The electroretinogram and visual evoked potential of freely moving rats

The vascularised rat retina could be one of the most useful experimental ob jects in visual neuroscience to understand human visual physiological and p athological processes. We report here on a new method of implantation for s tudying the visual system of freely moving rats that provides a rat model f or simultaneous recording at corneal and cortical level and is stable enoug h to record for months. We implanted light emitting diodes onto the skull b ehind the eyeball to stimulate the eye with flashes and to light adapt the retina with constant light levels. A multistrand, stainless steel, flexible fine wire electrode placed on the eyeball was used for electroretinogram r ecording and screw electrodes (left/right visual and parietal cortical) wer e used to record the visual evoked potential and the electroencephalogram. In the present report we focus on the new method of implantation for record ing the corneal flash electroretinogram of normal, freely moving rats simul taneously with the visual evoked cortical potential showing examples in var ious visual experiments. We also introduce a program for retinogram and vis ual evoked potential analysis, which defines various measures (latencies, a reas, amplitudes, and durations) and draw attention to the benefits of this method for those involved in visual, functional genomic, pharmacological, and human ophthalmologic research. (C) 2001 Elsevier Science Inc.