Marcus Hasselhorn

Grey Matter Alterations Co-Localize with Functional Abnormalities in Developmental Dyslexia: An ALE Meta- Analysis

The neural correlates of developmental dyslexia have been investigated intensively over the last two decades and reliable evidence for a dysfunction of left-hemispheric reading systems in dyslexic readers has been found in functional neuroimaging studies. In addition, structural imaging studies using voxel-based morphometry (VBM) demonstrated grey matter reductions in dyslexics in several brain regions. To objectively assess the consistency of these findings, we performed activation likelihood estimation (ALE) meta-analysis on nine published VBM studies reporting 62 foci of grey matter reduction in dyslexic readers. We found six significant clusters of convergence in bilateral temporo-parietal and left occipito-temporal cortical regions and in the cerebellum bilaterally. To identify possible overlaps between structural and functional deviations in dyslexic readers, we conducted additional ALE meta-analyses of imaging studies reporting functional underactivations (125 foci from 24 studies) or overactivations (95 foci from 11 studies ) in dyslexics. Subsequent conjunction analyses revealed overlaps between the results of the VBM meta-analysis and the meta-analysis of functional underactivations in the fusiform and supramarginal gyri of the left hemisphere. An overlap between VBM results and the meta-analysis of functional overactivations was found in the left cerebellum. The results of our study provide evidence for consistent grey matter variations bilaterally in the dyslexic brain and substantial overlap of these structural variations with functional abnormalities in left hemispheric regions.

The association between gray matter volume and reading proficiency: A longitudinal study of beginning readers

Neural systems involved in the processing of written language have been identified by a number of functional imaging studies. Structural changes in cortical anatomy that occur in the course of literacy acquisition, however, remain largely unknown. Here, we follow elementary school children over their first 2 years of formal reading instruction and use tensor-based morphometry to relate reading proficiency to cortical volume at baseline and follow-up measurement as well as to intraindividual longitudinal volume development between the two measurement time points. A positive relationship was found between baseline gray matter volume in the left superior temporal gyrus and subsequent changes in reading proficiency. Furthermore, a negative relationship was found between reading proficiency at the second measurement time point and intraindividual cortical volume development in the inferior parietal lobule and the precentral and postcentral gyri of the left hemisphere. These results are interpreted as evidence that reading acquisition is associated with preexisting structural differences as well as with experience-dependent structural changes involving dendritic and synaptic pruning.

Working Memory in Children With Learning Disabilities in Reading Versus Spelling Searching for Overlapping and Specific Cognitive Factors

In transparent orthographies like German, isolated learning disabilities in either reading or spelling are common and occur as often as a combined reading and spelling disability. However, most issues surrounding the cognitive causes of these isolated or combined literacy difficulties are yet unresolved. Recently, working memory dysfunctions have been demonstrated to be promising in explaining the emergence of literacy difficulties. Thus, we applied a 2 (reading disability: yes vs. no) × 2 (spelling disability: yes vs. no) factorial design to examine distinct and overlapping working memory profiles associated with learning disabilities in reading versus spelling. Working memory was assessed in 204 third graders, and multivariate analyses of variance were conducted for each working memory component. Children with spelling disability suffered from more pronounced phonological loop impairments than those with reading disability. In contrast, domain-general central-executive dysfunctions were solely associated with reading disability, but not with spelling disability. Concerning the visuospatial sketchpad, no impairments were found. In sum, children with reading disability and those with spelling disability seem to be characterized by different working memory profiles. Thus, it is important to take both reading and spelling into account when investigating cognitive factors of literacy difficulties in transparent orthographies.

Developmental changes in the association between approximate number representations and addition skills in elementary school children

The approximate number system (ANS) is assumingly related to mathematical learning but evidence supporting this assumption is mixed. The inconsistent findings might be attributed to the fact that different measures have been used to assess the ANS and mathematical skills. Moreover, associations between the performance on a measure of the ANS and mathematical skills may be discontinuous, i.e., stronger for children with lower math scores than for children with higher math scores, and may change with age. The aim of the present study was to examine the development of the ANS and arithmetic skills in elementary school children and to investigate how the relationship between the ANS and arithmetic skills develops. Individual markers of childrens ANS (internal Weber fractions and mean reaction times in a non-symbolic numerical comparison task) and addition skills were assessed in their first year of school and 1 year later. Children showed improvements in addition performance and in the internal Weber fractions, whereas mean reaction times in the non-symbolic numerical comparison task did not change significantly. While childrens addition performance was associated with the internal Weber fractions in the first year, it was associated with mean reaction times in the non-symbolic numerical comparison task in the second year. These associations were not found to be discontinuous and could not be explained by individual differences in reasoning, processing speed, or inhibitory control. The present study extends previous findings by demonstrating that addition performance is associated with different markers of the ANS in the course of development.

