gms | German Medical Science

Objective: To evaluate the spatial and temporal resolution obtained upon electrical sinusoidal stimulation of retinal circuits in photoreceptor-degenerated mouse retina.

Materials and methods: We interfaced ex vivo retina from photoreceptor-degenerated retina in epiretinal configuration to CMOS-based MEAs comprising 1024 stimulation electrodes (spatial resolution: 32 µm). Interleaved to the stimulation electrodes is an array of recording electrodes (4225 sensors, 16 µm spacing), which allows to simultaneously record the spiking activity of retinal ganglion cells. Sinusoidal waveforms (40 Hz) were applied in epiretinal configuration to a subset of electrodes. The stimulated ganglion cell spiking activity was evaluated by using classifier (regularized logistic regression) to decode stimulus identity.

Results: Robust modulation of the spiking activity was obtained for stimulation frequencies up to 40 Hz. The spatial selectivity was tested by stimulating two shapes separated by 32 µm only. Distinct spiking patterns and the high-accuracy performance of the decoder indicate that small spatial displacements of about 1 deg can be discriminated with high accuracy.

Discussion: Here we present the first evidence that the smallest spatially separable electrically stimulated shapes correspond to 1 deg visual angle on the mouse retina, which is the highest reported value for ex vivo blind retina. In ongoing experiments, we evaluate the spatial and temporal resolution obtained in subretinal configuration.

Acknowledgment: This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Projektnummer 276693517 – SFB 1233 and partially by a BMBF grant to GZ