Claudia Steinbrink

The contribution of white and gray matter differences to developmental dyslexia : Insights from DTI and VBM at 3.0 T

Developmental dyslexia is one of the most common neuropsychological disorders in children and adults. Only few data are available on the pathomechanisms of this specific dysfunction, assuming--among others--that dyslexia might be a disconnection syndrome of anterior and posterior brain regions involved in phonological and orthographic aspects of the reading process, as well as in the integration of phonemes and graphemes. Therefore, diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) were used to verify the hypothesis of altered white and gray matter structure in German dyslexic adults. DTI revealed decreased fractional anisotropy (FA) in bilateral fronto-temporal and left temporo-parietal white matter regions (inferior and superior longitudinal fasciculus). Significant correlations between white matter anisotropy and speed of pseudoword reading were found. In dyslexics, gray matter volumes (as measured by VBM) were reduced in the superior temporal gyrus of both hemispheres. So far, our results, based on a combined analysis of white and gray matter abnormalities, provide exceedingly strong evidence for a disconnection syndrome or dysfunction of cortical areas relevant for reading and spelling. Thus, we suggest that this imbalance of neuronal communication between the respective brain areas might be the crucial point for the development of dyslexia.

Functional significance of age-related differences in motor activation patterns

Recent functional MRI (fMRI) studies have revealed an increased task-related activation in older subjects during a variety of cognitive or perceptual tasks, which may signal beneficial compensatory activity to counteract structural and neurochemical changes associated with aging. Under the assumption that incremental movement rates are associated with an increased functional demand on the motor system, we used fMRI and acoustically paced movements of the right index finger at six different frequencies (2.0, 2.5, 3.0, 4.0, 5.0 and 6.0 Hz) to investigate the behavioral significance of additionally recruited brain regions in a group of healthy, older subjects (mean age 66 +/- 8 years) compared with a group of young (mean age 23 +/- 7 years) subjects. The actual tapping frequency (F(1,14) = 0.049, P = 0.829), the tapping interval (F(1,14) = 0.043, P = 0.847), and the error rates (F(1,14) = 0.058, P = 0.743) did not differ significantly between both groups, whereas there was a significant increase in reaction time in the older subjects (F(1,14) = 281.786, P < or = 0.001). At all frequencies, the older subjects demonstrated significant overactivation within the ipsilateral sensorimotor and premotor cortex. However, we did not observe an increased age-related overactivation during higher movements rates in these or other motor regions. Moreover, the magnitude of the hemodynamic response in overactivated regions remained constant across all frequencies. In contrast to cognitive tasks, these findings indicate that an age-related overactivation within the motor system is not related to the functional demand and does not necessarily reflect reorganization to compensate for the neurobiological changes of aging.

Contribution of the anterior insula to temporal auditory processing deficits in developmental dyslexia

Developmental dyslexia has been assumed to arise from general auditory deficits, compromising rapid temporal integration both of linguistic and nonlinguistic acoustic stimuli. Because the effort of auditory temporal processing of speech and nonspeech test materials may depend on presentation rate, fMRI measurements were performed in dyslexics and controls during passive listening to series of syllable and click sounds, using a parametric approach. Controls showed a decrease of hemodynamic brain activation within the right and an increase within the left anterior insula as a function of the presentation rate both of click as well as syllable trains. By contrast, dyslexics exhibited this profile of hemodynamic responses under the nonspeech condition only. As concerns syllables, activation in dyslexics did not depend on presentation rate. Moreover, a subtraction analysis of hemodynamic main effects across conditions and groups revealed decreased activation both of the left and right anterior insula in dyslexics compared to controls during application both of click and syllables. These results indicate, in line with preceding studies, that the insula of both hemispheres is involved in auditory temporal processing of nonlinguistic auditory stimuli and demonstrate, furthermore, that these operations of intrasylvian cortex also extend to the linguistic domain. In addition, our data suggest that the anterior insula represents an important neural correlate of deficient temporal processing of speech and nonspeech sounds in dyslexia. Hum Brain Mapp 2009.

