The objectives of this project are to study: (1) the effects of acquired- and congenital-hearing loss on central auditory structures; (2) the chemistry of cochlear transduction; and (3) central auditory phenomena in normal subjects, subjects with auditory-processing disorders, and subjects with documented focal, cortical lesions. The studies on the effects of hearing loss on central structures are focused on documenting changes in the spiral ganglion, cochlear nucleus, and olivary complex. The studies of cochlear chemistry deal specifically with identification of the afferent nerve transmitter substances in mammals and other vertebrates. The studies of central auditory phenomena in humans are designed to elucidate structure-function relationships for processing complex acoustic signals (such as speech), and to gain a better understanding of the functional deficits associated with learning disabilities classed as "auditory-processing disorders".