gms | German Medical Science

Artificial Vision 2015

The International Symposium on Visual Prosthetics

27.11. - 28.11.2015, Aachen

Spatial extent of neural responses evaluated by single-unit activities of the lateral geniculate nucleus elicited by suprachoroidal electrical stimulation

Meeting Abstract

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  • Hiroyuki Kanda - Dept. of Applied Visual Science, Osaka University, Osaka, Japan
  • T. Miyoshi - Dept. Of Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan
  • T. Morimoto - Dept. of Applied Visual Science, Osaka University, Osaka, Japan
  • T. Fujikado - Dept. of Applied Visual Science, Osaka University, Osaka, Japan

Artificial Vision 2015. Aachen, 27.-28.11.2015. Düsseldorf: German Medical Science GMS Publishing House; 2016. Doc15artvis20

doi: 10.3205/15artvis20, urn:nbn:de:0183-15artvis204

Veröffentlicht: 7. März 2016

© 2016 Kanda et al.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). Lizenz-Angaben siehe http://creativecommons.org/licenses/by/4.0/.


Gliederung

Text

Background: To estimate the spatial resolution of retinal prosthesis by suprachoroidal electrical stimulation, we recorded single-unit responses of the relay cells in the lateral geniculate nucleus (LGN).

Methods: Under general anesthesia, a recording electrode was inserted into the LGN of cats (n = 16), and single-unit activities were recorded. Receptive fields of the recorded cells were identified by light stimulation. For suprachoroidal stimulation, we used the two types of electrodes: a single platinum-based electrode (diameter = 0.1 mm) and multiple electrodes comprising bullet-shaped platinum electrodes (diameter = 0.5 mm and height = 0.3 mm each) (Terasawa et al, ARVO 2011). The stimulating electrodes were attached to the fenestrated sclera. Single biphasic pulses with 0.5 ms/phase were applied to the retina. And spike discharges evoked by suprachoroidal stimulation of various current intensities were recorded in each unit. The spatial extent of neural responses was evaluated by response probability in relation to the distance between the stimulation electrode and the center of the receptive field.

Results: Repetitive bursts were obtained in response to suprachoroidal stimulation. We focused on the early burst and measured the response probability. The relationship between the response probability and distance from the center of receptive fields showed that the size of distribution was decreased with a decrease in stimulation intensity. The minimum size of distribution was 1.8 degree in cat’s visual field evaluated from the half maximum value of half width.

Conclusions: If phosphene and the extent of the neural responses are similar in size, the spatial resolution of suprachoroidal stimulation can be 3.6 degrees. Spatial resolution by suprachoroidal approach could be acceptable for advanced RP patients, although the distance between the electrode and the retina in this approach is larger than that in epi- or sub-retinal approach.