Search

Summary: Introduction: In Jyväskylä Longitudinal Study of Dyslexia, we have investigated neurocognitive processes related to phonology and other risk factors of later reading problems. Here we review studies in which we have investigated whether dyslexic children with familial risk background would show atypical auditory/speech processing at birth, at six months and later before school and at school age as measured by brain event-related potentials (ERPs), and how infant ERPs are related to later pre-reading cognitive skills and literacy outcome. Patients and methods: One half of the children came from families with at least one dyslexic parent (the at-risk group), while the other half belonged to the control group without any familial background of dyslexia. Results: Early ERPs were correlated to kindergarten age phonological processing and letter-naming skills as well as phoneme duration perception, reading and writing skills at school age. The correlations were, in general, more consistent among at-risk children. Those at-risk children who became poor readers also differed from typical readers in the infant ERP measures at the group level. ERPs measured before school and at the 3rd grade also differed between dyslexic and typical readers. Further, speech perception at behavioural level differed between dyslexic and typical readers, but not in all dyslexic readers. Conclusions: These findings suggest persisting developmental differences in the organization of the neural networks sub-serving auditory and speech perception, with cascading effects on later reading related skills, in children with familial background for dyslexia. However, atypical auditory/speech processing is not likely a sufficient reason by itself for dyslexia but rather one endophenotype or risk factor. [ABSTRACT FROM AUTHOR]

Abstract: The primary goal of this paper is to improve the classification of multi-channel evoked potentials (EPs) by introducing a temporal domain artifact detection strategy and using this strategy to (a) evaluate how the performance of classifiers is affected by artifacts and (b) show how the performance can be improved by detecting and rejecting artifacts in offline and real-time classification experiments. Using a pattern recognition approach, an artifact is defined in this study as any signal that may lead to inaccurate classifier parameter estimation and inaccurate testing. The temporal domain artifact detection tests include: a within-channel standard deviation (STD) test that can detect signals with little or abnormal variations in each channel and also detect faulty channels, a within-channel clipping (CL) test to detect amplitude clipped EPs in each channel, and a multi-channel EP median distance (MC-MED) test to detect atypical signals not identified by the STD and CL tests. Because the MC-MED test is class-dependent, a novel “pre-testing” approach is developed to identify artifacts in real-time classification experiments. The performance of the artifact detection strategy is demonstrated on real single-trial EP ensembles and it is shown that the strategy is quite effective in identifying atypical EPs. In order to demonstrate the effects of artifacts on classifier performance, a series of classification experiments are designed using a multi-channel decision fusion classification algorithm. Specifically, the classification performance is evaluated on (a) real EP ensembles with artifact contaminations in the training and test sets and (b) ensembles that are free of artifacts in both the training and test sets. It is shown that the improvement in classification accuracy through the incorporation of the artifact detection strategy can be quite significant in real-time classification trials. Furthermore, the generalized formulation of the artifact rejection classification strategy makes it adaptable to various other problems involving the multi-class classification of multivariate signals of multiple sensors. [Copyright &y& Elsevier]

Abstract: Objective: The purpose of the present study was to investigate whether children with reading disabilities (RD) process rise time and pitch changes differently to control children as a function of the interval between two tones. Methods: Children participated in passive oddball event-related potential (ERP) measurements using paired stimuli. Mismatch negativity (MMN), P3a and late discriminative negativity (LDN) responses to rise time and pitch changes were examined. Results: Control children produced larger responses than children with RD to pitch change in the P3a component but only when the sounds in the pair were close to each other. Compared to children with RD, MMN was smaller and LDN larger in control children in response to rise time change when the sounds in the pair were further apart. The non-overlap in ERP measures between the groups was 40–50%. Conclusions: Problems in rapid processing of pitch change were reflected in a component associated with attention switching while amplitude envelope processing problems were reflected in components associated with stimulus detection or discrimination. Significance: Children with RD process both rise time and pitch changes differently from control children thus providing evidence for the nature of amplitude envelope processing and rapid auditory processing deficits in dyslexia. [Copyright &y& Elsevier]

Abstract: Objective: The effects of within stimulus presentation rate and rise time on basic auditory processing were investigated in children with reading disabilities and typically reading children. Methods: Children with reading disabilities (RD; N =19) and control children (N =20) were studied using event-related potentials (ERPs). Paired stimuli were used with two different within-pair-intervals (WPI; 10 and 255ms) and two different rise times (10 and 130ms). Each stimulus was presented with equal probability and long between-pair inter-stimulus intervals (1–5s). The study focused on N1 and P2 components. Results: The P2 responses to the first tone in the pair showed differences between children with RD and control children. Also, children with RD had larger N1 response than control children to stimuli with short WPI and long rise time. Conclusions: These results provide evidence for basic auditory processing abnormalities in children with RD. This processing difference could be related to extraction of stimulus features from sounds or to attentional mechanisms. Significance: Our results show support for behavioral findings that children with RD and control children process rise times differently. More than half of children with RD showed atypical auditory processing. [Copyright &y& Elsevier]