[Effects of fornix lesion on visual evoked responses during sleep and wakefulness in rats]

The effects of fornix lesion on visual evoked responses (VERs) recorded from the occipital cortex (OCX) and the lateral geniculate body (LGB) were examined during wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS) respectively, in freely moving rats (N = 6). In intact animals, amplitudes of VERs changed with sleep-waking stages in a decreasing order of SWS, PS and W. After fornical lesion, mean amplitudes of VERs were significantly enhanced at OCX, but not at LGB. As to OCX, amplitudes of early components of VERs increased during all sleep-waking stages, and those of later components increased only during sleep. These results suggest that the fornix system exerts some modulatory (probably inhibitory) influence on OCX in close relations to sleep-waking stages in rats.