Sleep-Related Declarative Memory Consolidation in Children and Adolescents with Developmental Dyslexia.

Sleep has a crucial role in memory processes, and maturational changes in sleep electrophysiology are involved in cognitive development. Albeit both sleep and memory alterations have been observed in Developmental Dyslexia (DD), their relation in this population has been scarcely investigated, particularly concerning topographical aspects. The study aimed to compare sleep topography and associated sleep-related declarative memory consolidation in participants with DD and normal readers (NR). Eleven participants with DD and 18 NR (9-14 years old) underwent a whole-night polysomnography. They were administered a word pair task before and after sleep to assess for declarative memory consolidation. Memory performance and sleep features (macro and microstructural) were compared between the groups, and the intercorrelations between consolidation rate and sleep measures were assessed. DD showed a deeper worsening in memory after sleep compared to NR and reduced slow spindles in occipito-parietal and left fronto-central areas. Our results suggest specific alterations in local sleep EEG (i.e., sleep spindles) and in sleep-dependent memory consolidation processes in DD. We highlight the importance of a topographical approach, which might shed light on potential alteration in regional cortical oscillation dynamics in DD. The latter might represent a target for therapeutic interventions aimed at enhancing cognitive functioning in DD.

Later School Start Time: The Impact of Sleep on Academic Performance and Health in the Adolescent Population.

The crucial role of sleep in physical and mental health is well known, especially during the developmental period. In recent years, there has been a growing interest in examining the relationship between sleep patterns and school performance in adolescents. At this stage of life, several environmental and biological factors may affect both circadian and homeostatic regulation of sleep. A large part of this population does not experience adequate sleep, leading to chronic sleep restriction and/or disrupted sleep-wake cycles. Studies investigating the effects of different sleep-wake schedules on academic achievement showed that impaired sleep quality and quantity are associated with decreased learning ability and compromised daytime functioning. This review focuses on the most recent studies that evaluated the effects of modified school start time on sleep patterns and related outcomes. Moreover, based on the available empirical evidence, we intend to propose a direction for future studies targeted to implement prevention or treatment programs by modifying sleep timing.

Quantitative assessment of drawing tests in children with dyslexia and dysgraphia.

Drawing tests in children diagnosed with dyslexia and dysgraphia were quantitatively compared. Fourteen children with dysgraphia, 19 with dyslexia and 13 normally developing were asked to copy 3 figures: a circle, a square and a cross. An optoelectronic system allowed the acquisition of the drawing track in three-dimensions. The participants' head position and upper limb movements were measured as well. A set of parameters including movement duration, velocity, length of the trace, Range of Motion of the upper limb, was computed and compared among the 3 groups. Children with dyslexia traced the circle faster than the other groups. In the cross test, dyslexic participants showed a reduced execution time and increased velocity while drawing the horizontal line. Children with dyslexia were also faster in drawing certain sides of square with respect to the other groups.

Age-Related Cortical Thickness Reduction in Non-Demented Down's Syndrome Subjects.

BACKGROUND AND PURPOSE: The aim of this study was to investigate the characteristic pattern of age-related cortical thinning in patients with Down Syndrome (DS), as assessed by MRI and automatic cortical thickness measurements. METHODS: Ninety-one non-demented subjects with DS (range 11-53 years) were examined using a 1.5 T scanner. MRI-based quantification of cortical thickness was performed using FreeSurfer software package., The Pearson product-moment correlation coefficient between age and mean cortical thickness was evaluated for all subjects participating in the study. RESULTS: A significant negative correlation between cortical thickness and age was found bilaterally in the frontal, temporal, parietal and cingulate gyrus. Specific investigation of cerebral lobes showed a more evident involvement of the frontal one, compared to others. Moreover, the age related reduction of cortical thickness appeared to be more significant and rapid in patients between 20 and 30 years of age. CONCLUSIONS: Our findings showed that Down Syndrome subjects are affected by a diffuse cortical thinning. The involvement of cortical structures can be observed at an earlier age than previous studies have reported.

Silent reading fluency: Implications for the assessment of adults with developmental dyslexia.

