Department of Special Education

Dyslexia, a specific reading disability, is one of the most common psychological problems which seriously impairs school achievement and interferes with the acquisition of knowledge of written sources. As the hereditary component of dyslexia is becoming more and more firmly established nowadays, there has been a growing interest in investigations of children at familial risk for dyslexia before the onset of reading instruction, given that infants and kindergartners born to families with a background of developmental dyslexia have an increased risk of becoming dyslexic. The aim of the present article is to review current electrophysiological studies of infants and kindergartners with and without familial risk for dyslexia in relation to reading acquisition.

Event-Related Potentials (ERPs) are relative small changes in the electroencephalogram in time locked to a given event or stimulus. ERP components can provide evidence for the existence, order and timing of the independent process of information processing. ERPs are shown to be effective indices of auditory processes involved in speech perception and thus, apparently also helpful in revealing the neuronal basis of language problems associated with difficulties in reading. The auditory processing of physical stimulus features can be measured by the mismatch negativity (MMN). MMN is a negative component of auditory ERP, which is elicited by any discriminable change (deviant stimulus) in some repetitive aspect (standard stimulus) in the ongoing auditory stimulation, reflecting the brain's automatic change detection process. Some studies have also measured the N100, a negative component elicited about 100msec, thought to represent the initial extraction of information from the sensory analysis of the stimulus.

Several ERP studies have found differences between infants and kindergartners at familial risk for dyslexia and controls in MMN and N100, during the processing of consonant-vowel syllables. The results of these studies demonstrate that infants born with a familiar risk for dyslexia process speech/auditory stimulus durations differently from controls. MMN and N100 have shown to be potential indicators, each revealing somewhat different aspects of subtle weaknesses of auditory processing which may reduce the accuracy of phonological representations thought to form a central core deficit in dyslexia. Common to these studies is the tendency of right hemisphere dominance in the ERP responses of the at-risk group and left hemisphere dominance in the typically developing group. Results of more recent studies also suggest that early deficits in children at-risk for dyslexia are not restricted to lower level auditory or phonological processing, but also involve higher-order language skills such as lexical and semantic processing. ERPs have also been found to relate to later language outcomes. Longitudinal studies which found out that electrophysiological measures obtained at birth successfully discriminate between infants who will display later, during their school years, different levels of reading skills, raise strong possibilities regarding the early identification of children with potential language and/or reading problems.

Overall, the ERP findings we discuss here are promising because they indicate that the ERP technique can reveal new and useful information about underlying brain function that is related to rapid perceptual processing in infants and kindergartners. This review also suggests that ERPs during infancy may -in the not too distant future- be a useful tool for early screening, which might be employed even at an individual level. Identification of early precursors would not only be crucial for the understanding of the nature of dyslexic disorders but also enable both an earlier than present onset of intervention, and a focus of intervention efforts on those children in the risk group that are in need of support. This opens up the possibility that reading and language problems could be tackled before becoming serious during the school years.

Dyslexia is a multi-symptomatic and heterogeneous disorder incorporating a wide variety of cognitive difficulties, and which is neurobiological in origin. This article attempts to provide a brief overview of contemporary and often controversial theories and research findings on the causes of dyslexia. Our first aim was to give a picture of the extensive range of difficulties associated with what we call dyslexia, in order to understand its complexity and its possible causes. Our second and more important aim was to present an attempt for the convergence and synthesis of the causal theories on dyslexia based on the latest research findings. These findings indicate that a synthetic and complementary conception of the recent theoretical approaches to dyslexia could lead to a more satisfactory and more complete explanation of the symptoms and the causes of this disorder than the individual theories on their own.

The interest in the role of cerebellum in cognitive functioning has been increasing in recent days, based on both theoretical considerations and empirical evidence. The first aim of this study was to provide an introductory overview of the recently acknowledged role of the cerebellum in a number of cognitive processes, with special emphasis on its implication in speech and language functions. For this purpose we present neuropsychological, anatomical and neuroimaging studies conducted over the past two decades which have shown that in human the cerebellum is implicated in diverse higher cognitive functions, such as language, memory, visuospatial skills, executive functions, thought modulation, and emotional regulation of behaviour. The second aim was to examine further the hypothesis of cerebellar involvement in verbal fluency providing evidence from a preliminary neuropsychological study. For this purpose two standardized verbal fluency tasks (a phonological task and a semantic task) were administered to four patients who suffered from cerebellar dysfunction due to hemorrhage or tumour at the right cerebellum area. Our findings showed that the verbal fluency deficit seen in cerebellar patients is linked both to phonological and semantic processing. Overall, the results of this preliminary study support the view of cerebellar contribution to verbal fluency, extending its role to cognitive aspects of language functions.

