Dynamics of the Compelex Forms of Visual Perception in Children of Pre-School Age (A Neuropsychological Analysis)

Dynamics of the Compelex Forms of Visual Perception in Children of Pre-School Age (A... Introduction: Experimental data in preschool aged children proves the determining role of the auditory and visual processes for future reading skills, therefore the investigation of complex forms of visual perception in this age period is diagnostically important. Objectives: Basic aim of the research is assessment of the sensitive period for the non-verbal perceptive operations in preschool aged children, and determination of subgroup with low results for non-verbal perception. Methods: The dynamics of the visual perception (visual gnosis) in typically developing children were tested with an adapted version of the Poppelreuter-Ghent Test for figure-ground segregation. The total number of overlapping objects is 33, grouped according to the level of difficulty. The children are given a group of objects separately in a following sequence and they should segregate and name the objects. Coresponding address: Neli VASILEVA Sofia University "St. Kliment Ohridski", Sofia, Bulgaria E-mail: vasnel@abv.bg JOURNAL OF SPECIAL EDUCATION AND REHABILITATION : 365 . , 4, 5 6 , . , . 5- , 4- (p<0.000009) (p<0.001650). (p<0.000926) (p<0.000700). (F = 1,346, p<0.019). , 25% . : 4 6 . Poppelreuter's test . : , PoppelreuterGhent Test, , , , Results: A number of 365 typically developing children without diagnosis of visual disorders and without corrected visus took part in the research. All children, aged 4, 5, and 6 from three different settlements attend state nursery schools and have Bulgarian as a mother tongue. A three-factor dispersion analysis was held to define the statistical significance of the independent factors age, gender and settlement. The research's data define the 5 year olds as sensitive about the dynamics of the complex forms of visual perception, compared to the four year old children (p<0.000009) and the six year old children (p<0.001650). The influence of the demographic factor is engaged with the significantly better results of the children from the big town compared to the capital (p<0.000926) and small town (p<0.000700). The influence of the gender as a factor is due to the better functioning of the non-verbal perceptive operations in the females (F = 1,346, p<0.019). According to the additional analysis, 25% of the children at the age of six demonstrate a low rating of the complex forms of non-verbal visual gnosis that could be reviewed as risk for developing dyslexia. Conclusion: In the age period 4 ­ 6, there is a process of dynamic maturation of the righthemispheric structures of the ventral visual system, leading to substantial improvement of the abilities for discrimination of objects in visual crowding. Poppelreuter's test allows an objective assessment of the state of the non-verbal perceptive abilities in pre-school age and could be used in the diagnostics of predictors for dyslexia. Keywords: visual gnosis in complex environment, Poppelreuter-Ghent Test, figureground segregation, dorsal and ventral visual pathways, preschool age, developmental dyslexia Current problems In the last decades, the children's neuropsychology marks a rapid development in the MEDICAL TREATMENT . ( ), . . . , , ( ), (1­4). - - (5). (6). ( ) (7­10). ( ) . , ( ) , , . Gori & Facoetti (11), Western, likewise in the Eastern schools. Most frequent objects of neuropsychological researches are the different categories of children with learning difficulties (developmental dyslexia), and the aim of the studies is to compose their neuropsychological profiles. The last mentioned require various combinations of basic and additive deficits in groups of primary neuropsychological functions. One of the bestinvestigated categories is the dyslexic syndrome. Data, focusing upon predictors for developmental dyslexia, broadly discuss the difficulties in phonological awareness and rapid automatized naming (or rapid naming), also identified as underlying indicators for future difficulties for mastering of reading (1­4). Other existing theories claim that the two types of sensory perception ­ auditory and visual are deficient in cases of developmental dyslexia (5). Experimental data in preschool aged children proves the determining role of the auditory and visual processes for future reading skills in early school age (6). Some authors conclude a significant connection between the visual processing (visual discrimination) and successful training in reading (7­10). These are grounds to look at the deficits in the functioning of the visual gnosis(representing processes of classification