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猕猴外侧膝状核中运动规划与扫视后注视的相关性。

Correlates of motor planning and postsaccadic fixation in the macaque monkey lateral geniculate nucleus.

作者信息

Royal D W, Sáry Gy, Schall J D, Casagrande V A

机构信息

Center for Molecular Neuroscience, Vanderbilt University, Nashville, TN 37232-2175, USA.

出版信息

Exp Brain Res. 2006 Jan;168(1-2):62-75. doi: 10.1007/s00221-005-0093-z. Epub 2005 Sep 7.

Abstract

There is significant controversy regarding the ability of the primate visual system to construct stable percepts from a never-ending stream of brief fixations and rapid saccadic eye movements. In this study, we examined the timing and occurrence of perisaccadic modulation of LGN single-unit activity in awake-behaving macaque monkeys while they made spontaneous saccades in the dark and made visually guided saccades to discrete stimuli located outside the receptive field. Our hypothesis was that the activity of LGN cells is modulated by efference copies of motor plans to produce saccadic eye movements and that this modulation depends neither on the presence of feedforward visual information nor on a corollary discharge of signals directing saccadic eye movements. On average, 25% of LGN cells demonstrated significant perisaccadic modulation. This modulation consisted of a moderate suppression of activity that began more than 100 ms prior to the initiation of a saccadic eye movement and continued beyond the termination of the saccadic eye movement. This suppression was followed by a large enhancement of activity after the eyes arrived at the next fixation. Although members of all three LGN relay cell classes (magnocellular, parvocellular, and koniocellular) demonstrated significant saccade-related suppression and enhancement of activity, more cells demonstrated postsaccadic enhancement (25%) than perisaccadic suppression (17%). In no case did the timing of the modulation coincide directly with saccade duration. The degree of modulation observed did not vary with LGN cell class, LGN receptive field center location, center sign (ON-center or OFF-center), or saccade latency or velocity. The time course of modulation did, however, vary with saccade size such that suppression was longer for longer saccades. The fact that activity from a percentage of LGN cells from all cell classes was modulated in relationship to saccadic eye movements in the absence of direct visual stimulation suggests that this modulation is a general phenomenon not tied to specific types of visual stimuli. Similarly, because the onset of the modulation preceded eye movements by more than 100 ms, it is likely that this modulation reflects higher order motor-planning rather than a corollary of mechanisms in direct control of eye movements themselves. Finally, the fact that the largest modulation is a postsaccadic enhancement of activity may suggest that perisaccadic modulations are designed more for the facilitation of visual information processing once the eyes land at a new location than for filtering unwanted visual stimuli.

摘要

关于灵长类视觉系统能否从源源不断的短暂注视和快速扫视眼动中构建稳定感知,存在重大争议。在本研究中,我们在清醒行为的猕猴自发于黑暗中进行扫视以及对位于感受野之外的离散刺激进行视觉引导扫视时,研究了外侧膝状体(LGN)单个神经元活动的扫视周边调制的时间和发生情况。我们的假设是,LGN细胞的活动受运动计划的传出副本调制,以产生扫视眼动,并且这种调制既不依赖于前馈视觉信息的存在,也不依赖于引导扫视眼动的信号的伴随放电。平均而言,25%的LGN细胞表现出显著的扫视周边调制。这种调制包括在扫视眼动开始前100多毫秒开始并持续到扫视眼动结束后的适度活动抑制。这种抑制之后是眼睛到达下一个注视点后活动的大幅增强。虽然所有三种LGN中继细胞类别(大细胞、小细胞和异细胞)的成员都表现出与扫视相关的活动抑制和增强,但表现出扫视后增强(25%)的细胞比扫视周边抑制(17%)的细胞更多。在任何情况下,调制的时间都不与扫视持续时间直接一致。观察到的调制程度不随LGN细胞类别、LGN感受野中心位置、中心信号(ON中心或OFF中心)、扫视潜伏期或速度而变化。然而,调制的时间进程确实随扫视大小而变化,使得较长扫视的抑制时间更长。在没有直接视觉刺激的情况下,所有细胞类别的一定比例的LGN细胞的活动与扫视眼动相关地受到调制,这一事实表明这种调制是一种普遍现象,与特定类型的视觉刺激无关。同样,由于调制的开始比眼动提前100多毫秒,很可能这种调制反映的是更高层次的运动计划,而不是直接控制眼动本身的机制的伴随现象。最后,最大的调制是扫视后活动增强这一事实可能表明,扫视周边调制更多地是为了便于眼睛落在新位置后进行视觉信息处理,而不是为了过滤不需要的视觉刺激。

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