Auditory Evoked Potential Patterns to Voiced and Voiceless Speech Sounds in Adult Developmental Dyslexics with Persistent Deficits

Abstract

Auditory evoked potentials (AEPs) were recorded from eight developmental dyslexic adults with persistent reading, spelling and phonological deficits, and 10 non-dyslexic controls to voiced (/ba/) and voiceless (/pa/) consonant-vowel syllables. Consistent with previous data, non-dyslexics coded these stimuli differentially according to the temporal cues that form the basis of the voiced/voiceless contrast: AEPs had time-locked components with latencies that were determined by the temporal structure of the stimuli. Dyslexics were characterized by one of two electrophysiological patterns: AEP pattern I dyslexics demonstrated a differential coding of stimuli on the basis of some temporal cues, but with an atypically large number of components and a considerable delay in AEP termination time; AEP pattern II dyslexics demonstrated no clear differential coding of stimuli on the basis of temporal cues. These data reveal the presence of anomalies in cortical auditory processing which could underlie persistent perceptual and linguistic impairments in some developmental dyslexics. Furthermore, scalp AEP distribution maps showing the difference observed between /ba/ and /pa/ activity over time suggest that the regions implicated in the processing of crucial time-related acoustic cues were not systematically lateralized to the left hemisphere like they were for non-dyslexics. These findings may be conducive to a better understanding and treatment of perceptual dysfunctions in developmental language disorders.

Pre-attentive Spectro-temporal Feature Processing in the Human Auditory System

“…In attentive processing, we demonstrated in a previous study a clear asymmetrical response pattern favouring the left posterior supratemporal plane during the attentional processing of temporal features in speech and non-speech sounds (Zaehle et al 2007a). Similarly, EEG and MEG studies (Giraud et al 2005;Sieroka et al 2003), and intracerebral recordings (Liegeois-Chauvel et al 1999) demonstrated an enhanced performance of the left compared to the right auditory cortex during the processing of temporal acoustic information.…”

Objective measurement of high-level auditory cortical function in children

“…We assume that the measured response reflects the sum of neural activity from the cortex rather than the auditory brainstem, given the low modulation frequency selected. Further, we have suggested that the cortical response for the AM-BBN alone is elicited by the onset of the stimulus [67][68][69] but that the response elicited by the AM-BBN following the BBN is elicited by the temporal change in the stimulus and represents an acoustic change complex (ACC). Consistent with this interpretation is that the cortical responses (and N2 latencies) are similar when elicited by the AM-BBN stimulus alone in the two extreme modulation conditions (100% compared with 0%).…”

Gaps-in-noise (GIN©) test results in children with and without reading disabilities and phonological processing deficits

“…It is perhaps the most common and most carefully studied neurobehavioral disorder affecting children, with reported prevalence rates ranging from 5% to 17% (Shaywitz et al, 1990;Lyon, 1995;Shaywitz, 1998;Giraud et al, 2005). Moreover, it is a neurobiological condition that reportedly affects approximately 80% of all individuals identifi ed as learning disabled (Bell et al, 2003;Shaywitz et al, 2007).…”