The cerebellum is one of the most consistent sites of neuroanatomic abnormality in autism, but the motor consequences of the possible cerebellar dysfunction are poorly documented. The purpose of the present study was to examine individuals with autism, mental retardation and a normally intelligent comparison group of children in their performance on tasks sensitive to cerebellar function. Forty-two children, aged 7.7 to 12.8 years, were tested in nine cerebellar tests. Fourteen of them were persons with autism, fourteen were mentally retarded with IQs comparable to those of the autistic group and the other fourteen were typical children. The three groups were age- and sex-matched. The autistic group was hypotonic and there performance was significantly lower than that of typical children for most cerebellar tasks, notably those requiring fine motor skill and balance. They were worse than children with mental retardation in half of the tasks. In contrast, there was no significant difference between the three groups in tasks independent of cerebellar function. This pilot study supports the hypothesis of cerebellar dysfunction in autism and calls for further research.

Dyslexia is the most common and carefully studied of the learning disabilities in school-age children. It is characterized by a marked impairment in the development of reading skills, and affects a large number of people. The prevalence of dyslexia shows considerable cross-national variation. Additionally, a plethora of research studies have indicated that there are more boys than girls with reading difficulties. The aim of this study was to identify the frequency and gender ratio of dyslexia in a sample of Greek adolescents and their siblings. 598 secondary school students (Mean age 13.33, SD = 1.49) who attended mainstream public schools participated in this study. The prevalence of dyslexia in this study was estimated at 5.52%, a finding consistent with the data from other countries with “pure” orthographies. Statistical analysis revealed significant differences in the prevalence of dyslexia between gender (7.6% male, 3.8% female), which means that boys were twice as likely to be identified as dyslexic than their female peers. Additionally, statistically significant differences were observed between dyslexics who had a parent suffering from dyslexia (15.1%), compared to normal readers (1.8%), but no differences were observed between the two groups as for the frequency of brain injuries. Overall, our findings are in accordance with the results of previous national studies indicating the universal existence and the biological basis of this developmental disability.

Handedness is marked by the preference of one hand over another for fine motor tasks, especially writing. Usually, only one hand is considered dominant; however, there are individuals who exhibit the ability to use both hands equally (mixed-handers). The aim of this study was to identify the incidence for handedness in a sample of Greek adolescents and examine possible gender differences in handedness among these adolescents and their siblings. 634 secondary school students (Mean age 13.38, SD = 1.47) who attended mainstream public schools participated in this study. All students completed the Edinburgh Handedness Inventory (EHI). Students were divided in three groups, namely right-handers (an EHI +50 to +100), mixed-handers (an EHI -49 to +49) and left-handers (an EHI -100 to -50). This process resulted in the classification of 544 adolescents (85.8%) as right-handed, 46 adolescents (7.3%) as left-handed and 44 adolescents (6.9%) as non-lateralized (ambidextrous). Contrary to previous research, the statistical analysis conducted did not reveal any significant differences in the prevalence of handedness between genders. Nevertheless, our data suggest that men might be more prone to ambidexterity. Similarly, although some interesting trends were observed in our data, the statistical analyses performed did not confirm the familial effect upon handedness and the pathological left-handedness hypotheses. The paper concludes with underlining the significance of the evidence presented here and discusses the inconclusive findings often reported in the literature concerning the association of handedness with family history and brain injury.

The study of multiple abilities or intelligences could be a very promising field of research for students with learning difficulties, in order to build into alternative learning plans to enhance language acquisition and reading ability. The main purpose of the present study was to assess the relationship between dyslexia and multiple intelligences as described by Gardner (1983). A total of 117 secondary school students (39 dylexic and 78 typical readers) examined using the Multiple Intelligences Test. Results showed that dyslexic students displayed a preference for spatial intelligence and had less linguistic abilities, compared to the typical readers. Moreover, scores on the spatial intelligence scale were positively related to the likelihood of being member of the dyslexic group while, scores on the linguistic intelligence were negatively associated to this likelihood. The paper discusses these results in the light of recent research on abilities and disabilities associated with dyslexia, as well as in terms of their application to classroom learning for students with dyslexia.

Patients with chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea syndrome (OSAS) show similar
neurocognitive impairments. Effects aremore apparent in severe cases,whereas inmoderate andmild cases the effects are equivocal.
The exactmechanism that causes cognitive dysfunctions in both diseases is still unknown and only suggestions have beenmade for
each disease separately.Theprimary objective of this review is to present COPDand OSAS impact on cognitive functions. Secondly,
it aims to examine the potential mechanisms by which COPD and OSAS can be linked and provide evidence for a common
nature that affects cognitive functions in both diseases. Patients with COPD and OSAS compared to normal distribution show
significant deficits in the cognitive abilities of attention, psychomotor speed,memory and learning, visuospatial and constructional
abilities, executive skills, and language. The severity of these deficits in OSAS seems to correlate with the physiological events such
as sleep defragmentation, apnea/hypopnea index, and hypoxemia, whereas cognitive impairments in COPD are associated with
hypoventilation, hypoxemia, and hypercapnia.These factors aswell as vascocerebral diseases and changes in systemic hemodynamic
seem to act in an intermingling and synergistic way on the cause of cognitive dysfunctions in both diseases. However, low blood
oxygen pressure seems to be the dominant factor that contributes to the presence of cognitive deficits in both COPD and OSAS.