Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri; and.
J Neurophysiol. 2013 Nov;110(10):2247-56. doi: 10.1152/jn.00968.2012. Epub 2013 Aug 21.
We often look at and sometimes reach for visible targets. Looking at a target is fast and relatively easy. By comparison, reaching for an object is slower and is associated with a larger cost. We hypothesized that, as a result of these differences, abrupt visual onsets may drive the circuits involved in saccade planning more directly and with less intermediate regulation than the circuits involved in reach planning. To test this hypothesis, we recorded discharge activity of neurons in the parietal oculomotor system (area LIP) and in the parietal somatomotor system (area PRR) while monkeys performed a visually guided movement task and a choice task. We found that in the visually guided movement task LIP neurons show a prominent transient response to target onset. PRR neurons also show a transient response, although this response is reduced in amplitude, is delayed, and has a slower rise time compared with LIP. A more striking difference is observed in the choice task. The transient response of PRR neurons is almost completely abolished and replaced with a slow buildup of activity, while the LIP response is merely delayed and reduced in amplitude. Our findings suggest that the oculomotor system is more closely and obligatorily coupled to the visual system, whereas the somatomotor system operates in a more discriminating manner.
我们经常观察并有时伸手去够可见的目标。观察目标既快捷又相对容易。相比之下，伸手去够物体则较慢，而且成本也更高。我们假设，由于这些差异，突然的视觉出现可能会比涉及伸手计划的电路更直接、更少有中间调节地驱动涉及眼球运动计划的电路。为了验证这一假设，我们在猴子执行视觉引导的运动任务和选择任务时，记录了顶叶眼球运动系统（LIP 区）和顶叶躯体运动系统（PRR 区）神经元的放电活动。我们发现，在视觉引导的运动任务中，LIP 神经元对目标出现有明显的短暂反应。PRR 神经元也显示出短暂的反应，尽管这种反应的幅度减小，延迟且上升时间较慢。在选择任务中观察到更明显的差异。PRR 神经元的瞬态反应几乎完全被消除，取而代之的是活动的缓慢积累，而 LIP 的反应仅被延迟且幅度减小。我们的发现表明，眼球运动系统与视觉系统的联系更加紧密和强制性，而躯体运动系统则以更具辨别力的方式运作。
