Spatial properties of suprachoroidal-transretinal electrical stimulation for artificial retinas: an electrophysiological study of lateral geniculate neurons in cats

Abstract

Suprachoroidal-transretinal stimulation (STS), which we have developed as a less invasive electrical stimulating method for an artificial retina, was reported to elicit well localized field responses in the superior colliculus of retinal dystrophic rats (Kanda et al., 2004). In this study, we analyzed the spatial properties of STS evoked single-unit activities, which were recorded from the relay cells of the lateral geniculate nucleus (LGN) in anesthetized cats. A stimulating platinum electrode (diameter: 100 μm) was placed on the sclera with local lamellar resection, and a platinum wire (diameter: 0.2 mm) was inserted into the vitreous as the reference electrode. We obtained sixty-three single-unit responses of LGN relay cells to a biphasic pulse (duration: 0.5 ms) of STS. The latencies of their initial responses were ranged from 5-15 ms. The response probability of each unit depended on both stimulus intensities and the distance (D) between the retinal position of the receptive field and the stimulating electrode. With 200 μA of stimulus intensity, the response probabilities of the units were over 80% in the case of D less than one degree in visual angle, decreasing drastically to 10% more than three degrees. Thus, it is suggested that STS can stimulate the retina focally and be suitable for artificial retinas. [Jpn J Physiol 55 Suppl:S169 (2005)]