Dynamic circuitry for updating spatial representations. I. Behavioral evidence for interhemispheric transfer in the split-brain macaque
Dynamic circuitry for updating spatial representations. I. Behavioral evidence for interhemispheric transfer in the split-brain macaque
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DOI：
10.1152/jn.00028.2005
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发表时间：
2005-11-01
影响因子：
2.5
通讯作者：
Colby, CL
中科院分区：
文献类型：
--
作者：
Berman, RA;Heiser, LM;Colby, CL
感官世界的内部表征必须不断调整，以考虑运动。在视觉系统中，空间更新提供了一种机制，用于在眼睛移动时维持显著位置的连贯地图。然而，人们对产生更新的空间表征的途径知之甚少。在本研究中，我们问是否需要直接的皮质-皮质链接的空间更新。我们通过调查前脑连合（两个皮质半球之间的直接路径）是否是从一个半野到另一个半野更新视觉表征所必需的来解决这个问题。我们评估了空间更新在两个裂脑猴使用双步骤的任务，其中包括扫视两个顺序出现的目标。准确的表现要求更新第二目标的表示以考虑第一扫视。关于空间更新的基础途径，我们有两个重要发现。首先，我们发现裂脑猴在双步骤序列上表现出选择性的初始损伤，这需要在视觉半野上进行更新。第二，也是最令人惊讶的是，这些损伤既不是普遍的，也不是永久性的：猴子最终能够执行跨半场序列，在某些情况下，这种能力迅速出现。这些研究结果表明，直接皮层链接提供了更新视觉表征的主要基板，但他们不是唯一的基板。相反，视觉空间的统一和稳定的表示是由冗余的皮质-皮质下网络支持的，该网络具有惊人的重组能力。
Internal representations of the sensory world must be constantly adjusted to take movements into account. In the visual system, spatial updating provides a mechanism for maintaining a coherent map of salient locations as the eyes move. Little is known, however, about the pathways that produce updated spatial representations. In the present study, we asked whether direct cortico-cortical links are required for spatial updating. We addressed this question by investigating whether the forebrain commissures - the direct path between the two cortical hemispheres - are necessary for updating visual representations from one hemifield to the other. We assessed spatial updating in two split-brain monkeys using the double-step task, which involves saccades to two sequentially appearing targets. Accurate performance requires that the representation of the second target be updated to take the first saccade into account. We made two central discoveries regarding the pathways that underlie spatial updating. First, we found that split-brain monkeys exhibited a selective initial impairment on double-step sequences that required updating across visual hemifields. Second, and most surprisingly, these impairments were neither universal nor permanent: the monkeys were ultimately able to perform the across-hemifield sequences and, in some cases, this ability emerged rapidly. These findings indicate that direct cortical links provide the main substrate for updating visual representations, but they are not the sole substrate. Rather, a unified and stable representation of visual space is supported by a redundant cortico-subcortical network with a striking capacity for reorganization.