W. Deimel

Auditory processing and dyslexia: evidence for a specific speech processing deficit

IN order to investigate the relationship between dyslexia and central auditory processing, 19 children with spelling disability and 15 controls at grades 5 and 6 were examined using a passive oddball paradigm. Mismatch negativity (MMN) was determined for tone and speech stimuli. While there were no group differences for the tone stimuli, we found a significantly attenuated MMN in the dyslexic group for the speech stimuli. This finding leads to the conclusion that dyslexics have a specific speech processing deficit at the sensory level which could be used to identify children at risk at an early age.

Speech perception deficit in dyslexic adults as measured by mismatch negativity (MMN)

Deficits in phonological processing are known to play a major role in the aetiology of dyslexia, and speech perception is a prerequisite condition for phonological processing. Significant group differences between dyslexics and controls have been found in the categorical perception of synthetic speech stimuli. In a previous work, we have demonstrated that these group differences are already present at an early pre-attentive stage of signal processing in dyslexic children: the late component of the MMN elicited by passive speech perception was attenuated in comparison to a control group. In this study, 12 dyslexic adults and 13 controls were assessed using a passive oddball paradigm. Mismatch negativity (MMN) was determined for both tone and speech stimuli. The tone stimuli yielded two MMN components, but no group differences. Three components were found for the speech stimuli. Multivariate testing for group differences yielded a significant result, and univariate P values revealed significant differences between dyslexics and controls in two of the three time windows. This suggests that speech perception as measured on an early, pre-attentive level plays a major role in dyslexia not only in children (as shown in our previous study) but also in adults.

The role of phonological awareness, speech perception, and auditory temporal processing for dyslexia

There is strong evidence that auditory processing plays a major role in the etiology of dyslexia. Auditory temporal processing of non-speech stimuli, speech perception, and phonological awareness have been shown to be influential in reading and spelling development. However, the relationship between these variables remains unclear. In order to analyze the influence of these three auditory processing levels on spelling, 19 dyslexic and 15 control children were examined. Significant group differences were found for all speech variables, but not for any non-speech variable. Structural equation modeling resulted in a fairly simple model with direct paths to the respective next lower level. One additional path from preattentive speech processing to spelling had to be included in order to improve the model fit. These results strengthen the role of speech and phonological processing for the etiology in dyslexia.

Pre-attentive processing of auditory patterns in dyslexic human subjects

It has been hypothesized that auditory temporal processing plays a major role in the aetiology of dyslexia. Event-related brain potentials (mismatch negativity, MMN) of auditory temporal processing were assessed in 15 dyslectic adults and 20 controls. A complex tonal pattern was used where the difference between standard and deviant stimuli was the temporal, not the frequency structure. Dyslexics had a significantly smaller MMN in the time window of 225-600 ms. This result shows that dyslexics have a significant pre-attentive deficit in processing of rapid temporal patterns suggesting that it may be the temporal information embedded in speech sounds, rather than phonetic information per se, that resulted in the attenuated MMN found in dyslexics in previous studies. MMN scalp topographies were similar for both groups, showing a maximum over fronto-central leads.

Role of auditory temporal processing for reading and spelling disability.

The role of auditory temporal processing in reading and spelling was investigated in a sample of 30 children and one of 31 adults, using a gap-detection task with nonspeech stimuli. There was no evidence for a relationship between reading and spelling disability (dyslexia) and the gap-detection threshold. The results were discussed regarding the relevance for the popular hypothesis of an auditory temporal processing deficit underlying dyslexia.

