Positron emission tomographic study of auditory sensation in a patient with a cochlear implant.

The speech comprehension ability of patients with a cochlear implant is fairly good even when information from the implant device is insufficient. It is presumed that the higher brain system has important roles in discriminating speech. The purpose of the present study was to investigate the function of the auditory cortices of a patient with a cochlear implant before and after sound signal inputs. In this study, we used positron emission computed tomography, which can detect brain activity by providing quantitative measurements of the metabolic rates of oxygen and glucose. Without sound signals, the auditory cortices of the patient showed remarkably low metabolic rates. However, with the cochlear implant device, the activity returned to near normal levels. These findings suggest that the activation of the speech comprehension mechanism of the higher brain system can be initiated by sound signals from the implant device.