SACCADE-RELATED ACTIVITY IN THE LATERAL INTRAPARIETAL AREA .1. TEMPORAL PROPERTIES - COMPARISON WITH AREA 7A
SACCADE-RELATED ACTIVITY IN THE LATERAL INTRAPARIETAL AREA .1. TEMPORAL PROPERTIES - COMPARISON WITH AREA 7A
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DOI：
10.1152/jn.1991.66.3.1095
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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.顶叶下小叶（IPL）的皮质包含其活动与扫视眼球运动相关的神经元。然而，IPL在扫视中的确切作用仍然不清楚。在本文和配套论文中，我们通过量化眼跳相关（S）活动的许多空间和时间参数来解决这个问题。这些参数迄今为止在很大程度上没有研究过。记录了猕猴在执行延迟扫视任务时单个神经元的活动。这里提出的分析是基于161个神经元记录从外侧顶内区（LIP），最近定义的IPL的细分;和54个神经元记录从IPL的相邻部分，区域7A。共分离出409个IPL神经元.延迟扫视任务中IPL神经元的典型活动有三个基本阶段：光敏（LS）、记忆（M）和S。这些基本相位对于LIP和7a区的神经元是共同的。在每个阶段（LS，M和S），单个神经元可能是或可能不是活跃的。然而，大多数LIP神经元在不止一个阶段中活跃。为了比较不同神经元的活动水平，实际的放电率被每个神经元的背景水平加权，从而在任务的每个阶段产生每个神经元的“活动指数”。我们计算了LS和M阶段以及与扫视相关的三个阶段的活动指数：扫视前（Pre-S），扫视一致（S-Co）和扫视后（Post-S）阶段。对于LIP区神经元，LS、M、Pre-S和S-Co活动的活动指数中值较高，而在Post-S期间稍低。在7a区，LS期，尤其是M期和Pre-S期的中值较低，与扫视一致时稍高，扫视后较高。在LIP区，在每个时相，49-63%的神经元具有兴奋性反应，10-17%的神经元具有抑制性反应。与此相反，在7a区兴奋性反应最常见的后S期（56%）。兴奋在M（28%）和Pre-S（22%）期间特别罕见。抑制反应的发生率也不同（4-18%）。抑制的时间过程与兴奋的时间过程大致相反;抑制反应的最高频率发生在眼跳期间。7. S活动的潜伏期被定义为相对于扫视开始的时间，此时活动变得显著高于背景。在LIP区，潜伏期从扫视前200 ms到扫视后200 ms不等。扫视前LIP区的平均潜伏期为10.5 ms。在7a区，潜伏期范围从扫视前50 ms到扫视后380 ms。扫视后7a区的平均潜伏期为140 ms。如果一个神经元的活动在扫视开始时与背景有显著差异，则该神经元被认为是前扫视的。换句话说，神经元S活动的潜伏期必须小于或等于0 ms。在LIP区域，72%（61/85）的神经元是预跃的。在7a区，只有18%（6/33）的单位是前accadadic。扫视活动的偏移时间被定义为活动持续超过扫视的时间。S活动通常持续远远超过眼跳。LIP神经元的中位偏移时间为120 ms。7a神经元的中位偏移时间为300 ms（但请注意，大多数7a区神经元的S活动仅在囊后开始）。S活动的持续时间是根据其潜伏期和偏移量以及扫视运动的持续时间（通常为60 ms）计算的。对于两个区域LIP和7a，持续时间的分布近似为高斯分布。两个区域的分布参数值也相似（LIP和7a的中位数均为210 ms）。因此，S活动的持续时间通常比扫视本身的持续时间长得多。在LIP区，LS活动的起始潜伏期范围为50至270 ms，中位数为110 ms。在7a区，尽管范围与LIP相似，但LS潜伏期通常较长（中位数为160 ms）。总之，在LS、M和Pre-S期间，LIP区域包含预期扫视的剧烈活动。区域7a主要在扫视期间和之后活跃。这些结果表明，区域LIP参与规划的扫视。然而，7a区可能主要是为了满足不同的功能。
1. The cortex of the inferior parietal lobule (IPL) contains neurons whose activity is related to saccadic eye movements. The exact role of the IPL in relation to saccades remains, however, unclear. In this and the companion paper, we approach this problem by quantifying many of the spatial and temporal parameters of the saccade-related (S) activity. These parameters have hitherto been largely unstudied.2. The activity of single neurons was recorded from Macaca mulatta monkeys while they were performing a delayed-saccade task. The analysis presented here is based on 161 neurons recorded from the lateral intraparietal area (LIP), a recently defined subdivision of the IPL; and 54 neurons recorded from the neighboring part of the IPL, area 7a. Overall, 409 IPL neurons were isolated in this study.3. The typical activity of IPL neurons during the delayed-saccade task has three basic phases: light sensitive (LS), memory (M), and S. These basic phases are common to neurons of both areas LIP and 7a. In each phase (LS, M, and S), individual neurons may or may not be active. Most LIP neurons, however, are active in more than one phase.4. To compare the activity levels of different neurons, the actual firing rate was weighted by each neuron's background level, yielding an "activity index" for each neuron, in each phase