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Directional asymmetry in vertical smooth-pursuit and cancellation of the vertical vestibulo-ocular reflex in juvenile monkeys

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タイトル: Directional asymmetry in vertical smooth-pursuit and cancellation of the vertical vestibulo-ocular reflex in juvenile monkeys
著者: Akao, Teppei 著作を一覧する
Kumakura, Yousuke 著作を一覧する
Kurkin, Sergei 著作を一覧する
Fukushima, Junko 著作を一覧する
Fukushima, Kikuro 著作を一覧する
キーワード: Smooth-pursuit
Vestibular system
VOR cancellation
Gain
Directional asymmetry
Training
Juvenile macaque
Cerebellar flocculus
発行日: 2007年10月
出版者: Springer Berlin / Heidelberg
誌名: Experimental Brain Research
巻: 182
号: 4
開始ページ: 469
終了ページ: 478
出版社 DOI: 10.1007/s00221-007-1005-1
抄録: Young primates exhibit asymmetric eye movements during vertical smooth-pursuit across a textured background such that upward pursuit has low velocity and requires many catch-up saccades. The asymmetric eye movements cannot be explained by the un-suppressed optokinetic reflex resulting from background visual motion across the retina during pursuit, suggesting that the asymmetry reflects most probably, a low gain in upward eye commands (Kasahara et al. in Exp Brain Res 171:306–321, 2006). In this study, we examined (1) whether there are intrinsic differences in the upward and downward pursuit capabilities and (2) how the difficulty in upward pursuit is correlated with the ability of vertical VOR cancellation. Three juvenile macaques that had initially been trained only for horizontal (but not vertical) pursuit were trained for sinusoidal pursuit in the absence of a textured background. In 2 of the 3 macaques, there was a clear asymmetry between upward and downward pursuit gains and in the time course of initial gain increase. In the third macaque, downward pursuit gain was also low. It did not show consistent asymmetry during the initial 2 weeks of training. However, it also exhibited a significant asymmetry after 4 months of training, similar to the other two monkeys. After 6 months of training, these two monkeys (but not the third) still exhibited asymmetry. As target frequency increased in these two monkeys, mean upward eye velocity saturated at ∼15°/s, whereas horizontal and downward eye velocity increased up to ∼40°/s. During cancellation of the VOR induced by upward whole body rotation, downward eye velocity of the residual VOR increased as the stimulus frequency increased. Gain of the residual VOR during upward rotation was significantly higher than that during horizontal and downward rotation. The time course of residual VOR induced by vertical whole body step-rotation during VOR cancellation was predicted by addition of eye velocity during pursuit and VOR x1. These results support our view that the directional asymmetry reflects the difference in the organization of the cerebellar floccular region for upward and downward directions and the preeminent role of pursuit in VOR cancellation.
Rights: The original publication is available at www.springerlink.com
資料タイプ: article (author version)
URI: http://hdl.handle.net/2115/30145
出現コレクション:雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

提供者: 福島 菊郎

 

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