Functional and structural characterization of human auditory cortex using high resolution MRI

PROJECT SUMMARY A more complete characterization of auditory cortical processing in humans is critical to understanding auditory perception and cognition. Without it, developing effective treatment options for various auditory processing deficits, such as those rooted in central auditory processing, may not be possible. Currently, there is a lack of consensus regarding how to define and parcellate even the earliest regions of auditory cortex, including primary auditory region A1, highlighting the significant gaps in our overall understanding of sound processing. Traditional approaches to defining primary auditory regions in humans include identifying the macroanatomical landmarks known as the Heshl’s gyri (HG) in each hemisphere and using their locations as a rough approximation of A1. While macroscopic anatomical information, such as the sulcal and gyral patterning in auditory cortex, can provide a rough estimate of where primary auditory regions are located, it is not sufficiently accurate. This is likely due to the high degree of variability in the size, shape, location, and number of HGs found in the auditory cortices of humans. Conversely, attempts to use functional properties—in particular, frequency mapping (tonotopy)—have also been met with limited success, as tonotopic gradients cannot be used to uniquely position the areal boundaries of A1. Aim 1 of the proposed research will exploit recent advances in magnetic resonance imaging (MRI) to non-invasively acquire unprecedentedly high-resolution in vivo human anatomical data at the mesoscopic scale (~0.35mm3), revealing biological information that was not previously available via neuroimaging. Access to this information will allow us to generate detailed, data-driven parcellations of auditory cortices that more closely match the underlying cytoarchitecture. Aim 2 will complement the anatomical approaches in Aim 1 by defining A1 in the same set of individuals, using several high-field cortical and sub- cortical measures of functional activation derived using both task-based and functional connectivity paradigms. The task-based functional data will be used to construct tuning maps for several key perceptually-relevant acoustic features, the parcellation of which will be constrained by the patterns of resting state connectivity between sub-cortical and cortical regions. Work from both aims, which includes mesoscopic MRI, subcortical neuroimaging, computational modeling, and resting state connectivity, will be combined to provide the auditory neuroimaging community with a state-of-the-art multimodal structure-function characterization of primary auditory cortex in humans. To aid in the standardization of auditory cortex characterizations in future studies, this information will be made publicly available, along with an atlas. The long-term goal is a complete characterization and parcellation of auditory cortex in humans. The resulting parcellations in normal-hearing populations will serve as a baseline for characterizing and subsequently developing effective treatments for auditory processing deficits in hearing-impaired populations.