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dc.contributor.advisorJennifer R. Melcher.en_US
dc.contributor.authorSigalovsky, Irina S., 1972-en_US
dc.contributor.otherHarvard University--MIT Division of Health Sciences and Technology.en_US
dc.date.accessioned2008-02-28T16:08:44Z
dc.date.available2008-02-28T16:08:44Z
dc.date.copyright2005en_US
dc.date.issued2005en_US
dc.identifier.urihttp://dspace.mit.edu/handle/1721.1/30272en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/30272
dc.descriptionThesis (Ph. D.)--Harvard University--MIT Division of Health Sciences and Technology, 2005.en_US
dc.descriptionVita.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.description.abstractFrom brainstem to cortex, sound is processed in centers that are functionally and structurally distinct. In animals, invasive electrophysiology and histology has revealed these distinctions and, consequently, organizational principles behind sound processing. In humans, however, comparable demonstrations are sparse. This thesis presents three MRI studies that provide new information regarding structural and functional distinctions between auditory centers in living humans. The first study compared the effect of a fundamental acoustic variable, sound level, on the population neural activity of auditory brainstem, thalamus and cortex. Brainstem and cortex exhibited contrasting sensitivities to sound level (growth in activation followed by saturation in brainstem vs. plateau then growth in cortex), with thalamus showing intermediate properties. The second study identified functional distinctions between cortical areas by spatially mapping the temporal properties of fMRI responses. Using a continuous noise stimulus, we found sustained responses on Heschl's gyrus flanked medially and laterally by more phasic activity. This pattern suggests that transient activity marking the beginning and end of a sound is most pronounced in non-primary areas of auditory cortex. The region of sustained responses may correspond to primary and primary-like areas. Thus, it may present a physiological marker for these areas in neuroimaging studies, something that has long been needed in the auditory neuroimaging field. The third study examined whether auditory cortical areas can be distinguished - in the living human brain - based on classical features of cortical gray matter previously resolvable only in postmortem tissue.en_US
dc.description.abstract(cont.) By mapping the imaging parameter R1, we identified regions of heavily myelinated gray matter that may correspond to primary auditory cortex. We further found greater gray matter myelination of the left temporal lobe, which may be a substrate for higher fidelity temporal processing on the left, and for left-hemispheric speech and language specializations. Being able to resolve gray matter structure in-vivo opens the way to relating cortical physiology and structure directly in living humans in ways previously possible only in animals.en_US
dc.description.statementofresponsibilityby Irina S. Sigalovsky.en_US
dc.format.extent144 p.en_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/30272en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582
dc.subjectHarvard University--MIT Division of Health Sciences and Technology.en_US
dc.titleStructural and functional distinctions between auditory centers revealed with MRI in living humansen_US
dc.typeThesisen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentHarvard University--MIT Division of Health Sciences and Technology
dc.identifier.oclc60847574en_US


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