Speech sounds are the most important sounds that we hear;yet little is known about how these stimuli are represented by neural activity within human auditory cortex. The goal of our research is to understand the functional organization and connections of those areas of human cerebral cortex that are engaged in sound processing and examine how auditory speech stimuli are represented in these regions. These experiments involve combining anatomical and functional MRI methods with direct cortical electrophysiological recordings and electrical stimulation techniques in awake, behaving human subjects undergoing clinical evaluation of intractable epilepsy. We will pursue our goals by testing a series of specific hypotheses regarding: (1) the locations and functional properties of auditory cortical fields;(2) the manner in which evoked responses to speech stimuli are represented and transformed within these fields;and (3) the functional connections and patterns of information flow between these fields. These objectives are pursued by an experienced multidisciplinary team using combinations of non-invasive MRI and direct investigative methods in order to gather complementary sets of human physiological and anatomical data in the same experimental subjects. These data cannot be obtained using non-invasive methods alone, and this multi-modal experimental approach is designed to overcome significant barriers that currently impede research progress in this field. To our knowledge, if our objectives are achieved, the resulting data will be the first of its kind demonstrating directly how acoustic and phonetic speech information is represented by neural activity within multiple physiologically-defined auditory fields of the superior temporal plane and lateral superior temporal gyrus as subjects engage in psychophysical speech-processing tasks. We pursue these research objectives believing that knowledge of the fundamental structure and function of the normal human auditory system is essential to understanding mechanism that underlie impairment of all aspects of hearing, speech, and language.
This research program generates unique information about the functional organization of human auditory cortex that cannot be obtained using alternative, non-invasive approaches. Knowledge gained from these studies will provide new insights into how speech information is represented within the human brain and aid in the rational design of new therapeutic and rehabilitation strategies for patients affected by a wide range of communication disorders.
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