Cross-modal enhancement of the MMN to speech-sounds indicates early and automatic integration of letters and speech-sounds.
Recently brain imaging evidence indicated that letter/speech-sound integration, necessary for establishing fluent reading, takes place in auditory association areas and that the integration is influenced by stimulus onset asynchrony (SOA) between the letter and the speech-sound. In the present study, we used a specific ERP measure known for its automatic character, the mismatch negativity (MMN), to investigate the time course and automaticity of letter/speech-sound integration. We studied the effect of visual letters and SOA on the MMN elicited by a deviant speech-sound. We found a clear enhancement of the MMN by simultaneously presenting a letter, but without changing the auditory stimulation. This enhancement diminishes linearly with increasing SOA. These results suggest that letters and speech-sounds are processed as compound stimuli early and automatically in the auditory association cortex of fluent readers and that this processing is strongly dependent on timing.
Froyen
Dries
D
Department of Cognitive Neuroscience, Faculty of Psychology, University of Maastricht, Maastricht Brain Imaging Center, Maastricht, The Netherlands. d.froyen@psychology.unimaas.nl
Van Atteveldt
Nienke
N
Bonte
Milene
M
Blomert
Leo
L
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010700:Phonetics; D011932:Reading; D013067:Speech Perception / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*