and identification of visual objects) in typically developing preschool aged children as a possible neuropsychological predictor for dyslexic symptoms. The development of the complex forms of visual gnosis are taken into consideration, which are engaged in the processes of discerning and identifying real objects in complex environment (overlapping objects or line drawings occult by noise). They are also related to the functioning of the visual system, which as a complex neuronal apparatus binds the peripheral divisions of the vision with the specialized cortex areas, which create a complete image. According to Gori&Facoetti (11), a number of authors determine excessive visual crowding as a visual deficit, associated with developmental dyslexia. The visual crowding creates diffiJOURNAL OF SPECIAL EDUCATION AND REHABILITATION , . , . , . Facoetti . (12) , - . Franceschini . (13). - . - (14) ­ () . , . Gori . (15) - . Levashov (16) . ­ () (). , ,,-", - , ,,-". , . , , . , , , culties when recognizing objects, surrounded by similar ones. Although crowding is usually related to the peripheral vision, it could be modulated by attentional processes. Based on an experimental research Facoetti et al. (12) summarize that in the pre-reading stage the childrenat risk for dyslexiademonstrate significant deficits in visual-spatial attention. Analogical data from alongitudinal study report Franceschiniet al. (13). They conclude that visual spatial attention in preschoolers specifically predicts future reading acquisition. The magnocellular ­ dorsal (M - D) theory (14) stems from the observation that a high percentage of reading disabled children are impaired in the specific visual M ­ D pathway. Over the last years, this is used as an explanation for developmental dyslexia. Gori et al. (15) summarize experimental data, according to which there is a causal relationship between the deficits in the functioning of the visual magnocellular­dorsal (MD) pathway and the developmental dyslexia. Levashov (16) also raises a hypothesis, which explains the difficulties in reading with disorders in the neurophysiological base of the visual perception. He reviews its connection to functioning of the pathways of visual identifycation ­ ventral (parvucellular) and dorsal (magnucellular), which reaching the cortex form the ventral and dorsal tracts. The ventral tract reaches the temporal-occipital zone, also called "What?" zone, and the dorsal is directed towards the parietal-temporal zone, labelled as "Where?" zone. In the process of visual perception, an asymmetry between the two tracts exists. In the right hemisphere, they are related to the zones of spatial analysis and visual memory, and in the left hemisphere ­ to the zone for somatognosis and the zone responsible for reading and writing. The functioning of the right hemisphere is connected to spatial analysis, spatial orientation under visual control, recognition and memorizing of complex objects (including faces), copying of tri-dimensional objects, and segregation of MEDICAL TREATMENT ( ), . , . Ivanickiy . (17) - , . , . , Federmeier Kutas (18) . ( ), ( ). , , , . , . (19, 20). . . Akhutina Puilaeva (21) 5 7 . 56 overlapping objects or incomplete figures. On the other hand, the left hemisphere is dominant for recognition and reading of letters and words. According to Ivanickiy et al. (17) the investigations of the nonverbal visual gnosis give valuable information for the functioning of the dorso-temporal and occipital areas, and for the interaction between the perception and attention processes. The gradual functional matureness of the perception and attention leads to age-related specifics of the connections between them, resulting in perception awareness. Based on electrophysiological testing with event related potentials, Federmeier and Kutas (18) conclude that the left hemisphere uses contextual information to prepare for the visual analysis of the stimuli. The results support the authors' thesis that the left hemisphere actively utilizes the "top-down" information to pre-activate the perceptive and semantic features of the stimuli (analytical strategy), whereas the right hemisphere follows the integrative approach (holistic strategy). Up to the present moment, in the framework of child neuropsychology, most common appear to be the investigations of the visual perception, taking into consideration its early debut in the child development. The visual perception has a leading role in the cognitive functioning, securing the child's contact with the environment and the spatial orientation. It is accepted as one of the most sensitive markers when assessing the child's development that is why its deficits lead to specific learning problems (19, 20). Significant for the study of the visual perception are the ontogenetic researches. The heterochronic matureness of the brain structures in the ontogenesis allows the outlining of the stages and dynamics of its formation. Akhutina and Puilaeva (21) quote data according to which in the period 5 ­ 7 years the disorders of the visual gnosis for objects are more explicit in cases of right hemisphere lesions. The symptoms are manifested with difficulties in recognition of realistic objects JOURNAL OF SPECIAL EDUCATION AND REHABILITATION . . . 