Developmental Dyslexia – Recurrence Risk Estimates from a German Bi-Center Study Using the Single Proband Sib Pair Design

Objective: Several studies have demonstrated a genetic component for dyslexia. However, both segregation and linkage analyses show contradictory results pointing at the necessity of an optimal ascertainment scheme for molecular genetic studies. Previously, we have argued that the single proband sib pair design (SPSP) would be optimal. The aims of this paper therefore are to demonstrate the practicability of the SPSP design and the estimation of recurrence risks for reading and writing. Methods: We assessed spelling and reading in a family sample ascertained through the SPSP design. 287 families with at least two siblings and their parents were recruited. At least one child was affected with spelling disorder according to a one standard deviation (1SD) discrepancy criterion. Results: Mean values for probands and their siblings were different for both the spelling and the reading phenotype. For the probands, variances of the phenotype spelling were smaller. These effects became stronger with more extreme selection criteria. Both siblings fulfilled the 1SD criterion for spelling and reading in 60.3 and 28.9% of the families, respectively, indicating a low cost efficiency of the double proband sib pair approach. A recurrence risk of 4.52 (CI: 4.07–4.93) was obtained for spelling when the 1SD criterion was applied to both siblings. Recurrence risk estimates were similar for reading. Conclusion: The study demonstrates the suitability of the SPSP design for genetic analysis of dyslexia. The recurrence risk estimates may be used for determining sample sizes in gene mapping studies.

Motion-onset VEPs in dyslexia. Evidence for visual perceptual deficit.

The magnocellular deficit theory is one of the prominent theories in dyslexia. However, recent studies have produced conflicting results. In order to assess the validity of this theory, 8 dyslexic children and 14 controls were examined with a motion-onset visual evoked potential (VEP) paradigm at three different velocities (2, 8, and 16 deg/s). VEP elicited by stationary gratings served as a control condition. Amplitudes of motion-onset VEP components (P100, P200) but not of the stationary VEP are significantly attenuated in dyslexic children. Further, there is an interaction of group and velocity for the P200 in the way that group differences are more pronounced for higher velocities than for lower velocities. These results support the hypothesis of an impairment of a specific magnocellular function in dyslexia.

Zur Diagnostik der Lese- Rechtschreibstörung

Zusammenfassung: Das ICD-10 fordert fur die klinische Diagnose der Lese-Rechtschreibstorung die Verwendung von Tabellen, die die Korrelation von Rechtschreibung bzw. Lesen und Intelligenz berucksichtigen (Regressionsmodell). Im vorliegenden Beitrag werden die Konsequenzen fur die Interpretation psychometrischer Tests zur Diagnostik der Lese-Rechtschreibstorung erortert. Auserdem wird eine Tabelle vorgestellt, mit Hilfe derer diagnostische Entscheidungen unter Berucksichtigung des Regressionsmodells getroffen werden konnen. Daruber hinaus wird eine Abschatzung der zu erwartenden Pravalenz auf Grund einer Computer-Simulation mitgeteilt.

Interrelationship and Familiality of Dyslexia Related Quantitative Measures

Dyslexia is a complex gene‐environment disorder with poorly understood etiology that affects about 5% of school‐age children. Dyslexia occurs in all languages and is associated with a high level of social and psychological morbidity for the individual and their family; approximately 40‐50% have persistent disability into adulthood. The core symptoms are word reading and spelling deficits, but several other cognitive components influence the core phenotype.

Visual evoked potentials elicited by coherently moving dots in dyslexic children

The magnocellular deficit theory is one of the prominent hypotheses in dyslexia research. However, recent studies have produced conflicting results. Ten dyslexic children and 12 controls were examined with visual evoked potentials elicited by random dot kinematogram. The experiment comprises two sequences, one with randomly moving dots (control condition) and a second sequence where a fraction of the dots were moved coherently at the left or right side (depending on the level of coherence, 10%, 20%, and 40% of the dots). Randomly moving dots elicited two components, a P100 and P200, which were not different between the groups. Coherently moving dots elicited a late positivity between 300 and 800 ms, which was significantly attenuated in dyslexic children. The area of this component becomes larger at a higher level of coherence. This study supports the hypothesis of an impairment of a specific magnocellular function in dyslexia.