Visualization of cat auditory cortical functional organization after electrical stimulation with a multichannel cochlear implant by means of optical imaging

Abstract

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.

Spatial Selectivity to Intracochlear Electrical Stimulation in the Inferior Colliculus is Degraded After Long-Term Deafness in Cats

“…In the present study, cochleotopic organization in the ICC was maintained even after very prolonged periods of deafness. This finding is in contrast to previous studies in the auditory cortex (Dinse et al 1997;Hartmann et al 1997;Klinke et al 1999;Schreiner 1999, 2003;Taniguchi et al 1997) suggesting that sustained lack of auditory input and severe degeneration of peripheral innervation result in a degradation of cortical cochleotopic organization. The present results suggest that the cochleotopicity of the ICC is less affected by long-term auditory deprivation than that of the auditory cortex.…”

Cochlear implants and brain plasticity

“…In contrast, neonatal deafening results not only in a similar spread of cortical activation as short-term deafness (i.e., a 6 dB supra-threshold stimulus activates a 3-to 4-mm wide dorso-lateral strip), but also in a complete or near-complete loss of the orderly mapping of cochlear location to cortical location (Fallon et al, 2007a;Raggio and Schreiner, 1999). Using optical imaging techniques, Dinse et al (2003Dinse et al ( , 1997a also reported a disintegration of the normal map, with the emergence of isolated islands or patches of activity in response to stimulation of a given electrode. The loss of cochleotopy in AI is in contrast to the electrophysiological evidence from lower centres, most notably the IC, in which a near-normal cochleotopic organisation is maintained even after extended periods of deafness (Leake et al, 2000;Moore et al, 2002;Shepherd et al, 1999;Snyder et al, 1990).…”

Plastic Changes in the Auditory Cortex of Congenitally Deaf Cats following Cochlear Implantation

“…In early implanted experienced CDCs, however, the auditory cortex displayed activity, indicating that it was functional in these CDCs. Cortical activation with intracochlear electrical stimulation has also been demonstrated using techniques of optical imaging [Dinse et al, 1997]. Scheich [1996, 1997] demonstrated learning effects in gerbil auditory cortex.…”