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.

Grant Number: 5R21DC020530-03
NIH Institute/Center: NIH
Principal Investigator: Emily Allen