ISSUES OF VISUAL ATTENTION AND EXECUTIVE FUNCTIONS IN CHILDREN WITH DYSLEXIA.

Dyslexia is the most common learning disability that affects 10-12% of population. The reading difficulties in dyslexia have neuronal basic and are associated to the problems with brain areas where visual information processing happens, and that are responsible for word analysis and for attention. Visual processing is essential for reading process but there is an ongoing discussion whether attentional deficits in dyslexia plays a role. In the present study we investigated development of visual attention and executive functions in Georgian children with dyslexia. Two groups of children aged between 7-12 years participated in the study: children with dyslexia and age and IQ (general intelligence) match typically developing children. Participants performed visual search task and Wisconsin Card Sorting Test (WCST), and were retested after a year from the first testing. We found no differences in performance (correct responses) of search task between two groups but there were differences in reaction time. Attentional functions improved with getting older in control children, that is confirmed by improvement of reaction time after one year. There were no changes in reaction time in dyslexic children indicating that attentional deficits are not compensated by developmental processes. No correlation was found for any of groups between performances of executive function task and search task. Significant correlation was found between performance of WCST and age of control children, but no correlation between performance of WCST and age of dyslexic children. These results indicate that common development of executive and attentional functions during childhood are different for control and dyslexic children. We conclude that in children with dyslexia ongoing developmental processes in general are slowed down that affects development of attentional and executive functions.

VISUAL PROCESSING IN GEORGIAN CHILDREN WITH NEURODEVELOPMENTAL DISORDERS.

Neurodevelopmental disorders are disabilities that cause impairment in learning, language, or behaviour areas. ADHD and learning disabilities, namely dyslexia have the greatest prevalence among these disorders and very often co-occur together. As visual perception is essential for development of academic abilities, it is very important question whether visual processing is affected in children with neurodevelopmental disorders or not. There are controversial scientific evidences whether visual perceptual deficits are related to neurodevelopmental disorders or not. Here we investigated such aspects of visual processing as visual attention and visual working memory. Three groups of Georgian children participated in our study: children with dyslexia, children having ADHD and dyslexia together and typically developing children. Two types of attentions were evaluated with two different tasks: selective attention using visual search task and sustained attention using Go/NoGo tasks; short-term visual working memory was investigated using Visual N-back Test. We found that performances of all tasks were similar for dyslexia and control groups in simple conditions but performance deteriorated for all three groups as soon as task was complex. Children having ADHD and dyslexia together had worse performance. Our results showed no deficits for children with dyslexia in visual working memory or visual selective and sustained attention even when reaction times are prolonged. But we found deficits for children having more than one neurodevelopmental condition (ADHD+dyslexia). There was not found any correlation between performances of different tasks. We conclude that deficits of visual attention and visual working memory might not be related to impairment of reading skills in dyslexic children. Even when children with more than one neurodevelopmental disorders show some deficits in visual attention and visual working memory, those deficits alone cannot be accounted for specific deficits of complex neurobehavioral disorders.

Does McCollough effect provide evidence for implicit change perception?

The possibility of implicit change detection in the visual scene is one of the central issues of a change detection process. The present work was aimed at studying the possibility of implicit perception of color changes. With this end, we have acquired the McCollough effect (MCE) with no possibility of explicit perception of the inducing stimulus color. The experiments were conducted on 40 male and female subjects with normal color vision. The MCE acquisition occurred using only one inducing stimulus - a vertical black-green grating. In the adaptation period the grating was presented as short expositions, with an instant substitution of the stimulus by so-called "deleting" image, whose presentation played simultaneously a role of an interstimulus interval. Owing to the fact that the time of exposition was selected so as to allow for the subjects perceive explicitly but the form of an inducing stimulus (in this case the grating's orientation) and not the color of chromatic stripes between the black ones, the subjects couldn't, in the adaptation period, perceive explicitly either the color per se or its appearance-disappearance. In spite of this, in a definite part of subjects (approximately in 20%) the effect was acquired indicating that in the adaptation period perception of not only color but also of its appearance-disappearance did occur, i.e. there took place implicit perception of color change. This result can be viewed as a confirmation of the visual system's ability of implicit change perception.

Effects of oxytocin on behaviour and memory in rats subjected to chronic restrained stress.

We studied whether 21 days of restraint chronic stress would affect the contextual fear conditioning, a memory task with hippocampal-dependent components and anxiety- like behavior in the open field, and to determine whether oxytocin treatment could prevent the chronic stress induced memory and emotional disturbances. Restraint-stressed rats were injected daily (21 days) with oxytocin (1 mg/kg) or saline then tested in open field (day 22) and contextual fear conditioning task (days 23-24). Our data demonstrate that chronic restraint stress induces some behavioural changes in both saline-treated and oxytocin-treated animals. Particularly, in the open field the animals both groups were characterized by hyper-locomotion. However, oxytocin-treated animals spent more time in the inner area of the open field, which indicates to decreased anxiety- related behaviour in oxytocin-treated animals versus the saline-treated ones. In additional restraint stress decreased freezing reaction to context, irrespective of whether oxytocin was given or not. Our findings indicate that during stress OT may be involved in the regulation of emotional behavior and memory via different ways. The elucidation of corresponding mechanisms is of great importance.