Development of vocabulary and grammar in young German-speaking children assessed with a German language development inventory

Using a parent report instrument, the development of vocabulary and grammar was examined in 333 German-speaking children aged between 1;6 and 2;6. Grammar scales measured sentence complexity and inflectional morphology. Results indicate that vocabulary increased faster than sentence complexity and inflectional morphology. Within inflectional paradigms, noun plural and gender marking were acquired faster than case marking and verb inflections. Modals and copula were acquired most slowly. There was extensive variability on all language scales. The different language skills were strongly related, with grammatical development increasing non-linearly in dependence on vocabulary. There was a mild effect of gender favouring girls. The results converge with results of studies in other languages using a parent report instrument. There is some evidence for concurrent validity for the present questionnaire.

Neural Correlates of Working Memory Performance in Adolescents and Young Adults with Dyslexia.

Behavioral studies indicate deficits in phonological working memory (WM) and executive functioning in dyslexics. However, little is known about the underlying functional neuroanatomy. In the present study, neural correlates of WM in adolescents and young adults with dyslexia were investigated using event-related functional magnetic resonance imaging (fMRI) and a parametric verbal WM task which required the manipulation of verbal material. Dyslexics were not significantly slower than controls; however, they were less accurate with the highest WM demand. The functional analysis excluded incorrectly performed and omitted trials, thus controlling for potential activation confounds. Compared with control subjects, both increased and decreased activation of the prefrontal cortex were found in the dyslexic group. Dyslexics showed significantly more activation than controls with increasing WM demand in the left superior frontal gyrus (BA 8), as well as in the inferior frontal gyrus including Brocas area (BA 44) and its right homologue. Less activation was found in the middle frontal gyrus (BA 6) and in the superior parietal cortex (BA 7). A positive correlation between activation of prefrontal regions and verbal WM performance (as measured by digit span backwards) was found only in the dyslexic group. Accuracy deficits at the highest cognitive demand during the verbal WM task and the digit span backwards suggest that manipulation rather than maintenance is selectively impaired in dyslexics. The fMRI data provide further evidence for functional differences in cortical regions associated with language processing and executive function in subjects with dyslexia.

Neural correlates of temporal auditory processing in developmental dyslexia during German vowel length discrimination: an fMRI study.

This fMRI study investigated phonological vs. auditory temporal processing in developmental dyslexia by means of a German vowel length discrimination paradigm (Groth, Lachmann, Riecker, Muthmann, & Steinbrink, 2011). Behavioral and fMRI data were collected from dyslexics and controls while performing same-different judgments of vowel duration in two experimental conditions. In the temporal, but not in the phonological condition, hemodynamic brain activation was observed bilaterally within the anterior insular cortices in both groups and within the left inferior frontal gyrus (IFG) in controls, indicating that the left IFG and the anterior insular cortices are part of a neural network involved in temporal auditory processing. Group subtraction analyses did not demonstrate significant effects. However, in a subgroup analysis, participants performing low in the temporal condition (all dyslexic) showed decreased activation of the insular cortices and the left IFG, suggesting that this processing network might form the neural basis of temporal auditory processing deficits in dyslexia.

Different letter-processing strategies in diagnostic subgroups of developmental dyslexia also occur in a transparent orthography: Reply to a commentary by Spinelli et al.

The article was motivated by a commentary of Spinelli et al. (2010), who commented on our experimental study with dyslexic children (Lachmann & van Leeuwen, 2008). They questioned the unusually large reversed lexicality effect we reported for three of our dyslexic children for which word reading times were considerably longer than nonword reading times. We argued that, in principle, in a transparent orthography, such as German, children exist who have significant problems in word reading, but for whom nonword reading is normal. The extreme reversed lexically effect, however, may not be representative for the dyslexic population. Since we do not want to give the impression that our results were based on these three participants, we reran analyses on reaction times presented in Lachmann and van Leeuwen, this time excluding the data from the three individuals. Results were replicated. The constructive criticism has helped put both the diagnostics and our experimental results on even firmer ground. Both yield a consistent interpretation, in which two subgroups of dyslexics can be distinguished: one with generic activation problems; the other with a specific problem in phoneme-grapheme conversion.

