The congenital absence of corpus callosum has been recently found to occur among some mice of the ddN strain in our laboratory. In this experiment, the differences of the visual evoked potentials among the normal corpus callosum, callosal hypogenesis and agenesis in ddN strain mice were investigated. One-Hz- flash stimulations were given on the left eye through a glass fiber connector from the EEG stimulator. Under Nembutal anesthesia, two hundred times of average evoked field potentials were recorded from the contralateral and ipsilateral visual cortices. Electrophysiologically, the normal mice showed complete decussation on the opic chiasm. On the other hand, the complete acallosal mice could be classified into two types, such as those of complete decussation and those of absence of optic chiasm. In the complete decussation of acallosal mice, the latency, peak latency and duration of these potentials from ipsilateral side significantly prolonged, and the amplitude of the potentials extremely diminished. In the absence of optic chiasm of complete acallosal mice, the potentials were obtained only in ipsilateral cortex. After amputation of the corpus callosum in the normal mice, the visual evoked field potential showed similar to acallosal mice. However, in the hypogenesis of corpus callosum, there was no significant difference in the potentials compared with the normal mice.
Visual evoked field potential