CORTICOTHALAMIC MECHANISMS OF HUMAN AUDITORY SELECTIVE ATTENTION

Selective auditory attention allows humans to focus on a relevant sound stream while ignoring competing noise; however, the neural mechanisms underlying this capacity remain poorly understood. Animal studies have provided evidence for distinct corticothalamic loops relevant for spectral (frequency-based) versus temporal (time-based) attention, but whether such loops are also present in humans remains unknown due to methodological constraints, including limited access to thalamic nuclei and insufficient spatial resolution to resolve cortical layers. To address this, we employ a multimodal approach combining ultra-high field fMRI with intracranial EEG (iEEG) recordings. Participants performed an auditory attention task that manipulated the attended tone frequency (low vs. high) and temporal modulation rate (slow vs. fast). Using this paradigm, we map laminar-specific responses in auditory cortex (Heschl’s gyrus) and in subcortical nuclei, including the medial geniculate body (MGB) and inferior colliculus. With population receptive field (pRF) modelling, we characterise tonotopic and temporal tuning profiles across cortical depths and subcortical structures. Ongoing iEEG data collection is expected to provide temporally precise insights into feedforward and feedback dynamics across cortical layers. Pilot 7T fMRI results show reliable tonotopic maps and amplitude modulation rate preference across deep, middle, and superficial cortical layers. Subcortically, frequency-specific responses were observed in both MGB and inferior colliculus, with MGB responses allowing segregation into ventral and dorsal divisions. Preliminary evidence additionally suggests attention-related shifts in frequency preference. These findings demonstrate the feasibility of characterising corticothalamic loops at the level of circuits and laminar processing, aiming to improve our understanding of auditory attention.