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Activation zones in cat visual cortex evoked by electrical retina stimulation

  • Thomas Schanze
  • Marcus Wilms
  • Marcus Eger
  • Lutz Hesse
  • Reinhard Eckhorn
Laboratory Investigation

Abstract

Background. A retina implant for restoring simple basic visual perception in patients who are blind due to photoreceptor loss requires optimisation of stimulation parameters for obtaining high spatio-temporal resolution. We developed effective low-power epi-retinal stimulation and intracortical recording in semichronically prepared cats.

Methods. Individually driveable fibre electrodes were inserted through a small scleral incision and positioned at the area centralis. Polyimide–platinum film electrodes were inserted via a corneal incision and fixed by instillation of perfluorocarbon liquid on the internal limiting membrane. For electrical stimulation we used short charge-balanced current impulses of 100–400 µs duration and amplitudes ranging from 1 to 100 µA. During stimulation we recorded multiple single-cell and population activities from areas 17 and 18. Recordings were stored digitally. Stimulus–response relations including response strength, cortical activation zones, information transmission, and electrical receptive fields were analysed off-line.

Results. We found low-threshold activations with fibre electrodes and polyimide–platinum film electrodes in close mechanical contact to the retina. Retinal stimulation with bipolar charge-balanced impulses resulted in cortical activation zones corresponding to 1–5° visual angle at paracentral locations dependent on the eccentricity of the retinal stimulation point. Retino-cortical transinformation analysis revealed 20–30 bits/s per electrode, corresponding to 10–15 four-level pictures/s. Electrical receptive fields had sizes of 1–3° visual angle.

Conclusions. Coarse visuomotor coordination and navigation seems possible with retina implants.

Keywords

Retina Polyimide Visual Angle Perfluorocarbon Corneal Incision 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Thomas Schanze
    • 1
  • Marcus Wilms
    • 1
  • Marcus Eger
    • 1
  • Lutz Hesse
    • 2
  • Reinhard Eckhorn
    • 1
  1. 1.Applied Physics–NeuroPhysics Group, Department of Physics, Philipps University Marburg, Renthof 7, 35032 Marburg, Germany
  2. 2.Department of Ophthalmology, Philipps University Marburg, Robert-Koch-Straße 4, 35037 Marburg, Germany

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