Mapping the intrinsic functional organization of auditory cortex in individual subjects using 7T MRI Despite countless studies, only broader processing streams of the human auditory cortex (AC) are currently known. The lack of a widely accepted model of human ACs, analogous to that described in non-human primates, has contributed to fundamental theoretical disagreements on sound processing in the human brain. Better understanding of human ACs is crucial for the development of biomarkers and interventions for disorders involving auditory processing deficits and speech and language impairments. Studies of human ACs have been complicated by unique technical barriers, such as their small anatomical scale that hinders fMRI studies at conventional resolutions. However, there are also theoretically important reasons why ACs have been harder to map than other sensory areas: Compared to early visual cortices, human ACs are activated by broader combinations of features and show larger inter-individual variability in anatomy and function. Instead of a feature-specific area only, human ACs could constitute a higher-level processing center, which is needed to support the increasingly complex auditory skills that have evolved in humans only. Achieving a more fundamental understanding of human auditory cognition requires a novel perspective, which considers how human ACs work as a whole and interact with the rest of the human brain. This calls for techniques suited for individual-level studies of dynamic functional networks, instead of group analyses of fMRI localizer data. Unfortunately, to date, such techniques have been lacking. This project combines advanced computational analyses and ultra-high resolution 7T fMRI, to achieve an entirely novel way to characterize the functional organization of human AC in individual subjects. Our proposed work is built on recent revolutionary advances in our laboratories that allow focusing on individual subjects and dynamic functional activity patterns using ultra-high resolution 7T MRI. We will use these novel techniques to study AC activity during (a) the resting state and (b) complex auditory stimulation, and (c) compare the results to the traditional gold standard, tonotopy and bandwidth sensitivity mapping. To precisely map the functional organization of AC in individual subjects, we will use sub-millimeter resolution 7T fMRI, complemented with advanced anatomical MRI analyses of cortical folding patterns, thickness, and intracortical myelin content. fMRI results will be validated using intracranial EEG data from pre-operative patients. These methods will be utilized to localize fine-grained subareas of ACs in individual subjects (Aim 1), characterize AC co-activation patterns that are distributed but stimulus-category specific (Aim 2), and finally to examine the individual variability of the functional arrangement of ACs and compare it to auditory-cognitive abilities (Aim 3).
The exact arrangement of auditory areas in the human cortex remains unknown. This project combines ultra- high field MRI and advanced computational analyses of dynamic functional activity to map the functional arrangement of human ACs at the level of individual subjects with unprecedented resolution and accuracy. The results will advance studies on human auditory function, including a variety of disorders associated with speech perception disorders, language and reading impairments, and other disorders involving dysfunction of auditory cognition.
