distribution over the scalp, which, together with their similar polarity and latency, seems to
indicate that they reflect qualitatively similar processes.
To further test this hypothesis, Patel and collaborators^81 conducted an experiment directly
aimed at comparing the P600 components elicited by harmonic and syntactic violations. ERPs
associated with a word within a grammatically simple, complex, or incorrect sentence were
compared to those associated with the presentation of a chord that belonged to the tonality
induced by the chord sequence, a nearby, or a distant tonality. Results showed that aside from
early morphologic differences in the ERPs to words and chords, due to the differences in the
acoustic characteristics of these two types of auditory signals, the effects associated with the284 Figure 18.6Overlapped are the ERPs to congruent and incongruent endings, recorded at the central recording
site (Cz), when participants paid attention only to the language (left column) or only to the music (right column)
of the opera’s excerpts. A large N400 effect is generated when participants focus their attention on language. This
effect completely vanishes when attention is focused on music (top row). Similarly, the P600 effect is much greater
when participants paid attention to music than when they paid attention to language (medium row). Finally, when
words are both semantically incongruous and sung out of tune, the N400 effect is greater when participants paid
attention to the language, and the P600 effect is greater when they paid attention to the music (bottom row). (From
Regnault and Besson, in preparation.)
SemanticMusicalBothP600P600N400N4000 400 1000 0
Congruous
Incongruous400 1000 ms- 2 μV
Attention to language Attention to music