of structure. It is shown that in one insect, the crane-fly Tipula, the larval body-wall muscles, for which a fragmented Z disc has been proposed, do in fact have a perforated disc. In the wax moth Galleria, homologous muscle fibres have a similar type of Z disc, a finding which indicates the need for re-examination of other lepidopteran muscles claimed to have fragmented discs. A redefinition of supercontraction is proposed which includes reference to the perforated type of Z disc.     

Spontaneous disc degeneration in the baboon model: magnetic resonance imaging and histopathologic correlation

Degenerative disc disease is a major source of disability in humans. The baboon model is an excellent natural disease model to study comparable human disease, because baboons are relatively large (adult males 20-26 kg, adult females 12-17 kg), long-lived (30-45 years), well defined, easy to use, and closely related to humans. Published investigations with plain radiographs of disc degeneration in baboons indicated vertebral anatomy and changes that were remarkably similar to those seen in humans, and it would be valuable to determine if magnetic resonance imaging (MRI) and histopathologic evaluation would be useful methods for studying the model, as MRI allows multi-planar visualization of tissues without the use of intravenous contrast and it is superior for evaluating disc hydration, annulus tears, and herniations. The thoracolumbar junctions from 47 randomly selected baboons, ranging in age from 2 weeks to 34 years, were evaluated with MRI and histopathology. Excellent correlation with MRI was observed for changes in disc desiccation, height, and age (P < 0.001). The pathologic analysis demonstrated P values of < 0.001 when comparing histopathology with age and MRI results. All severely degenerated discs seen by MRI were in baboons 14 years of age or older.     

Increased IL-17 expression in degenerated human discs and increased production in cultured annulus cells exposed to IL-1ß and TNF-α

Abstract

IL-17 is expressed in a number of tissues including the intervertebral disc, where it exerts strong inflammatory properties. We evaluated IL-17 using immunolocalization in herniated and non-herniated human discs, IL-17 gene expression, and the production of IL-17 by annulus cells cultured in three dimensions in the presence of IL-1ß or TNF-α. There was no difference in the percentage of IL-17 positive cells in annulus or nucleus in herniated vs. non-herniated disc specimens. Molecular studies confirmed expression of IL-17 in disc tissue, with significantly increased expression in more degenerated discs; there was no difference in expression between herniated vs. non-herniated discs. Exposure to IL-1ß or TNF-α resulted in significantly greater production of IL-17. Our findings expand understanding of IL-17 production by disc cells and reveal the importance of non-canonical IL-17 production in the disc. Significantly greater expression of IL-17 in more degenerated discs adds to our understanding of the changes in disc cell function with advancing stages of disc degeneration.     

Development of mechanisms of recognition of fragmented images differing in the degree of fragmentation in children of preschool and primary school ages

Recognition of fragmented images with an increasing number of fragments was studied in children of three age groups (five to six, seven to eight, and nine to ten years of age) to compare the behavioral and neurophysiological parameters of recognition in these groups. The most pronounced changes in effectiveness of recognition were observed when the five- to six-year-old and seven- to eight-year-old children were compared. In the former, recognition was not accompanied by any significant changes in the event-related potentials of the prefrontal cortex or by an increase in N250?C400 (Ncl) in the extrastriate cortex (though it is an important characteristic of the process). However, the amplitude of the N170?C200 component, which reflects analysis and encoding of sensory features, did increase at the age of five to six years. Immaturity of the prefrontal cortex is manifested in a deficiency of the control: these children respond hastily and make numerous mistakes. In seven- to eight-year-old children, recognition is accompanied by an increase in the amplitude of the N100 and N250 components in the prefrontal cortex, whereas the amplitude of the Ncl component increases in the extrastriate cortex. The error rate and recognition threshold are significantly lower in these children than at the age of five to six years. The role of prefrontal cortex is the most pronounced at the age of nine to ten years, which is manifested in the Ncl amplitude and the later phases corresponding to the cognitive recognition. Our results demonstrate qualitative differences in the mechanisms of recognition in children of the preschool and primary school age. At the age of five to six years, recognition is a result of integration of the sensory signs. Beginning from the age of seven to eight years, the prefrontal cortex plays an important role in recognition of the fragmentary images; this brain region is responsible for a search of possible analogues in memory and identification of an object.     

Study of parvocellular and magnocellular visual channels in normal subjects and in patients with psychopathology

We measured susceptibility to the Müller-Lyer illusion in schizophrenic patients and normal observers. The images of the Müller-Lyer figure were digitally filtered in a high-frequency and low-frequency band by wavelet filter. Patients with schizophrenia are more susceptible to Müller-Lyer illusion, than mentally healthy examinees. The images of the Müller-Lyer figure with low spatial frequency were perceived in a similar way by the schizophrenic patients on the initial stage of disease and the control subjects. Patients with schizophrenia were more sensitive to the Müller-Lyer illusion when the image contained only high or medium spatial frequency. Schizophrenic patients in advanced stage were more susceptible to the illusion while presented with all types of images of the Müller-Lyer figure than the control group. It is hypothesized that those differences arise from the mismatch work of the magnocellular and parvocellular systems. It is known that images with the high spatial frequencies are most relevant for the parvocellular visual channels. The magnocellular visual channels are most sensitive to the images with the low spatial frequencies. Thus these findings demonstrate a significant impairment in parvocellular pathway function in patients on initial stage of schizophrenia. The patients on advanced stage of schizophrenia demonstrate impairment of both the parvocellular and magnocellular systems.