Ipsilateral sensitivity to visual motion is restricted to V5/MT+ in the right cerebral hemisphere
Ipsilateral sensitivity to visual motion is restricted to V5/MT+ in the right cerebral hemisphere
复制标题
同侧对视觉运动的敏感性仅限于右大脑半球的 V5/MT
DOI：
10.1167/17.10.607
复制
发表时间：
2017
影响因子：
1.8
通讯作者：
Strong S
中科院分区：
文献类型：
--
作者：
Strong S
以往的实验已经证明，经颅磁刺激(TMS)人右侧大脑半球的V5/MT+可导致对侧和同侧视觉半球的视觉运动知觉障碍。然而，当TMS被应用于左半球的V5/MT+时，运动障碍仅限于对侧半视野(Thakral和Slotnick，2011)。对这一结果的解释可能在于对V5/MT+内两个半球的亚区的不同刺激。V5/MT+有两个主要的细分：MT/TO-1和MST/TO-2。MST/TO-2含有大感受野(RF)神经元，可延伸到同侧半脑野。MT/TO-1神经元的RFs较小，不会明显延伸到同侧视野。我们想要重新检查左右半球V5/MT+之间的这种功能不对称性，并确定运动缺陷的模式是否依赖于MT/TO-1或MST/TO-2被TMS破坏的程度。使用引导TMS靶点的fMRI定位器，在6名受试者中识别MT/TO-1和MST/TO-2。当TMS脉冲与刺激开始同步施加时，受试者识别出现在左侧或右侧视野中的一致移动的点的阈值水平的平移方向(向上/向下)。对右侧MT/TO-1和MST/TO-2应用TMS后，对侧和同侧视野的方向辨别能力均受到干扰，而对左侧MT/TO-1和MST/TO-2应用TMS后的方向辨别能力仅限于对侧视野。这一结果表明，右脑在处理全场平移运动中的作用增强，但与我们的假设相反，影响在两个半球之间不同，而不是在V5/MT+的细分区域内。这与研究左半球和右半球时序差异的文献相一致(Ffytche等人，2000年)，然而这种不对称的原因仍然不清楚。
Previous experiments have demonstrated that transcranial magnetic stimulation (TMS) of human V5/MT+ in the right cerebral hemisphere can induce deficits in visual motion perception in both the contra-and ipsi-lateral visual hemi-fields. However, when TMS is applied to V5/MT+ in the left hemisphere, motion deficits are restricted to the contra-lateral hemi-field (Thakral and Slotnick, 2011). An explanation for this result might lie in differential stimulation of sub-divisions within V5/MT+ across the two hemispheres. V5/MT+ has two major sub-divisions; MT/TO-1 and MST/TO-2. MST/TO-2 contains neurons with large receptive fields (RFs) that extend up to 15 into the ipsi-lateral hemi-field. RFs of MT/TO-1 neurons are smaller and do not extend significantly into the ipsi-lateral field. We wanted to re-examine this functional asymmetry between V5/MT+ in the right and left hemispheres and ascertain whether the pattern of motion deficits is dependent upon the extent to which either MT/TO-1 or MST/TO-2 are disrupted by TMS. MT/TO-1 and MST/TO-2 were identified in six subjects using fMRI localisers that directed target points for TMS. Subjects identified the translational direction (up/down) of a threshold level of coherently moving dots presented in either the left or right visual field whilst TMS pulses were applied synchronously with stimulus onset. Application of TMS to MT/TO-1 and MST/TO-2 in the right hemisphere disrupted direction discrimination in both the contra-and ipsi-lateral visual fields, whereas deficits following application of TMS to MT/TO-1 and MST/TO-2 in the left hemisphere were restricted to the contra-lateral visual field. This result suggests an enhanced role for the right hemisphere in processing full-field translational motion, but contrary to our hypothesis, effects differ across hemispheres rather than within sub-divisions of V5/MT+. This corresponds to literature investigating timing differences across the left and right hemispheres (Ffytche et al., 2000), however the reasons for this asymmetry are still unclear.