The current study tested the hypothesis that lexical ambiguity, a common source of representational conflict during language comprehension, engages domain-general cognitive control processes that are reflected by theta-band oscillations in scalp-recorded electroencephalograms (EEG). In Experiment 1, we examined the neural signature elicited by lexically ambiguous compared to unambiguous words during sentence comprehension. The results showed that midfrontal theta activity was increased in response to linguistic conflict (lexical ambiguity). In Experiment 2, we examined postconflict adaptation effects by comparing temporarily ambiguous sentences that followed previous instances of conflict (other temporarily ambiguous sentences) to those that followed a previous low-conflict (unambiguous) sentence. A midfrontal theta effect associated with linguistic conflict was again found in Experiment 2, such that theta was increased for temporarily ambiguous sentences that followed previous low-conflict (unambiguous) sentences compared with those that followed previous high-conflict (temporarily ambiguous) sentences. In both experiments, facilitated lexical semantic processing was also observed for words that came after the point of conflict, which may reflect a downstream “benefit” of cognitive control engagement. Overall, our results provide novel insights into the neurocognitive mechanisms underlying conflict processing in language comprehension and suggest that the same neural computations are involved in processing nonlinguistic and linguistic conflict.
