RESUMEN
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.
Asunto(s)
Encéfalo/fisiopatología , Dislexia/fisiopatología , Potenciales Evocados/fisiología , Lectura , Percepción del Habla/fisiología , Factores de Edad , Encéfalo/crecimiento & desarrollo , Niño , Preescolar , Dislexia/psicología , Humanos , Lactante , Recién Nacido , Estudios Longitudinales , Factores de RiesgoRESUMEN
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.
Asunto(s)
Variación Contingente Negativa/fisiología , Dislexia/fisiopatología , Potenciales Evocados Auditivos/fisiología , Discriminación de la Altura Tonal/fisiología , Tiempo de Reacción/fisiología , Estimulación Acústica/métodos , Mapeo Encefálico , Niño , Electroencefalografía , Femenino , Humanos , Masculino , Análisis Multivariante , Pruebas Neuropsicológicas , Lectura , Factores de TiempoRESUMEN
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 255 ms) and two different rise times (10 and 130 ms). 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.
Asunto(s)
Dislexia/fisiopatología , Potenciales Evocados Auditivos/fisiología , Estimulación Acústica , Análisis de Varianza , Atención , Percepción Auditiva/fisiología , Niño , Electroencefalografía , Femenino , Lateralidad Funcional/fisiología , Humanos , Pruebas de Inteligencia , Masculino , Pruebas Neuropsicológicas , Análisis de Componente Principal , LecturaRESUMEN
Low sensitivity to amplitude modulated (AM) sounds is reported to be associated with dyslexia. An important aspect of amplitude modulation cycles are the rise and fall times within the sound. In this study, simplified stimuli equivalent to just one cycle were used and sensitivity to varying rise times was explored. Adult participants with dyslexia or compensated dyslexia and a control group performed a detection task with sound pairs of different rise times. Results showed that the participants with dyslexia differed from the control group in rise time detection and a correlation was found between rise time detection and reading and phonological skills. A subgroup of participants with lower sensitivity to rise time detection characterized by low accuracy in syllable-level phonological skills was found within the dyslexic group. Short stimuli containing only one rise time produced associations with phonological skills and reading, even in a language where the perception of rise time contrasts are not crucial for the signaling of phonemic contrast.
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Dislexia/fisiopatología , Percepción Sonora , Estimulación Acústica , Adulto , Escritura Manual , Humanos , Reconocimiento Visual de Modelos , Fonética , Tiempo de Reacción , LecturaRESUMEN
The aim of the study was to examine whether a newborn can detect changes in a speech stimulus consisting of a fricative followed by a vowel /su/. In addition, we studied possible effect of the two sleep stages (active and quiet sleep) on the evoked magnetic responses. In young children (6 years), the same stimulus evokes a prominent deflection, consisting of two peaks. The first one (P1m) is evoked by the beginning of the fricative consonant and has a latency of about 145 ms. The second peak (P2m) with a latency of 340 ms, is evoked by the switch to the vowel. In newborns (n = 10), the waveform resembled that of the older children but latencies of the corresponding peaks were longer, 190 and 435 ms, correspondingly. The results suggest that already the newborn brain detects the change inside the auditory speech stimulus, namely the fricative sound changing into a vowel. However, the immaturity of the brain is reflected in the prolonged latencies. In addition, the responses were higher in amplitude in quiet sleep than in active sleep (F (1.9) = 36.5; p < 0.0002). This is in line with the enhanced somatosensory magnetic fields to tactile stimulation in quiet compared to active sleep in newborns.
Asunto(s)
Potenciales Evocados Auditivos/fisiología , Magnetoencefalografía/métodos , Fases del Sueño/fisiología , Acústica del Lenguaje , Percepción del Habla/fisiología , Estimulación Acústica/métodos , Análisis de Varianza , Niño , Femenino , Humanos , Recién Nacido , Masculino , Habla/fisiologíaRESUMEN
Differences revealed by factor scores extracted by principal component analysis (PCA) from event-related potential (ERP) data of newborns with and without familial risk for dyslexia were examined and compared to results obtained by using original averaged ERPs. ERPs to consonant-vowel syllables (synthetic /ba/, /da/, /ga/; and natural /paa/, /taa/, /kaa/) were recorded from 26 at-risk and 23 control 1-7 day-old infants. The stimuli were presented equiprobably and with interstimulus intervals varying at random from 3,910 to 7,285 ms. Statistically significant between-group differences were found to be relatively similar irrespective of the methods of analysis (original ERPs vs. factor scores from PCA). Responses to /ga/ differed from those to /ba/ and /da/ between the groups in the right hemisphere at the latencies of 50-170 ms (Factor 4) and 540-630 ms (Factor 3). The groups differed also in their responses to /da/ in the posterior electrode sites at 740-940 ms (Factor 2). There were no group differences in the natural stimulus set. These results demonstrate that brain activation differences may be implicated in risk for dyslexia immediately after birth. The results also show that the PCA-ANOVA procedure is an effective way of identifying the group-related variance in the ERP-data when the component structure, such as those of infants, is not well-known in advance.