8 10 11 13 , ( - ) . . Simernitskaya (22) , . ( ). Farber Beteleva (23), , 16-17 . . Petrenko Farber 5- 7- (24). 5­6 . 5- . 6­7 - , 3­4 . 5- and plot pictures with signs for sinister ignorance. Most recognizable are the mistakes in cases of deficits in the work of the dorsal and fronto-temporal areas. Left hemispheric lesions in children in this age range cannot be related to significant disorders on the visual gnosis. In the age periods 8-10 and 11-13, the importance of the left hemisphere (especially of the temporooccipital areas) increases regarding the visual perception. Parallel increases the role of the homo-topic right hemisphere areas responsible for these processes. Simernitskaya (22) registers prominent disorders in the visual gnosis in children with right-hemispheric lesions, whereas lesions in the left hemisphere cause only difficulties in recognition of schematic object images. She concludes that the lesions in the right hemisphere lead mainly to distant exchanges (the named object does not match the one in the image) and to sinister ignorance. According to Farber and Beteleva (23), the child has an inborn right-hemispheric strategy for information processing, while the left-hemispheric one is mastered fully around the age of 16-17. Then the frontal cortex is actively included in the concluding stages of the perception. Petrenko and Farber prove that the period between the ages of 5­7 is connected with intensive maturation of the structures responsible for the analysis of the visual information (24). The significant changes during the ages 5­ 6 in the organization of the neuronal ensembles in the cortex caudal regions become premises for differential processing of the elements of the visual stimuli. Neurophysiology examinations through the method of event-related potentials show significant change in different cortex areas before and after the age of five. In children, aged 6­7 there are discrepancies in the reactivity of the potentials' components from the projecting and associative-visual areas; whereas, in the age period 3­4 similar in configuration event-related potentials are registered from all caudal areas. This explains the more successful segregation of modified MEDICAL TREATMENT . , , , , . Terebova (25) 4­7 - . Levashov Boyeva (26) , 7-9 , , . . , . , . objects from five-year-olds. Additionally, there is a transformation of the eye movements from fixed on details, into tracking the whole object, enabling better summary of the process of visual gnosis. Terebova (25) points out that the formation of the separate components of the visual perception during the age diapason 4­7, progresses unevenly with the visual-spatial component and the constant nature of perception forming last. Levashov and Boyeva (26) test visual discrimination in right-handed and left-handed children, aged 7 ­ 9, and report a better performance of the left-handed children, which is explained with the connection between the leading hand and the right hemisphere. The neuropsychological researches on children usually focus on the early school age and hinder the derivation of principles of the neuropsychological ontogenesis. In this sense, the current experimental research aims to line the tendencies and sensitive periods in the formation of the complex forms of visual gnosis in typically developing pre-school aged children. An additional goal is the specification of a subgroup of normally developing children, who express critically low results for visual perception, which could be a predictor for future readingdifficulties. Poppelreuter-Ghent . , . ( ) , , ,,". 58 Method This research uses the Poppelreuter-Ghent Test for segregation of overlapping objects. This current probe investigates the nature of the processing of visual information in the complex environment, since the visual crowding requires a figure-ground segregation. While performing the test the two visual pathways (ventral and dorsal) in the right hemisphere activate, with a prevalence of the ventral pathway, because it is connected to localizing the object and responding to the question "What?" The difficulties in the segregation of the Poppelreuter's figures are usually connected to functional deficits in the occipital area of the right hemisphere, because lack or rejection of JOURNAL OF SPECIAL EDUCATION AND REHABILITATION , (27). , , . . 