Audiovisual integration of letters in the human brain

Letters of the alphabet have auditory (phonemic) and visual (graphemic) qua lities. To investigate the neural representations of such audiovisual objec ts, we recorded neuromagnetic cortical responses to auditorily, visually, a nd audiovisually presented single letters. The auditory and visual brain ac tivations first converged around 225 ms after stimulus onset and then inter acted predominantly in the right temporo-occipito-parietal junction (280-34 5 ms) and the left (380-540 ms) and right (450-535 ms) superior temporal su lci. These multisensory brain areas, playing a role in audiovisual integrat ion of phonemes and graphemes, participate in the neural network supporting the supramodal concept of a "letter." The dynamics of these functions brin g new insight into the interplay between sensory and association cortices d uring object recognition.