Attention to Pseudo-Tone Melodies Enhances Cortical but Not Brainstem Responses in Humans

Auditory selective attention, the ability to focus on specific sounds while ignoring competitors, enables communication in complex soundscapes. Though attention clearly modulates cortical responses to sound, whether and where this modulation occurs in subcortical structures remains disputed. Here, we use electroencephalography to record cortical and subcortical (auditory brainstem responses, ABRs) activity during a selective attention task. Human participants (18 males, 17 females, 1 of either sex) attend to a 3-note melody in one pitch range presented to one ear while ignoring a competing, interleaved melody in a different pitch range played to the other ear (Laffere et al., 2020, 2021). The melodies consist of pitch-evoking pseudo-tones formed by convolving a periodic impulse train with a brief tone pip. These stimuli allow us to measure both ABRs (elicited by each individual tone pip within a pseudo-note) and cortical responses (elicited by the onsets of pseudo-notes) simultaneously. We observed robust ABRs, but no evidence of modulation by attention. Conversely, cortical responses, measured by event related potentials (ERPs), demonstrated attentional modulation of the P1-N1 peak. We found no evidence that selective attention modulates short-latency auditory brainstem responses under conditions that elicit robust cortical attentional effects.Significance statement Auditory selective attention, which allows us to focus on important sounds while ignoring distractions, is critical for communication in noisy environments. While attention modulates cortical processing of sounds, its effects on subcortical auditory structures are disputed. Using electroencephalography and stimuli engineered to elicit robust cortical and subcortical responses, we measured neural activity in human participants during a selective listening task. Attention enhanced cortical responses to target sounds, while subcortical responses remained unaffected. Together, these results indicate that selective attention to melodies robustly modulates cortical processing but does not measurably affect early brainstem responses.