33 : 5 ( 1), 2 4 ( 2), 5 ( 3), 5 - ( 4). . , . response is mostly among children with faults in the right-hemispheric functions (27). For the demand of naming the segregated object, the temporal areas of the left hemisphere are additionally activated, along with their connections to the occipito-temporal structures in the right hemisphere. The participation of the word changes the perception of the object, since it consolidates its most prominent features. The selection of the testing stimuli is agreeable to the early age of the children and includes familiar objects with growing level of difficulty. The total number of objects is 33: 5 pairs colored overlapping objects (Figure 1), two groups of 4 colored overlapping objects (Figure 2), 5 colored overlapping objects (Figure 3) and two groups of 5 black-and-white overlapping objects (Figure 4). The investigation is individual and the answers are put in a separate protocol. The children are given each group of objects separately in a following sequence and should segregate and name the objects. 1 / Figure 1. 2 / Figure 2. 3 / Figure 3. : ­ 5 ; ( ­ 4 / Figure 4. Assessment criteria: Correct naming of an object ­ 5 points; Recognition of the object with hesitation in naming it (exchange the object name with its functional use ­ for instance instead of `kettle' ­ `the thing we pour tea with') ­ 4 points; MEDICAL TREATMENT , ) ­ 4 ; - ­ ( , ,," ,,") ­ 3 ; ­ (,,'"­ ,,") ­ 2 ; ­ (,," ­ ,,") ­ 1 ; ( ) ­ 0 . , , . , : . , . 365 . / . : 4- (116 ), 5- (128 ) 6 (121 ). , ­ 195 (1.300.000 ), 90 (80.000 ) 80 (11.000 ). 173 192 . -, . Verbal-perceptive exchanges ­ naming of a functionally close object from the same semantic category (for example `hammer' is replaced with `axe') ­ 3 points; Perceptively close mistakes ­ naming of an object from another semantic category, which has common features (`bucket' ­ `bin') ­ 2 points; Perceptively distant mistakes ­ naming of objects from another category due to incidental association with some of the object's elements (`hedgehog' ­ `sun') ­ 1 point; Misses (fails to see the object) or cannot name it ­ 0 points. The features of the functional system of visual perception are determined by indicators such as accuracy, completeness, volume and time for perception. In this case, volume and accuracy of perception are measured by using two parameters: number of correct answers and typology of the incorrect answers. The first one is related mostly to the statistical analysis of the results, and the second ­ towards their interpretation. 365 typically developing children without diagnosis of visual disorders and without corrected visus took part in the research. All children attend state nursery schools and have Bulgarian as a mother tongue. They form three age groups: 4-year-olds (116 children), 5-yearolds (128 children) and 6- year-olds (121 children). Besides the age factor, the children were separated according to the size of settlement they live in ­ 195 children from the capital (1 300000 inhabitance), 90 living in a big city (80 000 inhabitance)and 80 ­ in a small town (11 000 inhabitance). The proportion according to gender is 173 male and 192 female. The results are operated with a tri-factor dispersion analysis, which has been performed separately for each type of tasks. JOURNAL OF SPECIAL EDUCATION AND REHABILITATION - (F=8,41; p<0.000) . * (F=4.58; p<0.001). , 5- . 1. / Age 4 / 4 years 5 / 5 years 6 / 6 years 0.000015 0.000011 {1} - 42.209 Results Segregation of two overlapping objects The values of the F-criteria from the dispersion analysis show that only the independent age factor (F=8.41; p<0.000) has a statistically significant influence on the dependent variable for figure-ground segregation. There is a significant impact of the paired interaction Age*Settlement (F=4.58; p<0.001). The profile of the age factor shows a graduate growth in the score for the sub-test, most prominent for the 5year-olds. Table 1. Significance of the average scores' differences from segregation of two overlapping objects {2} - 44.409 0.000015 0.338075 {3} - 44.877 0.000011 0.338075 Duncan , 5 6 . ( 1). , . , . (F=31.271; p<0.000), (F=19.04; p<0.000) (F=8.22; p<0.004). 