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Directional asymmetry in vertical smooth-pursuit and cancellation of the vertical vestibulo-ocular reflex in juvenile monkeys
| Title: | Directional asymmetry in vertical smooth-pursuit and cancellation of the vertical vestibulo-ocular reflex in juvenile monkeys |
| Authors: | Akao, Teppei Browse this author | | Kumakura, Yousuke Browse this author | | Kurkin, Sergei Browse this author →KAKEN DB | | Fukushima, Junko Browse this author →KAKEN DB | | Fukushima, Kikuro Browse this author →KAKEN DB |
| Keywords: | Smooth-pursuit | | Vestibular system | | VOR cancellation | | Gain | | Directional asymmetry | | Training | | Juvenile macaque | | Cerebellar flocculus |
| Issue Date: | Oct-2007 |
| Publisher: | Springer Berlin / Heidelberg |
| Journal Title: | Experimental Brain Research |
| Volume: | 182 |
| Issue: | 4 |
| Start Page: | 469 |
| End Page: | 478 |
| Publisher DOI: | 10.1007/s00221-007-1005-1 |
| PMID: | 17611746 |
| Abstract: | 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 |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/30145 |
| Appears in Collections: | 医学院・医学研究院 (Graduate School of Medicine / Faculty of Medicine) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 福島 菊郎
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