Task-modulated “what” and “where” pathways in human auditory cortex

TLDR

Human neuroimaging studies suggest that localization and identification of relevant auditory objects are accomplished via parallel parietal‑to‑lateral‑prefrontal “where” and anterior‑temporal‑to‑inferior‑frontal “what” pathways, respectively. The study aimed to determine whether these dual pathways already exist in human nonprimary auditory cortex and whether selective attention modulates them in a feature‑specific manner. Using combined fMRI and MEG, the authors examined response adaptation to phonetic versus spatial sound changes in nonprimary auditory cortex. They found a double dissociation in adaptation to phonetic versus spatial changes, with the posterior “where” pathway activating ~30 ms earlier than the anterior “what” pathway, and selective attention modulating each pathway’s response in a feature‑specific way, indicating enhanced tuning of task‑relevant neuronal populations.

Abstract

Human neuroimaging studies suggest that localization and identification of relevant auditory objects are accomplished via parallel parietal-to-lateral-prefrontal “where” and anterior-temporal-to-inferior-frontal “what” pathways, respectively. Using combined hemodynamic (functional MRI) and electromagnetic (magnetoencephalography) measurements, we investigated whether such dual pathways exist already in the human nonprimary auditory cortex, as suggested by animal models, and whether selective attention facilitates sound localization and identification by modulating these pathways in a feature-specific fashion. We found a double dissociation in response adaptation to sound pairs with phonetic vs. spatial sound changes, demonstrating that the human nonprimary auditory cortex indeed processes speech-sound identity and location in parallel anterior “what” (in anterolateral Heschl’s gyrus, anterior superior temporal gyrus, and posterior planum polare) and posterior “where” (in planum temporale and posterior superior temporal gyrus) pathways as early as ≈70–150 ms from stimulus onset. Our data further show that the “where” pathway is activated ≈30 ms earlier than the “what” pathway, possibly enabling the brain to use top-down spatial information in auditory object perception. Notably, selectively attending to phonetic content modulated response adaptation in the “what” pathway, whereas attending to sound location produced analogous effects in the “where” pathway. This finding suggests that selective-attention effects are feature-specific in the human nonprimary auditory cortex and that they arise from enhanced tuning of receptive fields of task-relevant neuronal populations.