Hemispheric Asymmetry in Auditory Processing of Speech Envelope Modulations in Prereading Children

Abstract

The temporal envelope of speech is an important cue contributing to speech intelligibility. Theories about the neural foundations of speech perception postulate that the left and right auditory cortices are functionally specialized in analyzing speech envelope information at different time scales: the right hemisphere is thought to be specialized in processing syllable rate modulations, whereas a bilateral or left hemispheric specialization is assumed for phoneme rate modulations. Recently, it has been found that this functional hemispheric asymmetry is different in individuals with language-related disorders such as dyslexia. Most studies were, however, performed in adults and school-aged children, and only a little is known about how neural auditory processing at these specific rates manifests and develops in very young children before reading acquisition. Yet, studying hemispheric specialization for processing syllable and phoneme rate modulations in preliterate children may reveal early neural markers for dyslexia. In the present study, human cortical evoked potentials to syllable and phoneme rate modulations were measured in 5-year-old children at high and low hereditary risk for dyslexia. The results demonstrate a right hemispheric preference for processing syllable rate modulations and a symmetric pattern for phoneme rate modulations, regardless of hereditary risk for dyslexia. These results suggest that, while hemispheric specialization for processing syllable rate modulations seems to be mature in prereading children, hemispheric specialization for phoneme rate modulation processing may still be developing. These findings could have important implications for the development of phonological and reading skills.

Theta, beta and gamma rate modulations in the developing auditory system

“…However, a right processing preference in both groups could only be assumed in the current study based on monaural right ear stimulation. Yet, right processing asymmetry for theta rate modulations was previously demonstrated in adults (Poelmans et al, 2012a,b), children (Abrams et al, 2009;Vanvooren et al, 2014) and even in newborns (Telkemeyer et al, 2009(Telkemeyer et al, , 2011. As such, the functional theta rate processing asymmetry is probably congenital or early-acquired.…”

“…The children were recruited from a large longitudinal study (Vanvooren et al, 2014). Adults were recruited from a population of students.…”

Kalman Filter Based Estimation of Auditory Steady State Response Parameters

“…The model is based on the assumption that each electrode is measuring the same underlying signal but with independent noise, this assumption is not strictly true [24], [25]. However, closely spaced electrodes often show similar amplitude and phase and are combined [11]. For entire scalp analysis, other methods may be more appropriate [13].…”

“…Lastly, no consensus has been made on how best to integrate information from multiple electrodes. Various approaches have been proposed to utilise information from multiple recording electrodes including averaging the signals in the time domain [9], averaging the output statistic [11], spatial filtering [12] and blind source separation [13]. DFT based EASSR analysis has additional shortcomings.…”

Relying on brain rhythms for improving the diagnosis of dyslexia

“…It is also true that gamma phase-synchronization has been reported to be normal before reading onset (De Vos et al, 2017b). However, preliterate children at risk for dyslexia have been found to exhibit an atypical lateralization for this oscillatory frequency band (Vanvooren et al, 2014). Phoneme discrimination has proven to be a confident criterion for differentiating poor and normal reading abilities (Hämäläinen et al, 2009, Brunner, Bäumer, Rosenauer, Scheller, & Plinkert, 2010Groth, Lachmann, Riecker, Muthmann, & Steinbrink, 2011;Steinbrink, Klatter, & Lachmann, 2014), and in fact, this is an ability that emerges very early during language 14 acquisition (Kuhl, 1979;Shahidullah & Hepper, 1994;Cheour-Luhtanen et al, 1995).…”