Identifying the relationship between oscillatory dynamics and event-related responses.

Event related potentials (ERPs) and time frequency analysis of the EEG can identify the temporally distinct coordination of groups of neurons across brain regions during sentence processing. Although there are strong arguments that ERP components and neural oscillations are driven by the same changes in the neural signal, others argue that the lack of clear associations between the two suggests oscillatory dynamics are more than just time frequency representations of ERP components, making it unclear how the two are related. The current study seeks to examine the neural activity underlying auditory sentence processing of both semantic and syntactic errors to clarify if ERP and time frequency analyses identify the same or unique neural responses. Thirty-nine adults completed an auditory semantic judgment task and a grammaticality judgment task. As expected, the semantic judgment task elicited a larger N400 and greater increase in theta power for semantic errors compared to correct sentences and the syntactic judgment task elicited a greater P600 and beta power decrease for both grammatical error types compared to syntactically correct sentences. Importantly, we identified a significant relationship between the N400 and P600 ERPs and theta and beta oscillatory dynamics during semantic and syntactic processing. These findings suggest that ERPs and neural oscillations measure similar neural processes; however, unaccounted for variance may indicate that neural oscillations provide additional information regarding fluctuations in power within a given frequency band. Future studies that vary semantic and syntactic complexity are necessary to understand the cognitive processes that are indexed by these oscillations.