Principal Investigator: Robert J. Zatorre
Functional Organization of the Human Auditory Cortex
Neuroimaging techniques have emerged as important tools to explore the structure and function of the human brain in-vivo, allowing detailed and systematic investigations into the neural bases for complex cognitive functions. The general goal of the research in this application is to further our understanding of the functional properties of auditory perceptual and cognitive systems, and their neural substrate. Much remains unknown about the functional architecture of the central auditory nervous system, particularly in the human brain. We propose to study this issue in depth, to explore both basic mechanisms involved in early stages of information processing, as well as higher-order processes that are critical components of perception.
The brain imaging center at the Montreal Neurological Institute provides a unique setting within which to pursue these studies. The availability of state-of-the-art PET and MR imaging systems, together with sophisticated software for image processing and statistical analysis is crucial to the proposed research. Most important is the environment itself, within which investigators with diverse backgrounds, interests and skills come together to work on problems which bear on each other, sometimes in unexpected ways.
Our specific aims are as follows:
(1) To test the hypothesis that the auditory cortices within each hemisphere differ in their functional organization, such that there is a tradeoff between rate of temporal integration and spectral resolution. PET studies will examine the slope of CBF change as a function of rate of stimulus presentation and frequency spacing. We predict that the left auditory cortex will respond most consistently to increasing rate of stimulation, whereas the fight will be most sensitive to increasing frequency spacing. These studies will provide basic information regarding hemispheric differences in the functional response properties of the auditory cortex, which will be relevant to models of the perception of speech and musical sounds.
(2) To develop novel MU procedures that should minimize the effects of
acoustic artifact on the response of the auditory cortex to a stimulus
of interest, and to validate this approach by a formal, systematic comparison
between fMRI and PET data with the same subject sample, using a variety
of auditory stimuli. These studies will allow us to optimize fMRI techniques
such that in future years we will be able to study auditory cortical organization
with the increased spatial and temporal resolution afforded by fMRI. fMRI
will be especially suitable for studying the tonotopic organization of
the auditory cortices, to delineate the presence of distinct tonotopically
organized regions, and to explore possible hemispheric differences in
tonotopicity.
