The long-term goal of this research program is a comprehensive description of human auditory cortex organization. What are its structural components and what are their functions? How do these elements work together to produce the perceptual experience of hearing? Underlying current conceptions is a regional (modular) system of organization formed by an interconnected group of cortical areas, but the number of areas involved and their connections are unknown for humans. A testable working model of human auditory cortex has not been developed, even though such models are fundamental to studies of auditory cortex in other species. To establish this model, detailed neuroanatomical analyses will be used to reveal the underlying structures that comprise this part of the brain. Efforts will focus on the planum temporale in the superior temporal lobe, which is thought to be an important region for integrating the neural codes required to perceive and interpret sound. Although often treated as a single area, the planum temporale appears to contain several areas that are anatomically and physiologically distinct. Temporal lobes will be obtained postmortem and processed for marker proteins of neurons, axons, neurofilaments, and key enzymes. Areas will be profiled and compared on the basis several measurements (surface area, cortical thickness, neuron density, optical density). The research will be guided and grounded by comparative studies of other primates, which continue to provide an invaluable foundation for studies of auditory cortex in humans. In addition, parallel studies in monkeys will focus on the connections and neuron response properties in the posterior temporal lobe that correspond to the human planum temporale. The relevance of this research applies broadly to patient populations in which the temporal lobe is involved, and directly supports related areas of research involving both normal and clinical populations. These include: 1) Noninvasive methods to study auditory activity in the human brain (e.g., functional imaging);2) Neurosurgical planning and assessment of function associated with surgery, injury, or related pathology (e.g., cerebrovascular accidents, tumors);3) Evaluation of cortical function in clinical populations in which auditory processing or memory is affected (e.g., Alzheimer's, schizophrenia, autism, dyslexia, epilepsy, language delay, hearing impairment, and aging);and 4) Maturational and genomic studies of auditory cortex in normal and clinical populations.
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