4- 6- Duncan's test establishes statistically significant differences between each two means, except from the means of the children aged 5 and 6. The intermediate values for these ages are relatively close (table 1). Segregation of four overlapping objects The test requires a continuous segregation of two pairs consisting of four coloured overlapping objects each, which leads to visual crowding and significant complication of the visual attention. The results from the disperse analysis review that the higher the visual stimuli's difficulty, the higher the number of independent factors with statistically significant impact on the average scores. Statistically significant impact on the dependent variable have the factors age (F=31.271; p<0.000), settlement (F=19.04; p<0.000) and gender (F=8.22; p<0.004). The profile of the age factor shows a gradual increase of the average score with a direction from 4- to 6-year-olds. The increase of the MEDICAL TREATMENT . 5-. , Duncan ( 2). 2. / Age 4 / 4 years 5 / 5 years 6 / 6 years 0.000009 0.000011 {1} - 26.600 intermediate values of the segregation of four overlapping objects is again most obvious for the five-year-olds. However, the Duncan's test reveals statistically significant differences between each two age groups (table 2). Table 2. Significance of the average scores' differences from segregation of four overlapping objects {2} - 31.764 0.000009 0.000500 {3} - 34.844 0.000011 0.000500 (F=20.34; p<0.000) (F=4.27; p<0.0126), (F=2.686; p<0.031). . 5 . ( 3). 3. / Age 4 / 4 years 5 / 5 years 6 / 6 years 0.000009 0.000011 {1} - 47.183 Segregation of five overlapping objects The results from the disperse analysis of the sub-test for segregation of five overlapping objects, show a statistically significant influence upon the dependent variable of the age (F=20.34; p<0.000) and settlement (F=4.27; p<0.0126) factors, as well as on their interaction (F=2.686; p<0.031). The profile of the age factor shows a positive dynamics of the nonverbal gnosis operations. The increase of the average scores again is highest for the age of five. The difference between each two means is statistically significant (table 3). Table 3. Significance of the average scores' differences from segregation of five overlapping objects {2} - 54.441 0.000009 0.038430 {3} - 57.090 0.000011 0.038430 Consolidated results from the test for overlapping objects segregation Table 4 represents the summarized results and the basic effects of the independent factors on the functioning of the operations of JOURNAL OF SPECIAL EDUCATION AND REHABILITATION 4 6 . F- () (F=35.20; p<0.0001), (F=8.66; p<0.000) (F=5.54; p<0.0191) . 4. Poppelreuter SS / Intercept / Age / Settlement / Gender * / Age*Settlement * / Age*Gender * / Settlement*Gender ** / *Settlement*Gender / Error 5043232 18963 4664 1493 2572 81 877 2690 93189 visual gnosis in visual crowding in the age period 4 ­ 6. From the values of the F-criteria and the confidence probability (P) it is clear that the three independent factors age (F=35.20; p<0.0001), settlement (F=8.66; p<0.000) and gender (F=5.54; p<0.0191) have statistically significant influence on the dependent variable. Table 4. Summarized score of the Poppelreuter test as a dependent variable / Degr. of - Freedom 1 2 2 1 4 2 2 4 346 MS 5043232 9482 2332 1493 643 41 438 673 269 F 1 724.86 35.20 8.66 5.54 2.39 0.15 1.63 2.50 p 0.000000 0.0000001 0.000214 0.019118 0.050837 0.8602 1 0.197979 0.042586 Poppelreuter 4- 6- , . Duncan ( 5). 5. / Age 4 / 4 years 5 / years 6 / 6 years 0.000009 0.000011 {1} - 115.64 The profile of the age factor shows increase in the average score of the Poppelreuter test directed from the age of 4 towards the age of 6, where the average score is highest. Duncan's test proves statistically significant the difference between each two age-related means (table 5). Table 5. Significance of the average scores' differences of the children from each age group {2} - 130.17 0.000009 0.001650 {3} - 136.80 0.000011 0.001650 . The influence of the demographic factor on the development of the gnosis functions becomes obvious from the higher summarized score of the children from the big city. The scores of the children from the capital MEDICAL TREATMENT . ( 6). (F = 1,346, p = 0.019). 6. / Settlement / capital / big city / small town 0.000926 0.981106 {1} ­ 125.87 and the small town are lower and analogical. Statistically significant appears to be only the difference between the mean of the children from the big city and the means of the other two groups of children (table 6). The summarized results for the influence of the gender factor on the results for overlapping objects segregation support the thesis for better achievements of the female compared to males (F = 1.346, p = 0.019). Table 6. Significance of the average scores' differences of the children from the three types of settlements {2} ­ 133.63 0.000926 0.000700 {3} ­ 125.92 0.981106 0.000700 7. Poppelreuter / Age / Correctly recognized / Perceptively close Table 7. Distribution of the types of answers to the Poppelreuter test between the children from all ages / Perceptively distant / Pseudognositic / Unrecognized / Sum of the incorrect answers 38% 29% 24% 4 / 4 years 5 / 5 years 6 / 6 years 62% 71% 76% 11% 12% 10% 10% 9% 7% 1% 1% 0,5% 16% 8% 6% 7 . 