Cerebral Cortex Advance Access originally published online on February 2, 2005
Cerebral Cortex 2005 15(10):1524-1534; doi:10.1093/cercor/bhi031
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Auditory Evoked Potential Patterns to Voiced and Voiceless Speech Sounds in Adult Developmental Dyslexics with Persistent Deficits
1 INSERM EMI-U 9926, Faculté de Médecine, Marseilles, France, 2 INSERM U455, Hôpital Purpan, Toulouse, France and 3 Hôpital La Timone, Department of Pediatric Neurology, Marseilles, France
Address correspondence to Catherine Liégeois-Chauvel, INSERM EMI U9926, Laboratoire de Neurophysiologie et Neuropsychologie, Faculté de Médecine, 27, Bd Jean Moulin, 13005 Marseille, France. Email: Catherine.liegeois{at}medecine.univ-mrs.fr.
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.
Key Words: auditory evoked potentials • categorical perception • dyslexia • speech • voice onset time (VOT)
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