SACCADE-RELATED ACTIVITY IN THE LATERAL INTRAPARIETAL AREA .2. SPATIAL PROPERTIES
SACCADE-RELATED ACTIVITY IN THE LATERAL INTRAPARIETAL AREA .2. SPATIAL PROPERTIES
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DOI：
10.1152/jn.1991.66.3.1109
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发表时间：
1991-09-01
影响因子：
2.5
通讯作者：
ANDERSEN, RA
中科院分区：
文献类型：
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作者：
BARASH, S;BRACEWELL, RM;ANDERSEN, RA
1. 当猕猴执行延迟眼跳和相关任务时，记录其下顶叶小叶 (IPL) 的单神经元活动。配套论文中介绍了该活动的时间特征。这里我们重点关注活动的空间特征。该分析基于 145 个神经元的记录。所有这些神经元都来自外侧顶叶区 (LIP)，这是最近定义的 IPL.2 的一个细分。延迟扫视是在八个方向上进行的。在配套论文中描述的以下每个活动阶段，计算每个神经元的方向调谐曲线：光敏感（LS）、延迟期记忆（M）和眼跳相关（S）；后者进一步分为眼跳前(Pre-S)、眼跳重合(S-Co)和眼跳后(Post-S)。3．计算每条方向调整曲线的宽度和首选方向。我们研究了 LIP 神经元群的宽度和偏好方向的分布。在每种情况下，我们只包括在所讨论的阶段中表现出明显兴奋活动的神经元。4。宽度定义为响应高于其最大净值 50% 的角度。研究的所有相的宽度分布相似。神经元之间的宽度差异很大，从非常窄（< 45 度）到非常宽（接近 360 度）。所有相位的中位宽度约为 90 度。5。各个阶段的首选方向分布也相似。每个分布都代表了所有方向，但对侧方向更为常见（例如，S-Co 为 69%）。6。对于每个神经元，确定其各个阶段的首选方向的对齐。计算对齐的分布（再次，忽略不明显兴奋的阶段）。在神经元群体的水平上，LS、M 和 Pre-S 彼此非常一致。 S-Co 也与这些相一致，但不太精确。7。通过施加窄（宽度，< 90 度）LS 和 S-Co 方向调谐的约束来选择一组“窄调谐”神经元。在这组神经元中，LS 和 S-Co 的首选方向非常一致（中位，12 度）。群体中窄调神经元的比例为 40% (25/63)。因此，在 LIP 区域的大量亚群中，感觉场和运动场之间存在相当精确的对准。8。当猴子对位于小、中、大假想圆上的 32 个目标进行延迟扫视时，记录了另外一组 82 个区域 LIP 神经元。分别计算三个圆圈中每个神经元每个活动阶段的首选方向。同一相的优选方向在不同的圆上很好地对齐。这一观察结果支持了方向偏好的存在，而不是严格依赖于偏心率。我们还分别计算了每个圆不同阶段之间的对齐情况。对齐的分布是相似的，表明我们的结果不是所使用的偏心率的特殊性。9。 Post-S 活动与 Pre-S 阶段并不一致。 Post-S 活动与 Pre-S 阶段的对齐分布是平坦的。10。当猴子执行向后扫视和双扫视范式时，我们记录了 33 个神经元。即使在其感受野中没有发生视觉刺激，LIP 中的神经元也会在预期其运动场中出现眼跳时变得活跃，也就是说，这些神经元在运动坐标中进行编码。11。 LIP 区域活动的这些特征表明，该皮质区域参与了视觉信息的转换，以规划眼跳运动。
1. Single-neuron activity was recorded from the inferior parietal lobule (IPL) of Macaca mulatta monkeys while they were performing delayed saccades and related tasks. Temporal characteristics of this activity were presented in the companion paper. Here we focus on the spatial characteristics of the activity. The analysis was based on recordings from 145 neurons. All these neurons were from the lateral intraparietal area (LIP), a recently defined subdivision of the IPL.2. Delayed saccades were made in eight directions. Direction-tuning curves were calculated for each neuron, during each of the following activity phases that were described in the companion paper: light sensitive (LS), delay-period memory (M), and saccade related (S); the latter further partitioned into presaccadic (Pre-S), saccade coincident (S-Co), and postsaccadic (Post-S).3. Width and preferred direction were calculated for each direction-tuning curve. We studied the distributions of widths and preferred directions in LIP's neuronal population. In each case we included only neurons that showed clear excitatory activity in the phases in question.4. Width was defined as the angle over which the response was higher than 50% of its maximal net value. Width distributions were similar for all phases studied. Widths varied widely from neuron to neuron, from very narrow (< 45-degrees) to very wide (close to 360-degrees). Median widths were approximately 90-degrees in all phases.5. Preferred-direction distributions were also similar for various phases. All directions were represented in each distribution, but contralateral directions were more frequent (e.g., 69% for S-Co).6. For each neuron the alignment of the preferred directions of its various phases was determined. Distributions of alignments were calculated (again, phases that were not clearly excitatory were disregarded). On the level of the neuronal population LS, M, and Pre-S were well aligned with each other. S-Co was also aligned with these phases, but less precisely.7. A set of "narrowly tuned" neurons was selected by imposing a constraint of narrow (width, < 90-degrees) LS and S-Co direction tuning. In this set of neurons, the LS and S-Co preferred directions were very well aligned (median, 12-degrees). The fraction of narrowly tuned neurons in the population was 40% (25/63). Thus, in a large subpopulation of area LIP, a fairly precise alignment exists between sensory and motor fields.8. An additional set of 82 area LIP neurons were recorded while the monkey performed delayed saccades to 32 targets located on small, medium, and large imaginary circles. Preferred directions were calculated for each activity phase of each neuron, separately for each of the three circles. Preferred directions of the same phase were well aligned on the different circles. This observation supports the existence of direction preference, not strictly dependent on eccentricity. We also calculated alignment between different phases, separately for each circle. The distributions of alignments were similar, indicating that our results are not a peculiarity of the eccentricities used.9. The Post-S activity was not well aligned with the Pre-S phases. The distribution of alignments of the Post-S activity with the Pre-S phases was flat.10. We recorded 33 neurons while the monkey was performing back- and double-saccade paradigms. Neurons in LIP become active in anticipation of a saccade made into their motor field even if no visual stimulation has occurred in their receptive field, that is, these neurons code in motor coordinates.11. These characteristics of the activity in area LIP suggest that this cortical region is involved in the transformations of visual information for the planning of saccadic eye movements.