Amplitude envelope onsets and developmental dyslexia: A new hypothesis

Abstract

A core difficulty in developmental dyslexia is the accurate specification and neural representation of speech. We argue that a likely perceptual cause of this difficulty is a deficit in the perceptual experience of rhythmic timing. Speech rhythm is one of the earliest cues used by infants to discriminate syllables and is determined principally by the acoustic structure of amplitude modulation at relatively low rates in the signal. We show significant differences between dyslexic and normally reading children, and between young early readers and normal developers, in amplitude envelope onset detection. We further show that individual differences in sensitivity to the shape of amplitude modulation account for 25% of the variance in reading and spelling acquisition even after controlling for individual differences in age, nonverbal IQ, and vocabulary. A possible causal explanation dependent on perceptual-center detection and the onset-rime representation of syllables is discussed.

Auditory sensory deficits in developmental dyslexia: A longitudinal ERP study

“…On the basis of prior behavioural work (Goswami et al, 2002(Goswami et al, , 2010bHämäläinen et al, 2009;Muneaux et al, 2004;Richardson et al, 2004;Surányi et al, 2009), we expected group effects to be strongest for rise time, however this was not the case. Rather, the most conservative explanation of the ERPs is that children with dyslexia have general differences in auditory neural processing in comparison to children of the same age who do not have dyslexia.…”

“…One possibility that has been widely investigated at the sensory level is that children with dyslexia have auditory processing difficulties (e.g., Tallal, 1980;Witton et al, 1998;Goswami et al, 2002). One auditory sensory deficit that is found in children with dyslexia across languages is inefficient processing of the rate of change of amplitude envelopes (also called rise time; Goswami et al, 2002Goswami et al, , 2010aHämäläinen et al, 2009;Muneaux et al, 2004;Richardson et al, 2004;Surányi et al, 2009). Here, we extend the investigation of rise time processing in dyslexia to the neural level by using EEG.…”

“…This may indicate that the amplitude rise time deficit found in developmental dyslexia is indicative of impairments in distinguishing the different modulation frequency ranges in speech, particularly the lower frequency modulations (around 4 Hz) associated with syllables (see Goswami, 2011). However, rise time is a complex percept, and the behavioural work in dyslexia to date has used linear envelopes rather than the exponential rise times characteristic of natural speech (see Goswami et al, 2002;Richardson et al, 2004). When linear envelopes are used, sounds with more extended rise times have shorter duration steadystates and also take longer to reach peak intensity.…”

Phonological development in relation to native language and literacy: Variations on a theme in six alphabetic orthographies

“…Future work is needed to analyse the association between phonological awareness and speech rhythm more closely. At present, sensitivity to speech rhythm is increasingly being linked to reading progress (e.g., Goswami et al, 2002;Gutierrez-Palma & PalmaReyes, 2008;Holliman et al, 2010). Developmental dyslexics appear less sensitive to the amplitude modulation of the auditory signal at frequencies which, in speech, 5 Note that in this study the sound unit under investigation is confounded with task.…”

“…Notwithstanding this controversy, the evidence is considerable that infant speech perception quickly tunes into the rhythm of native language and that such effects persist in adult speech perception (e.g., Kim, Davis, & Cutler, 2008;Mehler, Dommergues, Frauenfelder, & Segui, 1981;Nazzi, Bertoncini, & Mehler, 1998;Nazzi, Iakimova, Bertoncini, Fredonie, & Alcantara, 2006). Sensitivity to rhythm in speech has recently been identified as a significant predictor of later reading success (e.g., Goswami et al, 2002;Gutierrez-Palma & PalmaReyes, 2008;Holliman, Wood, & Sheehy, 2010). Syllable awareness is one aspect of preschool phonological development that may show evidence of differences in speech rhythm.…”