Seeing speech: visual information from lip movements modifies activity in the human auditory cortex

Neuromagnetic responses were recorded over the left hemisphere to find out in which cortical area the heard and seen speech are integrated. Auditory stimuli were Finnish /pa/ syllables presented together with a videotaped face articulating either the concordant syllable /pa/ (84% of stimuli, V = A) or the discordant syllable /ka/ (16%, V ≠ A). In some subjects the probabilities were reversed. The subjects heard V ≠ A stimuli as /ta/ or /ka/. The magnetic responses to infrequent perceptions elicited a specific waveform which could be explained by activity in the supratemporal auditory cortex. The results show that visual information from articulatory movements has an entry into the auditory cortex.