INTRODUCTION: Understanding silent reading fluency (SRF) is of a paramount importance, given that silent reading is the principal manner of reading for capable readers. But the assessment of SRF is not commonly useful for identifying students with reading difficulties and monitoring their progress. The paper presents the SRF scores of adults with dyslexia compared to SRF scores of skilled readers and discusses the power of the SRF measure in identifying adults with specific learning disorders with impairment in reading. METHOD: Participants recruited were 68 dyslexic and age-matched skilled adult readers (18-48 years old). Among them, 24 were skilled readers with a university degree (GRS), 22 were skilled readers with a high school diploma (DSR), and 22 participants had been diagnosed with dyslexia (DR). We used a standardized oral reading fluency (ORF) test and an original SRF task to measure the reading fluency. RESULTS: All participants increased their reading fluency in silent mode (p < .001). Nonetheless, the average speed of the oral reading was 7.19 syllables per second (syl/s) for the GSR group, 7.11 syl/s for the DSR group, and 4.95 syl/s for the DR group. The average speed of the silent reading was 11.62 syl/s and 10.75 syl/s for GSR and DSR, respectively, and 6.15 syl/s for DR. The reading fluency differential (Δf) between ORF and SRF was significantly different among the dyslexic participants and the other two groups. CONCLUSIONS: Our results strongly suggest that dyslexic readers are less capable of significantly improve their reading speed when they read silently. Thus SRF could be considered a suitable parameter for identifying older students and adults with impairment in reading. A broader investigation of the issues surrounding silent reading is needed.

Age effects on cortical thickness in young Down's syndrome subjects: a cross-sectional gender study.

INTRODUCTION: The aim of this study was to determine differences in the characteristic pattern of age-related cortical thinning in men and women with Down's syndrome (DS) by means of MRI and automatic cortical thickness measurements and a cross-sectional design, in a large cohort of young subjects. METHODS: Eighty-four subjects with DS, 30 females (11-35 years, mean age ± SD = 22.8 ± 5.9) and 54 males (11-35 years, mean age ± SD = 21.5 ± 6.5), were examined using a 1.5-T scanner. MRI-based quantification of cortical thickness was performed using FreeSurfer software package. For all subjects participating in the study, the Pearson product-moment correlation coefficient between age and mean cortical thickness values has been evaluated. RESULTS: A significant negative correlation between cortical thickness and age was found in female DS subjects, predominantly in frontal and parietal lobes, bilaterally. In male DS subjects, a significant negative correlation between cortical thickness and age was found in the right fronto-temporal lobes and cingulate regions. Whole brain mean cortical thickness values were significantly negative correlated with age only in female DS subjects. CONCLUSIONS: Females with Down's syndrome showed a strong correlation between cortical thickness and age, already in early age. We suggest that the cognitive impairment due to hormonal deficit in the postmenopausal period could be emphasized by the early structural decline of gray matter in female DS subjects.

Assessing decoding ability: the role of speed and accuracy and a new composite indicator to measure decoding skill in elementary grades.

Tools for assessing decoding skill in students attending elementary grades are of fundamental importance for guaranteeing an early identification of reading disabled students and reducing both the primary negative effects (on learning) and the secondary negative effects (on the development of the personality) of this disability. This article presents results obtained by administering existing standardized tests of reading and a new screening procedure to about 1,500 students in the elementary grades in Italy. It is found that variables measuring speed and accuracy in all administered reading tests are not Gaussian, and therefore the threshold values used for classifying a student as a normal decoder or as an impaired decoder must be estimated on the basis of the empirical distribution of these variables rather than by using the percentiles of the normal distribution. It is also found that the decoding speed and the decoding accuracy can be measured in either a 1-minute procedure or in much longer standardized tests. The screening procedure and the tests administered are found to be equivalent insofar as they carry the same information. Finally, it is found that speed and accuracy act as complementary effects in the measurement of decoding ability. On the basis of this last finding, the study introduces a new composite indicator aimed at determining the student's performance, which combines speed and accuracy in the measurement of decoding ability.

