Revisiting the 40-Hz gamma response: Phase-locked neural activity along the human auditory pathway relates to bilingual experience.

Spoken language experience influences brain responses to sound, but it is unclear whether this neuroplasticity is limited to speech frequencies (>100 Hz) or also affects lower gamma ranges (∼30-60 Hz). Using the frequency-following response (FFR), a far-field phase-locked response to sound, we explore whether bilingualism influences the location of the strongest response in the gamma range. Our results indicate that the strongest gamma response for bilinguals is most often at 43 Hz, compared to 51 Hz for monolinguals. Using a computational model, we show how this group difference could result from differential subcortical activation. These results shed light on the well-known but under-explored variability observed in the gamma range and highlight that FFRs are a composite of neural activity from both subcortical and cortical sources. Additionally, our findings emphasize that individual auditory experiences can uniquely shape subcortical activation, influencing FFRs below speech frequencies.