Atypical right hemisphere response to slow temporal modulations in children with developmental dyslexia

Abstract

Phase entrainment of neuronal oscillations is thought to play a central role in encoding speech. Children with developmental dyslexia show impaired phonological processing of speech, proposed theoretically to be related to atypical phase entrainment to slower temporal modulations in speech (< 10 Hz). While studies of children with dyslexia have found atypical phase entrainment in the delta band (~ 2 Hz), some studies of adults with developmental dyslexia have shown impaired entrainment in the low gamma band (~ 35–50 Hz). Meanwhile, studies of neurotypical adults suggest asymmetric temporal sensitivity in auditory cortex, with preferential processing of slower modulations by right auditory cortex, and faster modulations processed bilaterally. Here we compared neural entrainment to slow (2 Hz) versus faster (40 Hz) amplitude-modulated noise using fNIRS to study possible hemispheric asymmetry effects in children with developmental dyslexia. We predicted atypical right hemisphere responding to 2 Hz modulations for the children with dyslexia in comparison to control children, but equivalent responding to 40 Hz modulations in both hemispheres. Analyses of HbO concentration revealed a right-lateralised region focused on the supra-marginal gyrus that was more active in children with dyslexia than in control children for 2 Hz stimulation. We discuss possible links to linguistic prosodic processing, and interpret the data with respect to a neural ‘temporal sampling’ framework for conceptualizing the phonological deficits that characterise children with developmental dyslexia across languages.

A neural oscillations perspective on phonological development and phonological processing in developmental dyslexia

“…The fNIRs data suggest a different balance of processing for slower versus faster AMs by hemisphere for the two groups, which is driven by atypical responses in both hemispheres. The right hemisphere loci reported by Molinaro et al (2016) and Cutini et al (2016) are also interesting in light of the typical finding of a left-lateralised phonological processing deficit in fMRI studies of dyslexia (functional magnetic resonance imaging, which measures blood flow in the brain and hence identifies which brain areas are most active when different functions are performed; see Richlan, Kronbichler, & Wimmer, 2013, for a meta-analysis). The superior time course information provided by EEG and MEG may explain this discrepancy.…”

An oscillopathic approach to developmental dyslexia: from genes to speech processing

“…Thus, the temporal segmentation of continuous speech via cortical phase-synchronization observed in non-impaired readers is atypically perfomed in dyslexics (Power et al, 2013(Power et al, , 2016Doelling et al, 2014) . Interestingly, differences between dyslexic and non-dyslexic readers in the 2 Hz band response have been found in the right supramarginal gyrus (Cutini et al, 2016) . This brain region is involved in the processing of speech rhythm (Geiser et al, 2008), and speech prosody (Sammler et al, 2015) , and is part of the dorsal stream for speech processing which is thought to be impaired in dyslexics.…”

Reinterpretando la Dislexia. Propuesta diferenciadora para una neurodidáctica inclusiva

“…Con la combinación de las técnicas de neuroimagen y las de emisión de oscilaciones electromagnéticas de los distintos tipos de frecuencia (alfa entre 8-13 Hz, beta entre 12 Hz-30 Hz, gamma entre 25 -100 Hz, delta entre 1-3 Hz y theta 3.5 -7.5 Hz) es posible observar las zonas del cerebro que se activan con distintos tipos de estímulos sonoros y rangos de frecuencia. Las oscilaciones corticales a diferentes tasas temporales produ-cen información acústica relevante para la estructura fonológica del habla, con información de banda delta relacionada con la extracción de patrones de estrés silábico, información de banda theta relacionada con la extracción de información silábica, información de la banda beta relacionada con las unidades de inicio y rima (para dividir una sílaba en unidades lingüísticas de tiempo de inicio, segmento marcado por la vocal) e información de banda baja gamma relacionada con la información fonética (Cutini, Szűcs, Mead, Huss y Goswami, 2016). Los hemisferios están especializados en tipos de frecuencia distintos e interaccionan para integrar la información de las distintas frecuencias.…”

“…El derecho está especializado en oscilaciones delta y theta y el izquierdo en oscilaciones gamma. Como sugieren Cutini et al (2016), las diferencias en la especialización hemisférica encontradas en los disléxicos (Lizarazu, Lallier, Molinaro, Bourguignon, Paz-Alonso et al, 2015; Lehongre, Morillon, Giraud y Ramus, 2013) para las ondas gamma podrían surgir durante el aprendizaje de la asociación grafema-fonema, cuando se está integrando en las representaciones fonológicas neurales, es decir, puede deberse a un efecto compensatorio, por lo que podría ser una consecuencia y no la causa de la pobre conciencia fonológica en disléxicos.…”