UC Irvine

A neural response can be recorded from the scalp that follows ongoing fluctuations in speech energy. This response has been labelled cortical “entrainment”, and while a number of theoretical proposals have been offered regarding the functional role of cortical entrainment in speech perception, the degree to which cortical entrainment reflects peripheral vs. central representations of speech, and acoustic vs. linguistic processes remains unclear. First, we show that the entrainment response reflects differential attentional weights applied across auditory frequency channels, suggesting the entrainment response follows fluctuations in speech within peripheral frequency channels. Second, we show that the strength of the entrainment response to natural fluctuations in speech energy does not depend on whether or not the speech is intelligible, suggesting that the response reflects primarily acoustic rather than linguistic processes. Third, we show that with unnaturally periodic speech stimuli, an entrainment response follows changes in hierarchically-organized levels of linguistic information, independent of acoustic energy, suggesting that under certain conditions, the entrainment response reflects linguistic processes. However, we observe the same entrainment response to hierarchically-organized levels of musical information, suggesting that the cortical processes underlying this entrainment response are not necessarily specific to speech. Together, these results suggest that cortical entrainment can reflect both peripheral and central processes, and that these processes may not be unique to speech.