4 6- . Table 7 represents the percentage distribution of the correct answers and of the types of wrong answers of the children from each age group. This allows a quantitative analysis of the results and supports the data for positive dynamics of the nonverbal visual gnosis for the age period 4 ­ 6. . 4- 64 Discussion The represented data suggest better management with the sub-test for segregation of two overlapping objects. Only the children aged four demonstrate low results on this JOURNAL OF SPECIAL EDUCATION AND REHABILITATION . , . , . . , . 5- . , (24). . , , . . ( ) , . . . , sub-test. Usually they could segregate the objects, but make mistakes in their correct identification and verbalization. The sub-test for segregation of four overlaping objects leads to visual crowding, which obscures the visual attention of the children. This explains the difficulties in object segregation and the significant differences between the results of each two age groups. The results reveal a positive dynamics in the formation of the visual gnosis processes, which is supported by the proportional increase of the segregated objects with age. The significant growth of the average scores of the 5-year-olds, confirms the role of this age period for the quantitative and qualitative changes in the neurophysiological organization of the visual tracts and for the general neuropsychological functioning. This is supported by the data for significant changes during this age period in the organization of nerve ensembles in the caudal cortex areas, establishing grounds for differential processing of the visual stimuli (24). The influence of the settlement factor on the state of the visual gnosis, when segregating four objects, is also interesting. On this subtest, the highest score were the children from the big city, whereas the children from the capital have the lowest mean. Between the children from each two settlements, there are legitimate differences. This data confirms the thesis for the influence of the social factors (family environment and upbringing methods) on the neuropsychological development and functioning in childhood age, which sets the need for additional comparative demographic researches. The influence of the gender factor is evident from the relatively higher average scores of the females. The results support the thesis for the overtaking neuropsychological development and better functioning of the holistic right-hemispheric processing of the visual information in female children. When it comes to segregation of five overlapping objects, the highest results are MEDICAL TREATMENT . . 4 6 . , . - , . Poppelreuter 4 6 , . , . . . , 5 6- . 6 . Farber Petrenko (28), , , - performed by the five-year-olds. The legitimacy of the differences between the means speak for their proportional increase with age. This could be viewed as a marker for accelerated development of the ventral visual system in the age period 4 - 6. This period appears sensitive for the complex forms of visual gnosis, connected with processes for figure-ground segregation in visual crowding. The skills improvement for accurate recognition of objects in visual crowded is connected with active formation of horizontal connections between the occipito-temporal and frontal cortex areas, where the last one express a controlling function. The summary of the results on the Poppelreuter test show an increase of the ability for synthesis of elements from the overlapping objects in the age period 4 - 6, mostly evident for the five-year-olds. The existence of significant differences between each age period is a proof for positive dynamics in the functioning of the structures from the postemporal and occipital areas of the right hemisphere, as well as for improvement of the performance of the ventral visual system.The data are supporting the previously quoted statements for the role of the visual motor functions in testing visual objects. The higher results of the five-yearolds in figure-ground segregation are most probably due to the fixations of the sight towards the most significant features of the object. All the same, the confidence differences in the results of the 5- and 6-year-olds speak for improvement of the tracking eye movements as a marker for the consoledation of the processes for visual gnosis. This explains the small amount of mistakes done by children aged six in figure-ground segregation. The represented data are supported by research made by Farber and Petrenko (28), which proves activation, correlating with age, of the structures from the ventral visual system responsible for the modal-specific features of the objects. Consequently, this leads to improvement of the processes for recognition of the stimuli and their cognitive JOURNAL OF SPECIAL EDUCATION AND REHABILITATION . , . , . . 