**2. Cortical organization of the processes of visual gnosis**

functions within the broad framework of typical child development. The pre-school period is sensational to many of the higher psychic functions, which explains the author's interest in it. The rapid rates of genetically determined neurophysiological changes in children are the cause of the heterochronic nature of mental development and its individual variations. The main regularity of the period is the emergence of a wide range of new psychic qualities (intellectual, sensorimotor, linguistic and behavioral) resulting from the complex interaction of biological factors and the social requirements of the environment. Individual rates and partial deficits of neuropsychic development in childhood are one of the main goals of diagnostics as

Indications of delay in pre-literacy skills (both verbal and non-verbal) are predictors of the likely development of specific learning disabilities (specific dyslexia), one of the most prevalent school-age syndromes with increasing incidence rates. The question of his etiology and neuropsychological determinants is still open. The most common manifestations of dyslexia are associated with a disorder in phonological processes, as it is assumed that pre-school phonological skills predict future reading skills [1–3]. At the same time, a number of authors [4–11] maintain the thesis of the leading influence on the difficulties in reading the violations in visual processes (visual search and scanning tasks, selective visual attention, visuospatial attention and visual memory). There are also those who highlight the role of motor difficulties on the academic problems of children [12, 13]. Separate developments examine the symptoms of dyslexia as a result of complex sensorimotor disorders in combination with phonological deficits [14–16]. Data from longitudinal neurobiology studies of children with typical and atypical reading support the thesis of non-typical brain maturation, the features of which refer to the preliterate stage [17]. Some authors [18] pay special attention to persistent silent reading disabilities in primary school pupils, linking them to the complex influence of deficiencies in lexical-grammatical operations, difficulties in non-verbal visual perceptions and

We maintain the view [19] that dyslexia is more accurately conceptualized as a complex interaction of different risk and protective factors, and each of these factors can vary across different individuals with dyslexia. It may be that inefficient auditory and phonological neural systems cause reading difficulties in one individual with dyslexia, but another individual may struggle as a result of predominant visual-orthographic integration problems. Literary analysis of the problem summarizes the following facts of the current research: the core neurobiological cause of dyslexia is still not fully understood; at-risk pre-readers display reliable left temporo-parietal and occipito-temporal differences and early connectivity problems fit

The prognostic value of neuropsychological diagnostics in childhood allows the early application of therapeutic strategies tailored to the nature and mechanisms of developmental deficits. Since non-verbal forms of visual gnosis have the earliest debut in childhood development, the dynamics of their formation can be seen as one of the neurophysiological prerequisites for school readiness. This is most relevant to the functioning of complex gnostic operations associated with the identification of visual stimuli in difficult conditions. Their ontogenetic aspects are poorly developed from a neuropsychological point of view, which explains the

need for a careful analysis of their condition during the pre-school period.

they form the group of children at academic risk.

24 Prefrontal Cortex

limited volume of iconic memory.

with a multifactorial theory of dyslexia [20].

Visual gnosis is a high mental function with very rapid development in early and pre-school age. It is one of the most sensitive indicators in the assessment of child development, and the deficits in its formation lead to specific problems in learning [21, 22]. The operation of visual gnosis has traditionally been associated with cortical associative posterior visual areas and in particular with the operation of both visual streams, vertical and dorsal. They start from the primary visual cortex (V1) and are a continuation of parvocellular (P-type cells) and magnocellular (M-type cells) pathways that bind ganglion cells of the retina with the striate cortex [23]. The ventral tract reaches the temporal-occipital zone, also called "What?" zone, and the dorsal is directed toward the parietal-temporal zone, labeled as "Where?" zone. The dorsal stream serves the analysis of visual motion and visual control of action. The ventral stream is involved in the perception of the visual world and the recognition of objects. In recent years, neuroimaging data identify the prefrontal cortex as a place to integrate visual information processed by the dorsal and ventral flow. This is supported by visual object recognition studies using degraded visual stimuli [24].

Neuropsychological studies traditionally suggest that visual object perception involves several processing stages. Most classical models distinguish between visual identification in the perception stage, which processes presented objects, and the memory stage, which verifies the resulting perceptual representations against representations stored in memory. The perception stage involves part-based analysis and analysis of global forms (feature extraction, segmentation and shape analysis). The memory stage perceptual information is matched to each form stored in memory, which includes memory about the form of an object, its semantic properties and its name [25]. The authors note that subtle perceptual deficits can produce naming problems, even when there is good access to associated semantic knowledge. Contemporary neuroimaging studies indicate that involvement of the right medial occipitotemporal region in the perceptual stage is consistent with the established role of this region in visual object recognition. On the other hand, the memory stage was characterized by the involvement of the posterior part of the rostral medial frontal cortex. It is assumed that this part of the frontal cortex is likely to be relevant in the monitoring process for the confirmation of recognition [24]. Depending on the nature of the stimuli and the cognitive tasks, visual recognition is performed with the participation of various types of memory related to the activity of various neural systems [26]. When recognizing known objects, the modality-specific cortex fields are mainly involved, whereas in difficult-to-recognize stimuli, processes rely on longterm memory information and are implemented with the participation of executive functions.

