Lünenburger L, Kutz D F, Hoffmann K P
Department of Zoology and Neurobiology, Ruhr-University Bochum, D-44780 Bochum, Germany.
Eur J Neurosci. 2000 Nov;12(11):4107-16. doi: 10.1046/j.1460-9568.2000.00298.x.
When reaching for an object we usually look at it before we touch it with the hand. This often unconscious eye movement prior to the arm movement allows guiding of the final part of the hand trajectory by visual feedback. We examined the temporal and spatial coordination of this control system by psychophysical measurements of eye and arm movements of naive human subjects looking or looking and pointing as fast as possible to visual targets in physical and virtual-reality setups. The reaction times of saccades to a step-displaced target were reduced, and the number of corrective saccades decreased, when the subject had to produce a corresponding simultaneous hand movement to the same target. The saccadic reaction time was increased when saccade and hand movement went in opposite directions. In a double-step task the reaction time for the second saccade was longer than for the first. Co-use of the hand leads to an additional increase of saccadic reaction time. Taken together this study shows an improvement in initial saccades if they are accompanied by hand movements to the same target. This effect might ensure that the reach target is foveated early and accurately enough to support the visual feedback control of the hand near the target. Longer reaction times for the second saccade to double-step displaced targets might reflect a saccadic refractory time intensified by simultaneous arm movements. These results are discussed in the light of recent findings from our laboratory on saccade- and reach-related neurons in the superior colliculus of macaque monkeys.
当伸手去拿一个物体时，我们通常会在手部触碰之前先看向它。这种在手臂运动之前常常无意识的眼动，能通过视觉反馈对手部轨迹的最后部分进行引导。我们通过对天真的人类受试者在物理和虚拟现实环境中尽可能快速地看向或看向并指向视觉目标时的眼动和手臂运动进行心理物理学测量，来研究这个控制系统的时间和空间协调性。当受试者必须同时对手部进行相应的向同一目标的运动时，对阶跃位移目标的扫视反应时间缩短，且校正扫视的次数减少。当扫视和手部运动方向相反时，扫视反应时间会增加。在双步任务中，第二次扫视的反应时间比第一次长。手部的协同使用会导致扫视反应时间进一步增加。综合来看，这项研究表明，如果初始扫视伴随着向同一目标的手部运动，那么扫视会得到改善。这种效应可能确保足够早且准确地将目标中央凹对准，以支持目标附近手部的视觉反馈控制。对双步位移目标的第二次扫视反应时间更长，可能反映了同时进行的手臂运动会加剧扫视不应期。我们将根据本实验室最近在猕猴上丘中关于与扫视和伸手相关神经元的研究结果来讨论这些结果。
