Structural and functional distinctions between auditory centers revealed with MRI in living humans

From 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.

Department dc:contributor.department

Harvard University--MIT Division of Health Sciences and Technology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Sigalovsky, Irina S., 1972-

Advisor dc:contributor.advisor

• Jennifer R. Melcher.

• Harvard University--MIT Division of Health Sciences and Technology.

Statement dc:rights

• M.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.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/30272
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://dspace.mit.edu/handle/1721.1/30272

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/30272