An event-related brain potential experiment was carried out to investigate the temporal relationship
between lexical selection and the semantic integration in auditory sentence processing. Participants were
presented with spoken sentences that ended with a word that was either semantically congruent or
anomalous. Information about the moment in which a sentence-final word could uniquely be identified,
its isolation point (IP), was compared with the onset of the elicited N400 congruity effect, reflecting
semantic integration processing. The results revealed that the onset of the N400 effect occurred prior to
the IP of the sentence-final words. Moreover, the factor early or late IP did not affect the onset of the
N400. These findings indicate that lexical selection and semantic integration are cascading processes, in
that semantic integration processing can start before the acoustic information allows the selection of a
unique candidate and seems to be attempted in parallel for multiple candidates that are still compatible
with the bottom–up acoustic input.