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.

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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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