Maximizing the efficiency of listening effort is a critical goal for hearing rehabilitation. The current study evaluates modulations in brain functions underlying semantic processing in easier versus more challenging listening conditions. Event-related brain potentials (ERPs) present an ideal methodology for evaluating changes in neural processes as a function of listening effort. Neural processes underlying semantics, indexed by the N400, were elicited by final words of sentences with higher compared to lower likelihood of completing a sentence. Participants were required to respond with longer (1000ms), middle (700ms), or shorter (400ms) response time deadlines (RTDs). Thirty-six typical adults completed the paradigm. Response accuracy was greater for longer RTDs compared to middle and shorter RTDs. Additionally, accuracy was higher for final words that were more predictable compared to words that were less predictable. Additionally, N400 peak latencies were longer for the middle and shorter RTDs compared to the longer RTD, specifically for the words that were less likely to complete the sentence. This approach utilizes an index of semantics, the N400, as the marker of LE. The delayed N400 response is thought to reflect the increased listening effort for more challenging conditions and may result from the increased cognitive demands associated with greater listening effort.
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