of the task. We calculated the activity index for the LS and M phases and for three phases related to the saccade: a presaccadic (Pre-S), a saccade-coincident (S-Co), and a postsaccadic (Post-S) phase. For area LIP neurons the median values of the activity index were high for the LS, M, Pre-S, and S-Co activities, and slightly lower in the Post-S period. In area 7a the median values were low for the LS phase and, in particular, for the M and Pre-S phases, somewhat higher coincident with the saccade, and high post-saccadically.5. In area LIP, in each phase, 49-63% of the neurons had excitatory activity, and 10-17% had inhibitory responses.6. In contrast, in area 7a excitatory responses were most frequent in the Post-S phase (56%). Excitation was particularly infrequent during M (28%) and Pre-S (22%). The incidence of inhibitory responses varied too (4-18%). The time course of inhibition was roughly opposite that of excitation; the highest frequency of inhibitory responses occurred during the saccade.7. The latency of the S activity was defined as the time, relative to the beginning of the saccade, when the activity became significantly higher than background. In area LIP, latencies ranged from 200 ms before the saccade to 200 ms after the saccade. The mean latency in area LIP was 10.5 ms before the saccade. In area 7a the latencies ranged from 50 ms before the saccade to 380 ms after the saccade. The mean latency in area 7a was 140 ms after the saccade.8. A neuron was considered presaccadic if its activity varied significantly from background by the time the saccade started. In other words, the latency of the neuron's S activity had to be less-than-or-equal-to 0 ms. In area LIP, 72% (61/85) of the neurons were presaccadic. In area 7a, only 18% (6/33) of the units were presaccadic.9. The offset time of the saccadic activity was defined as the time the activity outlasted the saccade. The S activity usually lasted well beyond the saccade. The median offset time for LIP neurons was 120 ms. The median offset time for 7a neurons was 300 ms (but note that the S activity of most area 7a neurons only started postsaccadically).10. The duration of the S activity was computed from its latency and offset and from the duration of the saccadic movement (typically 60 ms). For both areas LIP and 7a the distribution of durations was approximately Gaussian. The parameter values of the distributions were also similar for both areas (median 210 ms in both LIP and 7a). Thus the duration of the S activity is usually considerably longer than the duration of the saccade itself.11. In area LIP the onset latencies of the LS activity ranged from 50 to 270 ms, with median 110 ms. In area 7a, although the range was similar to that of LIP, typically the LS latencies were longer (median 160 ms).12. In summary, area LIP contains vigorous activity in anticipation of the saccade, during the LS, M, and Pre-S periods. Area 7a is active mainly during and after the saccade. These results suggest that area LIP participates in the planning of saccades. Area 7a, however, probably primarily subserves different functions.