To explain deficiencies in dyslexia, Levashov [27] develops a model of visual perception. According to the model, with each eye fixation on a particular stimulus, the visual system decides three basic tasks sequentially: builds a map of areas of attention; analyzes familiar objects in them; visually decodes the visible scene; and makes spatial analysis of the objects. The right- and left-hemispheres process differently each input image by sharing results only when solving specific and complex tasks. Processes of attention during performance are related to the dorsal part of the parietal cortex, which suggests that it manages the parameter of so-called "caution."

Visual analysis in difficult conditions (recognition of imposed shapes and incomplete images) is only possible in a time-shared hemisphere interaction from left to right, where the same object is analyzed first on the left and then on the right hemisphere. Levashov suggests the following possible scheme of this interaction in the resolution of visual tasks:

Event-related potential studies of children with a typical development show significant differences in the system of perception of visual information before and after age 5 [32, 33]. It is found that at earlier stages the visual perception processes have diffuse characters, since similar reactive and configuration event-related potentials are recorded in all caudal regions. This explains the difficulties of the children in tasks to integrate signs and reproduce the overall images of objects [34]. After 5 years of age, a process of structuring and lateralization of visual perception processes begins. This is evidenced by differences in reactivity to individual components of event-related potentials in the projection and associative visual areas of the cortex. The data show an increasing specialization of post-center associative departments in the processing of complex visual stimuli, which improves analysis and discrimination of

The Dynamic Maturation Process of the Brain Structures, Visual System and Their Connections…

http://dx.doi.org/10.5772/intechopen.79169

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In the period of 5–6 years, changes in the structural organization of neuronal ensembles in the caudal cerebral regions result in a qualitatively new functional organization of visual perception [35]. In children aged 6–7 years, in the realization of visual gnosis are included structures of the frontal partition, which is the beginning of its intellectualization. The identification of difficult-to-verbalize stimuli is associated with greater reactivity of structures from the temporal and occipital parts. When recognizing stimuli with a simple verbal formulation,

Dorsolateral prefrontal cortex is a high regulatory center and plays an important role in manipulating visual information. The insufficient maturity of the dorsolateral mechanisms during this period explains the weak reactivity of the negative wave, reflecting the cognitive component of visual recognition. The limited involvement of the prefrontal cortex in the analysis of incomplete images suggests a poor development of the regulatory component of perception during pre-school age. New research suggests that the complex of P200-N250 waves in the visual cortex, which is considered to be key in recognizing signs, shows a significant increase in the caudal and precentral cortical divisions after 7–8 years of age [36, 37]. In adults, it is most expressed in the post-temporal parts, which are part of the ventral visual

Neurophysiological studies in complicated perceptual conditions of children show a leading activity of the occipital segments and a lack of significant increase in event-related potentials in the post-temporal regions [38, 39]. It is also stressed that at the age of 5–6 years, components of event-related potentials in the prefrontal cortex are not recorded. According to some authors [35], the low efficiency of fragmented image identification in this period is due to both the immaturity of the prefrontal cortex and the deficiencies in the functioning of the visual system. The low level of recognition under conditions of perceptual deficit is explained by the underdevelopment of regulatory mechanisms and insufficient involvement of the ventral visual system. In the period of 7–8 years, the role of the ventral visual system increases; this corresponds to the morphological data for significant transformations in the neuronal organization of the posterior temporal areas [39]. There is currently no unified opinion on the mechanisms of recognizing incomplete images in children. According to neurophysiological data in the period of pre-school and early school age in their brain organization there are both similarities and differences. Similarities refer to prefrontal cortex involvement in early stages of the analysis of complex visual stimuli.

features when forms and building standards for complex images are compared.

the reactivity is shifted to the frontal lobe.

system and play a major role in recognizing fragmented images.


Through studies with event-related potentials in identifying hierarchical visual stimuli [28], two types of recognition are distinguished—local and global. Local-level recognition is related to the activity of the inferior temporal and prefrontal cortex of the right hemisphere and leads to an assessment of the sensory qualities of the stimuli. At the global-level recognition, the activity of the parietal cortex of the right hemisphere is guided by the inclusion of mechanisms of early sensory selection. Global perception is supposed to be related to the operation of the dorsal visual system and the spatial analysis of the objects. In contrast, perception on a local level (ventral visual system) is directed to the analysis of the elements and properties of the objects. According to some authors [29] of the initial stages of visual perception, the processes are not sufficiently lateralized. They become such at the higher levels of visual analysis when stimulus processing acquires asymmetric organization.

In recent years, the role of feedback on the functioning of cognitive processes has been increasingly discussed. The data show feedback between secondary and primary vision fields and demonstrate the modulation action of the top-down mechanism [30, 31]. Reverse connections are assumed to stimulate the activity and spatio-temporal dynamics of large groups of neurons associated with the integration of visual information.
