A new neurophysiological method for studying signal processing in the hearing or auditory system has been developed for recording the electrical responses of the auditory nerve when sounds are presented. This electrical response is called the "peristimulus compound action potential", or PCAP. The PCAP is being used to investigate the neural basis of the phenomenon known as "forward masking". Forward masking is the reduction in the ability to hear one sound as the result of an immediately preceding sound. Forward masking plays an important role in speech communication and is also used in a large number of procedures that assess hearing performance. The results of these studies will contribute to a better understanding of the function of the auditory portion of the nervous system. In addition, because some of these electrical responses can be recorded in a noninvasive way from the ear canal of humans, it will be possible to expand these studies from laboratory animals to humans.
