[Changes of torsional eye movements after lesion of the rostral interstitial nucleus of the MLF (riMLF)--analysis on listing's plane].

The changes of torsional eye movements after the riMLF (rostral interstitial nucleus of the medial longitudinal fasciculus) lesions with kainic acid have been investigated in three rhesus monkeys. After unilateral lesion, torsional rapid eye movements were lost to ipsi-torsional (extorsion of the ipsilateral eye and intorsion of the contralateral eye) side only, while vertical movements were still possible. All monkeys showed counter-torsional (intorsion of the ipsilateral eye and extorsion of the contralateral eye) shifts and thickening of Listing's plane. These changes of Listing's plane were always less in the dark. After the second contralateral lesions, all torsional and vertical rapid eye movements were permanently lost. Listing's plane moved to the opposite torsional direction beyond zero. On-average, the residual torsional shift in the light was only 17.4% of the shift in the light after the first lesion. Furthermore, the thickness of Listing's plane decreased to the level of the pre-lesion state. These results suggest that burst neurons in the riMLF are essential to generate vertical and/or torsional rapid eye movements and symmetrical activity of them is necessary to keep Listing's plane around zero and to minimize its variability. Yet, after bilateral lesions, Listing's law is still preserved, suggesting its neural implementation in parallel to or downstream of the riMLF.