The speech comprehension ability of cochlear implant patients is fairly good in spite of the fact that insufficient information is being received from the cochlear implant device. It is presumed that the higher central nervous system has an important role in discriminating speech. The purpose of the present study was to investigate the function of the primary and associate auditory cortex of a cochlear implant patient before and after sound signal inputs from the cochlear implant device. In this study we used positron emission computed tomography (PET), which can detect brain activity by providing quantitative measurements of the regional cerebral blood flow and the metabolic rates of oxygen and glucose. Without sound signals the primary auditory cortex and associate cortex of cochlear the implant patient showed remarkably low metabolic rates. However, when the cochlear implant device was used, the activities of both cortices returned to near normal levels. These findings suggest that activation of the speech comprehension mechanism of the higher central nervous system can be initiated by simple sound signals from the cochlear implant device.