Text-fading based training leads to transfer effects on children's sentence reading fluency.

Previous studies used a text-fading procedure as a training tool with the goal to increase silent reading fluency (i.e., proficient reading rate and comprehension). In recently published studies, this procedure resulted in lasting reading enhancements for adult and adolescent research samples. However, studies working with children reported mixed results. While reading rate improvements were observable for Dutch reading children in a text-fading training study, reading fluency improvements in standardized reading tests post-training attributable to the fading manipulation were not detectable. These results raise the question of whether text-fading training is not effective for children or whether research design issues have concealed possible transfer effects. Hence, the present study sought to investigate possible transfer effects resulting from a text-fading based reading training program, using a modified research design. Over a period of 3 weeks, two groups of German third-graders read sentences either with an adaptive text-fading procedure or at their self-paced reading rate. A standardized test measuring reading fluency at the word, sentence, and text level was conducted pre- and post-training. Text level reading fluency improved for both groups equally. Post-training gains at the word level were found for the text-fading group, however, no significant interaction between groups was revealed for word reading fluency. Sentence level reading fluency gains were found for the text-fading group, which significantly differed from the group of children reading at their self-paced reading routine. These findings provide evidence for the efficacy of text-fading as a training method for sentence reading fluency improvement also for children.

Spatial representations of numbers and letters in children

Different lines of evidence suggest that childrens mental representations of numbers are spatially organized in form of a mental number line. It is, however, still unclear whether a spatial organization is specific for the numerical domain or also applies to other ordinal sequences in children. In the present study, children (n = 129) aged 8–9 years were asked to indicate the midpoint of lines flanked by task-irrelevant digits or letters. We found that the localization of the midpoint was systematically biased toward the larger digit. A similar, but less pronounced, effect was detected for letters with spatial biases toward the letter succeeding in the alphabet. Instead of assuming domain-specific forms of spatial representations, we suggest that ordinal information expressing relations between different items of a sequence might be spatially coded in children, whereby numbers seem to convey this kind of information in the most salient way.

Neurocognitive precursors of difficulties in reading and arithmetic

Difficulties in reading and arithmetic especially among primary school children are highly prevalent and pervasive cognitive impairments that severely challenge affected individuals in achieving functional cognitive and social competence. About 25% (OECD, 2006) to 36% (Perie, Grigg, & Donahue, 2005) of school children exhibit difficulties in the acquisition of reading, spelling and arithmetic. Such learning disabilities have been found to be related to neurocognitive deficits as well as social and/or cultural background. In order to understand, diagnose, remediate and prevent learning disabilities in reading and arithmetic, it is important to clarify the underlying factors and neurocognitive mechanisms that are substantially involved in the development of these skills. During the last couple of years, early phonological or quantity processing, automatization efficiency, attentional mechanisms, brain modalities synchronization and working memory functioning have been identified to predict the quality of the acquisition of reading and arithmetic during elementary school years. In particular, specific neurocognitive processes related to working memory and automatization (as measured by the rapid naming of items) seem to be crucially involved in the acquisition of both reading and arithmetic skills. Although some authors suggested that reading and arithmetic difficulties are skill-specific in nature (e.g., Dehaene, Spelke, Pinel, Stanescu, & Tsivkin, 1999; Lundberg, 2009), recent findings indicate that different learning difficulties share some common characteristics (e.g., Dehaene & Cohen, 2007). Accordingly, the current volume of the Journal of Neurolinguistics addresses issues surrounding the debate of domain specificity versus domain generality of the underlying factors of difficulties in reading and arithmetic by considering behavioral as well as brain-imaging approaches. Although recently research activities addressing the underlying factors of domain-specific learning difficulties have increased continuously, the specification of precursors of reading and arithmetic skills is still at its beginning. The contributions of the present special issue entitled Neurocognitive Precursors of Difficulties in Reading and Arithmetic mirror this most recent research focus. The first paper by Amir Shiran and Zvia Breznitz addresses the enhancement of working memory functioning among dyslexic and skilled readers by applying a training program over a six-week period. ERP measures were used to examine the benefits of the training. Results show that dyslexic and skilled readers’ working memory functioning and reading skills can be improved by training. Thus, the findings corroborate the view of the plasticity potential of the neural system and also emphasize the role of working memory in the enhancement of reading related skills. The second paper by Sabine Heim, Jennifer Thomas Friedman, Andreas Keil, and April A. Benasich reveals an altered temporal organization of sensory oscillatory activity in children with languagelearning impairment (LLI) when processing rapid sequences in a deviant detection task during EEG recording. The findings suggest that individuals with LLI are impaired in their ability to integrate rapidly presented, brief acoustic events in sensory cortex. Since children with LLI mostly suffer from

