Visualization of Cat Auditory Cortical Functional Organization after Electrical Stimulation with a Multi-Channel Cochlear Implant by Means of Optical Imaging

In order to study the effects of acute electrical cochlear stimulation on the topography of the cat auditory cortex, we measured reflectance changes by means of optical imaging of intrinsic signals. Following single pulse electrical stimulation at selected sites of a multichannel implant device, we found topographically restricted response areas. Systematic variation of the stimulation pairs and thus of the cochlear frequency sites revealed a systematic and corresponding shift of the response areas. Increasingly higher stimulation currents evoked increasingly larger response areas resulting in decreasing spatial, i.e. cochleotopic selectivity. The results indicate that optical imaging intrinsic signals is useful to visualize effects of cochlear stimulation, which results in a profound cochleotopic selectivity. The implications of these findings are discussed in respect to underlying mechanisms of sound sensation mediated by cochlear implants.