![]() ![]() However, because the waves are so rapid, and the signal-to-noise ratio (SNR) so low, the ABR must be measured by presenting thousands of repeated punctate stimuli. Individual waves have been tied to activity in specific parts of the ascending pathway: Wave I (∼2-ms latency) is driven by auditory nerve activity, Wave III (∼4 ms) by the cochlear nucleus, and Wave V (∼6 ms) principally by the lateral lemniscus ( Møller et al., 1995). The potential comprises components referred to as waves, given Roman numerals I–VII according to their latency. In humans, the primary method for measuring activity in subcortical nuclei is the auditory brainstem response (ABR): a highly stereotyped scalp potential in the first ∼10 ms following a very brief stimulus such as a click, recorded through electroencephalography (EEG Burkard et al., 2006). Far from being relays, these subcortical nuclei perform a dazzling array of important functions, from sound localization ( Grothe and Pecka, 2014) to vowel coding ( Carney et al., 2015), making their function essential to understand. ![]() When speech enters the ear and is encoded by the cochlea, it goes on to be processed by an ascending pathway that spans the auditory nerve, brainstem, and thalamus before reaching the cortex. The use of naturally uttered speech to measure the ABR allows the design of engaging behavioral tasks, facilitating new investigations of the potential effects of cognitive processes like language and attention on brainstem processing. Because this method yields distinct peaks that recapitulate the canonical ABR, at latencies too short to originate from the cortex, the responses measured can be unambiguously determined to be subcortical in origin. We found a high degree of morphological similarity between the speech-derived ABRs and the standard click-evoked ABR, in particular, a preserved Wave V, the most prominent voltage peak in the standard click-evoked ABR. In this study we developed and tested a new way to measure the auditory brainstem response (ABR) to ongoing, naturally uttered speech, using EEG to record from human listeners. Instead, experiments have used thousands of repetitions of simple stimuli such as clicks, tone-bursts, or brief spoken syllables, with deviations from those paradigms leading to ambiguity in the neural origins of measured responses. While encoding of continuous natural speech has been successfully probed in the cortex with neurophysiological tools such as electroencephalography (EEG) and magnetoencephalography, the rapidity of subcortical response components combined with unfavorable signal-to-noise ratios signal-to-noise ratio has prevented application of those methods to the brainstem. Speech is an ecologically essential signal, whose processing crucially involves the subcortical nuclei of the auditory brainstem, but there are few experimental options for studying these early responses in human listeners under natural conditions. ![]()
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