Purchase this article with an account.
UT Eysel, P Walter, F Gekeler H Schwahn E Zrenner, HG Sachs V-P Gabel, ZF Kisvárday; Optical Imaging Reveals 2-Dimensional Patterns of Cortical Activation After Local Retinal Stimulation With Sub- and Epiretinal Visual Prostheses . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4486.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Localized retinal stimulation with miniaturized visual prostheses should be suited to generate spatio-temporal patterns of cortical activation. To conservatively judge the possible resolution, 2-dimensional patterns of cortical activation after focal retinal stimulation with epi- and subretinal implants were obtained by optical imaging of intrinsic signals. Methods: Small microelectrode array chips were acutely implanted sub- or epiretinally into the eyes of adult cats. After surgery single electrodes were electrically stimulated (biphasic, 0.25 ms, 2-100 µA), electric field potentials were recorded in the optic tract to ensure the micro-array function and optical imaging of intrinsic signals in the visual cortex was performed with the Imager 2001 (Optical Imaging, USA). Results: Optic tract field potentials were elicited from all electrodes in the epi- and subretinal electrode arrays with currents between 4 and 78 µA. The 2dimensional patterns of cortical activation revealed a precise cortical retinotopy when repetitively evoked from electrodes spaced by 750µm (epiretinal) or 330µm (subretinal). The peaks of intrinsic activity were well separated and showed a spatial spread of 1.8 mm at half height both for the epi- and the subretinal implants. This is equivalent to a visual resolution of 1.25° at 2° retinal eccentricity. Conclusion: Focal stimulation of the retina with subretinally or epiretinally implanted microelectrode arrays that have been developed in the German retina implant project evokes retinotopically organized activity in the visual cortex. The obtained point spread functions represent the worst possible estimate of spatial resolution, since intrinsic signals visualize supra- and sub-threshold and excitatory as well as inhibitory activity without differentiation. On the basis of this conservative estimate of spatial resolution one can assume that human subjects supplied with this kind of visual prostheses would gain visual information that could considerably improve practical capabilities in everyday life.
This PDF is available to Subscribers Only