Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Anatomy and Cell Biology


Stephen G Lomber


Sensory localization within cortex is a widely accepted and documented principle. Within cortices dedicated to specific sensory information there is further organization. For example, in visual cortices a more detailed functional division and hierarchical organization has been recorded in detail. This organization starts with areas dedicated to analysis of simple visual stimuli. Areas higher in the organization are specialized for processing of progressively more complex stimuli. A similar hierarchical organization has been proposed within auditory cortex and a wealth of evidence supports this hypothesis. In the cat, the initial processing of simple auditory stimuli, such as pure tones, has been well documented in primary auditory cortex (A1) which is also the recipient of the largest projection from the thalamus. This indicates that at least the initial stages of a hierarchy exist within auditory cortex. Until now it has been difficult to investigate the remaining hierarchy in its entirety because of methodological limitations. In the present set of investigations the use of functional magnetic resonance imaging (fMRI) facilitated the investigation of auditory cortex of the cat in its entirety. Results from these investigations support the proposed hierarchy in auditory cortex in the cat with lower cortical areas selectively responding to more simple stimuli while higher areas are progressively more responsive to complex stimuli.