Evoked cortical potentials after electrical surface stimulation of the rabbit's retina

Purpose. To demonstrate successful electrical stimulation of the retina in rabbits and to separate artificial responses due to passive signal conduction from event related cortical activity. Methods: Pigmented rabbits were vitrectomized after previous injection of tissue plasminogen activator. An array of stimulating electrodes was implanted onto the retinal surface and temporarily fixated under PFCL. Stimulation was performed with bi- or monophasic resp. bi- or monopolar single pulses or pulse trains with stimulus currents of 10-200 mu A and a duration of 100 mu s. Evoked potentials could be recorded using gold plated electrodes after trepanation of the skull over the visual cortex and a reference electrode at the forehead. Results. Event related cortical potentials could be recorded after biphasic cathodic pulse train stimulation using 30 µA or more. The EEP amplitude increased with stimulus intensity. EEP threshold increased using single pulse stimulation.