Evidence for a General Auditory Processing Deficit in Developmental Dyslexia From a Discrimination Paradigm Using Speech Versus Nonspeech Sounds Matched in Complexity

PURPOSE It is unknown whether phonological deficits are the primary cause of developmental dyslexia or whether they represent a secondary symptom resulting from impairments in processing basic acoustic parameters of speech. This might be due, in part, to methodological difficulties. Our aim was to overcome two of these difficulties: the comparability of stimulus material and task in speech versus nonspeech conditions. METHOD In this study, the authors (a) assessed auditory processing of German vowel center stimuli, spectrally rotated versions of these stimuli, and bands of formants; (b) used the same task for linguistic and nonlinguistic conditions; and (c) varied systematically temporal and spectral parameters inherent in the German vowel system. Forty-two adolescents and adults with and without reading disabilities participated. RESULTS Group differences were found for all linguistic and nonlinguistic conditions for both temporal and spectral parameters. Auditory deficits were identified in most but not all participants with dyslexia. These deficits were not restricted to speech stimuli-they were also found for nonspeech stimuli with equal and lower complexity compared with the vowel stimuli. Temporal deficits were not observed in isolation. CONCLUSION These results support the existence of a general auditory processing impairment in developmental dyslexia.

Effects of the Computer-Based Training Program Lautarium on Phonological Awareness and Reading and Spelling Abilities in German Second-Graders

Intact phonological processing abilities are of major importance for successful acquisition of literacy skills. Training studies confirmed that programs which combine phonological training with systematic instruction on letter-sound-relationships are effective in fostering reading and spelling skills. Based on this evidence, we developed the computer-based training program Lautarium for German-speaking primary school children experiencing reading and spelling difficulties. This chapter provides an overview of the structure and contents of Lautarium, and summarizes the empirical evidence concerning the effectiveness of Lautarium-training in children with poor literacy skills. Additionally, we describe a study on the effects of Lautarium-training in two groups of second-graders with relatively low class-level reading skills. Group 1 performed Lautarium-training for a period of 8 weeks at the beginning of second grade, while Group 2 received regular classroom instruction. A significant training effect was found for spelling, but not for phonological awareness or reading. Since only a few children finished the training within the 8-week period, Lautarium was modified in order to allow faster completion of the exercises. Group 2 trained with the modified version at the end of second grade. Subsequent tests revealed stronger improvements in reading, spelling, and phonological awareness in Group 2 when compared to Group 1.

Entwicklung des Lesens und Schreibens

Um verstehen zu konnen, inwiefern die Schriftsprachentwicklung bei Personen mit Lese-Rechtschreibstorung von der von Personen mit unbeeintrachtigtem Lese-Rechtschreiberwerb abweicht, muss zunachst erlautert werden, wie die unbeeintrachtigte Entwicklung des Lesens und Schreibens vor sich geht. Deshalb wird in diesem Kapitel die allgemeine Entwicklung des Lesens und Schreibens behandelt. In Abschn. 2.1. geht es zunachst um die kognitiven Grundlagen des Schriftspracherwerbs. Im Anschluss wird in Abschn. 2.2 anhand des Phasenmodells der Lese-Rechtschreibentwicklung nach Frith (1985, 1986) erlautert, in welchen Phasen die Schriftsprachentwicklung voranschreitet. Abschn. 2.3 zeigt dann anhand der Vorstellung von Modellen des Lesens und Schreibens bei kompetenten/geubten Personen auf, wie Lese- und Rechtschreibprozesse nach Abschluss der Schriftsprachentwicklung ablaufen. Das Kapitel schliest mit einer Darstellung der Entwicklung der Lesesysteme im Gehirn (Abschn. 2.4).