ネコ水平眼運動系におけるａｓｃｅｎｄｉｎｇ ｔｒａｃｔ ｏｆ Ｄｅｉｔｅｒｓ’の関与について

Abstract

There are two distinct excitatory projections to the medial rectus (MR) motoneuron pool from the posterior brain stem in the cat. First, abducens internuclear neurons send their axons into the contralateral medial longitudinal fasciculus to terminate upon MR motoneurons. Secondly, the ascending tract of Deiters' (ATD) also terminates upon MR motoneurons.We studied the effects of a unilateral ATD lesion on the horizontal eye movements evoked by optokinetic and vestivular stimuli. ENGs were recorded prior to and after the lesion was induced in the fully alert cat. The eye velocity on the side of the lesion during the slow and fast phases was compared with that of the intact side. The lesion to the ATD was confirmed histologically and physiologically.The lesion of the right ATD resulted in the following: (1) During clockwise OKN stimulation (optokinetic rotation to the right), the slow phase eye velocity on the side of the lesion was slower than that of the intact side, while the fast phase eye velocity was not affected. (2) During counterclockwise stimulation, neither the slow nor fast phase eye velocity of either side was affected. (3) During caloric stimulation, slow and fast phase eye velocity was not changed. On the basis of these data, we concluded that ATD was one of the final pathways mediating the visual signals responsible for OKN.