| |
Abstract:
One crucial aspect of understanding a sentence is to analyze
and integrate semantic information provided by individual words
into an evolving internal meaning representation. In well-formed
sentences, this expectancy is strengthened as more words are being
processed. Evidence for this comes from ERP studies (N400) in
semantically anomalous sentences. Effects of semantic anomaly are
often confounded with effects of probability of coocurrence. Using
visual lexical decision in event-related fMRI, we presented
strongly biasing sentence fragments. Sixty sentence fragments were
each combined with four types of completions. Fragments had a cloze
probability of at least 75% and consisted of a noun (e.g. 'the
author') and a verb (e.g., 'writes'). Completions consisted of
highly probable words ('the book'), improbable but conceivable
words (e.g., 'the speech'), a semantic violation ('the night'), and
pseudowords (e.g. 'the foop'). The task was to read the sentence
and the completion, and to decide whether the completion contained
a word or a pseudoword. Single subject data showed significant
activation in the left inferior frontal gyrus, left middle temporal
gyrus, left precuneus, and right inferior parietal cortex in both
the improbable and the anomalous completions, when compared to the
highly probable completions. The difference between those two types
of unexpected completions was not significant in these areas. These
results suggest that semantic violation might be explained in part
by low probability of coocurrence.
|