4 5 . . , (29). , . 4- 16% , 5 6 - 8% 6% . , ( 7). Akhutina Puilaeva (30), . , . , . , control. The summarized results for the influence of the demographic factor on the development of the gnosis functions are connected with better performance of the children from the big city, whereas the influence of the gender factor proves the faster neuropsychological development in females. The data from the quantitative analysis confirm the conclusion for the positive dynamics in the development of the visual gnosis in visual crowding for the preschool age period. The biggest differences in correct segregation of overlapping figures are again among the children ages 4 and 5. This means improvement of the connection between the perceptions and attention during the period of the fifth year. The represented data coincide with some morphological investigations for changes in the system of the visual perception after the age of five, connected with significant changes in the structural organization of the neuronal ensembles in the caudal brain areas (29). All the same, between each group of children confidence differences for the cases of correct segregation of overlaping objects are not present. This is completed by the percentage distribution of the nonsegregated overlapping objects. Such cases for the children aged 4 are evident in 16% of the answers, whereas for the children aged 5 and 6 they are twice less ­ 8% and 6% respectively. Although with the age the rate of correctly segregated overlapping objects increases, the children persist on making perceptively close and perceptively distant mistakes (table 7). According to Akhutina and Puilaeva (30), a single correspondence between the type of mistakes and their triggering mechanism does not exist. It is accepted that the perceptively close mistakes are due to weaknesses in the programming and control, as well as to deficits in the visual processing. On the other hand, the perceptively distant and verbal mistakes are explained with left hemisphere deficits. As a result from a huge investigation, the authors make comparative analy67 MEDICAL TREATMENT , Poppelreuter ( ) . , , . Poppelreuter . 6-, , : - 26% , - 49% - 25%. ¼ . Poppelreuter . sis of the results from different probes for visual gnosis, which show that the Poppelreuter test appears to be the most difficult for the children with undeveloped analytical (lefthemispheric) principle of information processing. They conclude that in children with equal level of development, some individual differences are evident, due to the uneven formation of the components of the visual and verbal functions. The additionally outlined age norms for the accomplishment of the Poppelreuter tests show interesting tendencies. It appeared that for the 6-year-olds, who are about to enter school, three subgroups could be defined: leading group ­ 26% of the researched children, medium group ­ 49% and behind group ­ 25%. This means that ¼ of the future students express significant weaknesses in the abilities of visual discrimination in cases of visual crowding. The unsatisfactory development of the complex forms of visual perception could be viewed as a predictor for future reading difficulties and proves the diagnostic and prognostic validity of the Poppelreuter probe for the pre-school age period. 4 - 6 , . , . , . Conclusion The analysis of the represented data shows that for the age period 4 ­ 6 there is a process of dynamic maturation of the righthemispheric structures of the ventral visual system, leading to substantial improvement of the abilities for visual discrimination of objects in visual crowding. The use of the prognostic abilities of the elaborated, for the children's neuropsychology diagnostic tool is very important, since they allow early registering of the cases of delayed development in the frameworks of the broad children norm. This could respond to one of the leading tendencies in the developmental neuroscience, connected with early prevention of future reading difficulties. JOURNAL OF SPECIAL EDUCATION AND REHABILITATION . / http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Special Education and Rehabilitation de Gruyter

Dynamics of the Compelex Forms of Visual Perception in Children of Pre-School Age (A Neuropsychological Analysis)

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