R. Zeitler, P. Fromherz, G. Zeck
Neuroprosthetic devices rely on a tight contact between electrodes and neurons in the interfaced tissue. A simple method to probe the contact properties in a non-invasive way would be highly attractive. Here we show for retinal tissue that crucial electrical properties of the interface can be extracted from the voltage noise that is recorded with an array of capacitive sensors. The monitoring of the interface properties, which are either interpreted as variable local conductivities or as a cleft of varying distance, allows assessment of the long-term efficiency of neuroprosthetic devices.
Figure 3. Estimated maps of the retina-chip interface. (a) Experimen¬tal PSD at low frequencies represented as a map of the effective resistance Reff (x,y) that is defined by the Nyquist relation. (b) Interpretation of the effective resistance in terms of a model of the retina-chip contact as a map of the tissue conductivity sigma tissue(x,y) > 0.8 mS/cm assuming a perfect contact with a distance dcleft =0, and as a map of the distance dcleft(x,y) > 0 assuming a constant tissue conductivity sigma tissue =0.8 mS/cm.
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