Deconstructing the Cortical Sources of Frequency Following Responses to Speech: A Cross-species Approach

Time-varying pitch is a vital cue in the processing of speech signals. Neural processing of time-varying pitch cues in speech has been extensively assayed using scalp-recorded frequency-following responses (FFRs), which are thought to reflect integrated phase-locked activity from neural ensembles exclusively along the subcortical auditory pathway. Emerging evidence however suggests that the auditory cortex contributes to the FFRs as well. However, the response properties and the relative cortical contribution to the scalp-recorded FFR are only beginning to be explored. Here we used direct intracortical recordings from human subjects and animal models (macaque, guinea pig) to deconstruct the cortical sources of FFRs and leveraged representational similarity analysis as a translational bridge to characterize similarities between the human and animal models. We found robust FFRs in the auditory cortex that emerged from the thalamorecepient layers of the auditory cortex and contributed to the scalp-recorded FFRs via volume conduction.