Despite the rapid scientific progress during the past decades, the functional architecture of human auditory system still remains elusive. The difficulty of identifying human auditory cortex (AC) subregions has contributed to fundamental theoretical disagreements on sound processing. At the same time, numerous individuals experience attention and auditory processing difficulties that significantly hamper their everyday function. Elucidating human auditory system functional architecture has, thus, both scientific and public health significance. In previous animal models, boundaries of AC fields, subregions sensitive to distinct sound features, have been identified based on reversals of tonotopic (or cochleotopic) gradients. Unfortunately, in humans, the corresponding AC-field boundaries have been difficult to outline in vivo. In comparison to visual cortex subfields, many of which can be almost routinely identified using functional MRI (fMRI) localizer tasks, the putative AC subregions are very small. The AC field boundaries are, thus, easily blurred when conventional imaging resolutions (3-6 mm isotropic voxels) are being utilized. This research program utilizes recent advances in ultra-high field (7T) fMRI techniques to localize human AC fields at higher resolution and accuracy than previously achieved. Previous fMRI studies have been complicated by factors that bias the measured blood-oxygen level dependent (BOLD) signal away from the original site of the neuronal activity. A significant source for such confounds are the large draining vessels near the cortical surface. We apply a novel laminar surface-based fMRI analysis method to avoid biases from pial vessels, combined with surface-based anatomical registration methods that will improve inter-subject analyses (Aim 1). Further, we will delineate the boundaries of AC core region using myelin-weighted anatomical MRI (Aim 2). The results of Aims 1 and 2 will be combined to create a probabilistic model of human AC. In this proposal, we will apply a novel laminar surface-based fMRI analysis method to investigate the functional anatomy of human auditory cortex at considerably higher resolution and accuracy than previously possible. This will help achieve a more advanced system-level understanding of sound processing in the human brain. Although the participants will be healthy subjects, the results will likely help advance studies on a variety of disorders associated with deficits in auditory perception.
This project uses novel functional neuroimaging methods to localize subregions of human auditory cortex, the brain region underlying hearing and sound perception, at higher resolution than previously achieved. Although the participants will be healthy subjects, the results will likely help advance studies on a variety of disorders associated with difficulties in sound perception. Our scientific results may also help develop speech- detection algorithms as well as techniques for hearing aids and prosthetics.
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