Response inhibition and adaptations to response conflict in 6- to 8-year-old children: evidence from the Simon effect.

Several studies have shown that the Simon effect, which is the advantage of spatial correspondence between stimulus and response locations when the stimulus location is task-irrelevant, decreases with increasing response times and is affected by preceding-trial correspondence. These modulations suggest the existence of control mechanisms that adapt our behavior to current goals by responding to the conflict experienced within a trial and by preventing the recurrence of a conflict in the subsequent trial. The aim of the present study was to assess whether these control mechanisms, which are well consolidated in adults and in children older than 8 years of age, are present in children between 6 and 8 years old. To this end, we tested 32 first-grade (6-7 years) and 34 second-grade (7-8 years) children on a Simon task in which correspondence sequence was manipulated on a trial-by-trial basis. The Simon effect was larger for first- than for second-graders and decreased with increasing response times only in second-graders. Crucially, for both groups, the effect was reduced when the preceding trial was noncorresponding, and the reductions were comparable for the two groups, indicating that trial-by-trial control mechanisms are already present in first-grade children and may be dissociated from within-trial control adjustments.

A new procedure to measure children's reading speed and accuracy in Italian.

Impaired readers in primary school should be early recognized, in order to asses a targeted intervention within the school and to start a teaching that respects the difficulties in learning to read, to write and to perform calculations. Screening procedures, inside the primary schools aimed at detecting children with difficulties in reading, are of fundamental importance for guaranteeing an early identification of dyslexic children and reducing both the primary negative effects--on learning--and the secondary negative effects--on the development of the personality--of this disturbance. In this study, we propose a new screening procedure measuring reading speed and accuracy. This procedure is very fast (it is exactly 1 min long), simple, cheap and can be provided by teachers without technical knowledge. On the contrary, most of the currently used diagnostic tests are about 10 min long and must be provided by experts. These two major flaws prevent the widespread use of these tests. On the basis of the results obtained in a survey on about 1500 students attending primary school in Italy, we investigate the relationships between variables used in the screening procedure and variables measuring speed and accuracy in the currently used diagnostic tests in Italy. Then, we analyse the validity of the screening procedure from a statistical point of view, and with an explorative factor analysis, we show that reading speed and accuracy seem to be two separate symptoms of the dyslexia phenomenon.

Cortical sources of resting state EEG rhythms are abnormal in dyslexic children.

OBJECTIVE: Previous studies have been inconclusive whether dominant resting state alpha rhythms differ in amplitude in dyslexic subjects when compared to control subjects, being these rhythms considered as a reflection of effective cortical neural synchronization and cognition. Here we used a validated EEG source estimation to test the hypothesis that resting state alpha rhythms are abnormal in dyslexic subjects and are related to reading deficits. METHODS: Eyes-closed resting state electroencephalographic (EEG) data were recorded in 26 dyslexics (12 males, mean age of 11 years ± 0.5 standard error of mean, SEM) and 11 age-matched normal control subjects (8 males, mean age of 11 years ± 0.7 SEM). EEG rhythms of interest, based on individual alpha frequency peak, were the following: about 2-4 Hz (delta), 4-6 Hz (theta), 6-8 Hz (alpha 1), 8-10 Hz (alpha 2), and 10-12 Hz (alpha 3). For the higher frequencies, we selected beta 1 (13-20 Hz), beta 2 (20-30 Hz), and gamma (30-40 Hz). Cortical EEG sources were estimated by low resolution electromagnetic tomography (LORETA). LORETA solutions were normalized across all voxels and frequencies. RESULTS: Compared to the control children, the dyslexics showed lower amplitude of parietal, occipital, and temporal alpha 2 and alpha 3 sources. In the dyslexics, some of these sources were correlated to reading time of pseudo-words (parietal alpha 2, r=-0.56, p=0.02; parietal alpha 3, r=-0.58, p=0.02; temporal alpha 3, r=-0.57, p=0.02); the higher the alpha power, the shorter the reading time. CONCLUSIONS: Dyslexic children are characterized by limited abnormalities of resting state EEG rhythms as to topography (posterior regions) and frequency (alpha), which were related to phonological encoding (pseudo-words reading). SIGNIFICANCE: Dyslexia may be associated to some functional impairment of cortical neuronal synchronization mechanisms involved in the resting state condition.

