SPATIOTEMPORAL SOURCE MODELING OF EVOKED-POTENTIALS TO ACOUSTIC AND COCHLEAR IMPLANT STIMULATION

Spatio-temporal source modeling (STSM) of event-related potentials was used to estimate the loci and characteristics of cortical activity ev oked by acoustic stimulation in normal hearing subjects and by electri cal stimulation in cochlear implant (CI) subjects. In both groups of s ubjects, source solutions obtained for the N-1/P-2 complex were locate d in the superior half of the temporal lobe in the head model. Results indicate that it may be possible to determine whether stimulation of different implant channels activates different regions of cochleotopic ally organized auditory cortex. Auditory system activation can be asse ssed further by examining the characteristics of the source wave forms . For example, subjects whose cochlear implants provided auditory sens ations and normal bearing subjects had similar source activity. In con trast, a subject in whom implant activation evoked eyelid movements ex hibited different source wave forms. STSM analysis may provide an elec trophysiological technique for guiding rehabilitation programs based o n the capabilities of the individual implant user and for disentanglin g the complex response patterns to electrical stimulation of the brain .