The Training of Morphological Decomposition in Word Processing and Its Effects on Literacy Skills

This study set out to examine the effects of a morpheme-based training on reading and spelling in fifth and sixth graders (N = 47), who present poor literacy skills and speak German as a second language. A computerized training, consisting of a visual lexical decision task (comprising 2,880 items, presented in 12 sessions), was designed to encourage fast morphological analysis in word processing. The children were divided between two groups: the one underwent a morpheme-based training, in which word-stems of inflections and derivations were presented for a limited duration, while their pre- and suffixes remained on screen until response. Another group received a control training consisting of the same task, except that the duration of presentation of a non-morphological unit was restricted. In a Word Disruption Task, participants read words under three conditions: morphological separation (with symbols separating between the words’ morphemes), non-morphological separation (with symbols separating between non-morphological units of words), and no-separation (with symbols presented at the beginning and end of each word). The group receiving the morpheme-based program improved more than the control group in terms of word reading fluency in the morphological condition. The former group also presented similar word reading fluency after training in the morphological condition and in the no-separation condition, thereby suggesting that the morpheme-based training contributed to the integration of morphological decomposition into the process of word recognition. At the same time, both groups similarly improved in other measures of word reading fluency. With regard to spelling, the morpheme-based training group showed a larger improvement than the control group in spelling of trained items, and a unique improvement in spelling of untrained items (untrained word-stems integrated into trained pre- and suffixes). The results further suggest some contribution of the morpheme-based training to performance in a standardized spelling task. The morpheme-based training did not, however, show any unique effect on comprehension. These results suggest that the morpheme-based training is effective in enhancing some basic literacy skill in the population examined, i.e., morphological analysis in word processing and the access to orthographic representations in spelling, with no specific effects on reading fluency and comprehension.

Differences in arithmetic performance between Chinese and German adults are accompanied by differences in processing of non-symbolic numerical magnitude

Human beings are assumed to possess an approximate number system (ANS) dedicated to extracting and representing approximate numerical magnitude information. The ANS is assumed to be fundamental to arithmetic learning and has been shown to be associated with arithmetic performance. It is, however, still a matter of debate whether better arithmetic skills are reflected in the ANS. To address this issue, Chinese and German adults were compared regarding their performance in simple arithmetic tasks and in a non-symbolic numerical magnitude comparison task. Chinese participants showed a better performance in solving simple arithmetic tasks and faster reaction times in the non-symbolic numerical magnitude comparison task without making more errors than their German peers. These differences in performance could not be ascribed to differences in general cognitive abilities. Better arithmetic skills were thus found to be accompanied by a higher speed of retrieving non-symbolic numerical magnitude knowledge but not by a higher precision of non-symbolic numerical magnitude representations. The group difference in the speed of retrieving non-symbolic numerical magnitude knowledge was fully mediated by the performance in arithmetic tasks, suggesting that arithmetic skills shape non-symbolic numerical magnitude processing skills.

A Fact Retrieval Account of the Acceleration Phenomenon

Breznitz (J Educ Psychol 89:289–297, 1987a; Fluency in reading: synchronization of processes. Erlbaum, Mahwah, 2006) demonstrated that a fading manipulation, which continuously erases text based on the individual reading rate, results in improved reading performance. Several studies using this fading procedure showed that children as well as adults with different reading proficiency levels and in different languages were able to increase their reading rate and reading comprehension in a fading condition, characterizing the Acceleration Phenomenon. Considering the close interconnection of reading fluency and reading comprehension, a fact retrieval account for achievement enhancements induced by the fading manipulation is presented in this chapter. It is hypothesized, that if information can be processed at a high level of automaticity and available lexical entries can be accessed rapidly, reading performance can be improved by means of imposing a time limitation. Hence, the nature of the fading manipulation may induce a shift to faster and more elaborated strategies, such as direct fact retrieval, resulting in improved performance. Different empirical outcomes from the reading and the arithmetic domain are demonstrated and the generalizability of the Acceleration Phenomenon across academic domains is discussed.