DYNAMICS OF THE COMPELEX FORMS OF VISUAL PERCEPTION IN CHILDREN OF PRE-SCHOOL AGE (A NEUROPSYCHOLOGICAL ANALYSIS)

Вовед: Експерименталните податоци за децата од предучилишна возраст сведочат за определувачката улога на аудитивните и визуелните процеси за подоцнежните вештини за читање, па затоа истражувањето на комплексните форми на визуелната перцепција на оваа возраст е дијагностички важно. Цели: Основна цел на ова истражување е проценка на сензитивниот период за невербалните перцептивни операции кај децата од предучилишна возраст и одредување субгрупа со ниски резултати за невербална перцепција. Методологија: Динамиката на визуелната перцепција (визуелно спознавање) кај децата со типичен развој беше тестирана со адаптирана верзија на тестот PoppelreuterGhent Test за сегрегација заснована на слики. Вкупниот број на предмети што се преклопуваат е 33, групирани според нивото на тежината. Децата добиваат од секоја група предмети одделно во последователни секвенции и треба да го издвојат и именуваат предметот. 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.


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.
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.

Моментална состојба Current problems
Последнава деценија детската невропсихологија бележи рапиден развој на Запад, за In the last decades, the children"s neuropsychology marks a rapid development in the 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 (1)(2)(3)(4).
Other existing theories claim that the two types of sensory perceptionauditory and visualare 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 (7)(8)(9)(10).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 diffi-  (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 magnocellulardorsal (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 magnocellular-dorsal (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 identifycationventral (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 hemisphereto 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  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.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.

Mетодологија Method
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). Verbal-perceptive exchangesnaming of a functionally close object from the same semantic category (for example "hammer" is replaced with "axe") -3 points;  Perceptively close mistakesnaming of an object from another semantic category, which has common features ("bucket" -"bin") -2 points;  Perceptively distant mistakesnaming 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 secondtowards 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 80in 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.

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.4 represents the summarized results and the basic effects of the independent factors on the functioning of the operations of за визуелно спознавање при визуелна пренатрупаност кај возрасниот период од 4 до 6 години.Од вредностите на F-критериумот и веројатноста за доверба (Р) јасно е дека трите независни фактори возраст (F=35.20;p<0.0001), средина (F=8.66;p<0.000) и пол (F=5.54;p<0.0191) покажуваат статистички значајно влијание на зависната варијабла.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.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.
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).

Дискусија Discussion
Прикажаните 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 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 предметите.Последователно, ова води кон подобрување на процесите за препознавање на стимулансите и нивната когнитивна контрола.Збирните резултати за влијанието на демографскиот фактор врз развојот на гностичките функции се поврзани со подобрата изведба на децата од голем град, додека влијанието на факторот пол е во прилог на побрз невропсихолошки развој кај женскиот пол.Податоците од квантитативната анализа ги потврдуваат заклучоците за позитивна динамика во развојот на визуелното спознавање при визуелна пренатрупаност за предучилишниот период.Најголеми разлики при точна сегрегација на слики што се преклопуваат повторно постојат кај децата од 4 и 5 години.Ова значи подобрување на врската меѓу перцепцијата и вниманието во текот не периодот од петтата година.Претставените податоци коинцидираат со некои морфолошки истражувања за промените во системот на визуелната перцепција по петгодишната возраст, поврзано со значајните промени во структурната организација на невронскиот склоп во каудалните области на мозокот (29).Исто така, меѓу секоја група деца нема доверливи разлики за случаите на точна сегрегација на предметите што се преклопуваат.Такви случаи за 4-годишни деца се евидентни кај 16% од одговорите, а кај децата од 5 и 6 години се двојно помали -8% и 6% соодветно.Иако со возраста стапката на точна сегрегација на предмети што се преклопуваат се зголемува, децата опстојуваат на правење перцептивно блиски и перцептивно далечни грешки (табела 7).Според Akhutina и Puilaeva (30), не постои единствена кореспонденција меѓу видовите грешки и нивните поттикнувачки механизми.Прифатливо е дека перцептивно блиските грешки се должат на слабоста во програмирањето и контролата, како и во дефицитот во визуелното процесирање.Од друга страна, перцептивно далечните и вербалните грешки се објаснуваат со дефицит во левата хемисфера.Како резултат од едно многу големо истражување, авторите прават компаративна анализа на резултати-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 analy- 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.
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.

Table 4 .
Summarized score of the Poppelreuter test as a dependent variable

Table 5 .
Significance of the average scores' differences of the children from each age group

Table 6 .
Significance of the average scores' differences of the children from the three types of settlements