Visually Evoked Cortical Potentials Obtained Using Checker Patterns in Albino Rats

Abstract

Visually evoked cortical potentials (VECPs) were recorded in fifteen albino rats, which were typically used in toxicology studies, using a checkerboard with various stimulation patterns including various checker sizes, various stimulation frequencies and various stimulation luminances. The electrodes for recording the VECPs were implanted chronically on the surface of the visual cortex. Rats were anesthetized lightly with a mixture of xylazine and ketamine, and placed in front of a pattern-generating TV monitor which displayed checks becoming white and black. Reproducible waveforms with an initial positive wave (P1) followed by a large negative wave (N1) were recorded with checker sizes larger than 50mm. Steady-state responses were recorded with stimulation frequencies higher than 4Hz. No changes were found with variation in stimulus luminance. The P1 latencies were reproducible among animals and records. These results indicate that this technique for VECPs can be used to detect changes in visual function in albino rats.