Neural correlates of semantic competition during processing of ambiguous words

Abstract

The current study investigated the neural correlates that underlie the processing of ambiguous words and the potential effects of semantic competition on that processing. Participants performed speeded lexical decisions on semantically related and unrelated prime-target pairs presented in the auditory modality. The primes were either ambiguous words (e.g., ball) or unambiguous words (e.g., athlete), and targets were either semantically related to the dominant (i.e., most frequent) meaning of the ambiguous prime word (e.g., soccer) or to the subordinate (i.e., less frequent) meaning (e.g., dance). Results showed increased activation in the bilateral inferior frontal gyrus (IFG) for ambiguous-related compared to unambiguous-related stimulus pairs, demonstrating that prefrontal areas are activated even in an implicit task where participants are not required to explicitly analyze the semantic content of the stimuli and to make an overt selection of a particular meaning based on this analysis. Additionally, increased activation was found in the left IFG and the left cingulate gyrus for subordinate meaning compared to dominant meaning conditions, suggesting that additional resources are recruited in order to resolve increased competition demands in accessing the subordinate meaning of an ambiguous word.

Figure 1

Mean RTs (ms) for the related conditions in the lexical decision task. Dominant and subordinate refer to the relationship of the target stimulus to one of the two meanings of the ambiguous prime stimulus (see Table 1, see text).

Figure 2

Mean accuracy (% correct) for the related conditions in the lexical decision task. Dominant and subordinate refer to the relationship of the target stimulus to one of the two meanings of the ambiguous prime stimulus (see Table 1, see text).

Figure 3

Group functional map (N=16) for the Ambiguous Related > Unambiguous Related contrast. Significantly activated clusters shown: left IFG and right MFG (p < .05). Figure 4.

Figure 4

Group functional map (N=16) for the Ambiguous Dominant Related < Ambiguous Subordinate Related contrast. Significantly activated clusters shown: left IFG and left cingulate gyrus (p < .05).