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Larissa McKetton, Kevin DeSimone, Keith Schneider; Population receptive field mapping and tractography in people with absolute pitch.. Journal of Vision 2016;16(12):473. doi: 10.1167/16.12.473.
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© 2017 Association for Research in Vision and Ophthalmology.
Introduction As the spatial resolution of functional magnetic resonance imaging (fMRI) has advanced, recent studies have been able to establish tonotopic mapping in the human auditory cortex. However, there still remains a debate of where the exact orientation of primary gradients occur in Heshl's gyrus leading to various interpretations. In our study we used fMRI to measure the population receptive fields (pRFs) in the auditory cortex to investigate underlying differences in sensory processing in absolute pitch (AP) possessors compared to age and gender matched controls. Tractography was also performed using diffusion MRI to investigate differences in connectivity in the auditory and visual structures. Methods Each participant had their cortex scanned at 1.5 ' 1.5 ' 2 mm3 resolution using a Siemens Trio 3T MRI scanner and 32-channel head coil. Our stimulus consisted of pure tone logarithmic chirps that enabled tonotopic and tuning width mapping of cortical regions. We analyzed the data using an adaptation of the population receptive field (pRF) technique developed by Dumoulin and Wandell (2008), used initially for retinotopic mapping of the visual cortex. Our model treated the pRF underlying each voxel's response as a one-dimensional Gaussian function of frequency providing an estimated sensitivity function for each voxel with a preferred frequency and tuning bandwidth. Diffusion tensor imaging (DTI) scans were acquired with 64 diffusion directions and tractography was performed. Results Both centre frequency and tuning width information was derived from the 1D pRF Gaussian models and plotted on the unfolded cortical surface for each hemisphere in each subject. We were able to obtain reliable tonotopic and tuning bandwidth maps as well as find differences in connectivity in humans with AP compared to controls. Conclusions Our data has helped reveal the variability and consistencies of multi-sensory processing pathways in people with AP compared to normal controls.
Meeting abstract presented at VSS 2016
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