A new approach for the quantitative evaluation of drawings in children with learning disabilities.

A new method for a quantitative and objective description of drawing and for the quantification of drawing ability in children with learning disabilities (LD) is hereby presented. Twenty-four normally developing children (N) (age 10.6 ± 0.5) and 18 children with learning disabilities (LD) (age 10.3 ± 2.4) took part to the study. The drawing tasks were chosen among those already used in clinical daily experience (Denver Developmental Screening Test). Some parameters were defined in order to quantitatively describe the features of the children's drawings, introducing new objective measurements beside the subjective standard clinical evaluation. The experimental set-up revealed to be valid for clinical application with LD children. The parameters highlighted the presence of differences in the drawing features of N and LD children. This paper suggests the applicability of this protocol to other fields of motor and cognitive valuation, as well as the possibility to study the upper limbs position and muscle activation during drawing.

Real-word repetition as a predictor of grammatical competence in Italian children with typical language development.

BACKGROUND: Non-word repetition in children is a skill related to, but separable from grammatical ability. Lexical skill may bridge the gap between these two abilities. AIMS: The main aim was to determine whether real-word-repetition tasks could be better as predictors of grammatical ability than non-word-repetition tasks in children with typical language. This proposal was pursued because lexical knowledge was assumed to make performance in repetition tasks more representative of other language abilities, whereas non-word-repetition tasks are heavily influenced by phonological short-term memory. METHODS & PROCEDURES: In order to investigate this possibility, three repetition tasks (two real-word lists characterized by different lexical knowledge and one non-word list), were compared in three groups of three- to four-year-olds with typical language (42 children). Grammatical ability was tested through probes for third-person plural inflection and direct-object critic use. OUTCOMES & RESULTS: Real words were repeated more accurately than non-words and the non-words were more sensitive to Syllable length than real words. Performance on all repetition tasks was correlated with grammatical ability, but real words predicted variance in grammatical ability to a greater extent than non-words. CONCLUSIONS & IMPLICATIONS: Given the lexical information contained in real words, repetition of such words was a better predictor of grammatical ability than non-word repetition. Future research should replicate and extend these results. Tasks using real words may also have considerable clinical potential; for this reason, these tasks might also be included in studies of children with language impairment.

Neuropsychological deficits and neural dysfunction in familial dyslexia.

We report the neuropsychological profile and the pattern of brain activity during reading tasks in a sample of familial dyslexics. We studied our subjects with an in-depth neuropsychological assessment and with functional neuroimaging (fMRI) during word and pseudoword reading and false font string observations (baseline condition). The neuropsychological assessment revealed that familial dyslexia, in both persistent and compensated forms, is often associated with deficits in verbal short-term memory, phonological awareness and automatization abilities. The functional results showed a lack of activation in the posterior areas of the reading network. This study, together with the previously published VBM study (Brambati, S.M., Termine, C., Ruffino, M., Stella, G., Fazio, F., Cappa, S.F. and Perani, D., Regional reductions of gray matter volume in familial dyslexia, Neurology, 63 (2004) 742-5), provides a multiple modality evaluation of familial dyslexia. The neuropsychological assessment showed cognitive deficits associated with dyslexia that persist also in subjects with compensated reading deficit. Both the anatomical and the functional study point out a deficit in the posterior areas of the reading network.

How early does morpholexical reading develop in readers of a shallow orthography?

In this research, lexical and morpholexical reading in Italian children ages 8 to 10 years were investigated. Children and control adults were administered two tasks on words and pseudowords: visual lexical decision and naming. Word frequency effects in both lexical decision and naming were found in both children and adults. For all age groups pseudowords made up of roots and derivational suffixes were decided more frequently as possible words and were named more quickly and accurately than matched pseudowords with no morphological constituency. These results show that morpholexical reading is available and efficient in young readers of a shallow orthography, with similar patterns in children and adults.