FENS Forum 2002

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First author: Greve, Nina (poster)
Session# 083 - Visual cortex and pathways III

Abstract# 083.7
Poster p249 - Mon 15/07, 12:00 - Corridor & Foyer Paris - Foyer Neuilly

Author(s) Greve N. (1), Schanze T. (1), Eger M. (1), Eckhorn R. (1), Wilms M. (1) & Hesse L. (2)
Addresse(s) (1) NeuroPhysics Grp., Philipps-University Marburg, Germany; (2) Dept. Ophthalmology, Philipps-University Marburg, Germany
Title Transmitting form and motion from retina implants to the visual cortex of cats.
Text Focal electrical stimulation of the retina can evoke localized phosphenes in blinds with photoreceptor degeneration [1] so that residual vision may become possible. Our present goal is to explore the possibilities and achievable resolutions for form and movement information by retina implants in intact anaesthetized cats. We tested the success of generating electrically form and movement representations in primary visual cortex (V1) by recordings of neural response profiles in V1. In our recent work in, we obtained estimates of spatial and temporal resolutions for a focal electrical stimulus (about 1 and 20 ms, respectively [2]). In the present study fibre electrodes were inserted through a small scleral incision onto the retinal surface for stimulation. In addition, we tested foil electrode arrays implanted epiretinally or subretinally between bipolar cells and pigment epithelium near the central retinal area. Retinal and cortical electrodes had corresponding visual locations, i. e., their visual receptive fields largely overlapped. Electrical stimuli were charge balanced impulses (50 to 1000 s; 1 to 500 A). Different basic form stimuli were constructed by positioning the tips of retinal electrodes systematically at different distances and angles and activating them synchronously. Basic movement stimuli were generated by translating the form stimuli to a second retinal position at various distances and delays, mimicking different velocities. We recorded spike activities and local field potentials (LFP) by an array of microelectrodes in V1. From the spatio-temporal activation profiles we estimated the relations between stimulation distance and angular resolution (form) and between spatial resolution and velocity (movement).
[1] MS Humayun et al (1996) Arch Ophthalmol 114: 40-46, [2] Schanze et al (2001) submitted.
(Support by BMBF grant 01 KP 0006 to RE, LH, and TS is greatly acknowledged).
Theme Sensory systems
Vision / Striat visual cortex: Neural coding and synchrony

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