Attentional Modulation of Human Auditory Cortex

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DESCRIPTION (provided by applicant): Although human auditory cortex has traditionally been subdivided into auditory cortical fields based largely on anatomical analysis and the extrapolation of functional data from other primate species, much remains to be discovered about human auditory cortical organization. Extrapolating functional data from other species is problematic because the human specialization for speech processing may have significantly altered auditory cortical organization. We propose two groups of experiments using high-resolution functional magnetic resonance imaging (fMRI) and improved landmark-based mapping procedures to provide detailed functional maps of human auditory cortical fields. Since our preliminary results indicate that attention-related activations equal or exceed those produced by the stimuli themselves, attention will be controlled and manipulated in all experiments. Activations to nonattended stimuli will elucidate automatic sensory responses, whereas attention-related differences in activations will clarify the optional, higher-cognitive operations involved in audition. Experiments 1-3 will use simple stimuli to derive auditory field maps in humans similar to those obtained in macaques. Experiments 4-7 will use speech and speech-control stimuli to characterize speech-related activations. Repeated single-subject testing and improved imaging procedures will permit auditory cortical fields to be mapped with unprecedented detail during the processing of simple sounds, syllables and coherent speech.