Saul Alan B
Department of Ophthalmology, Medical College of Georgia, Augusta, Georgia 30912, USA.
Vis Neurosci. 2010 Nov;27(5-6):171-81. doi: 10.1017/S0952523810000258. Epub 2010 Oct 8.
Even during active fixation, small eye movements persist that might be expected to interfere with vision. Numerous brain mechanisms probably contribute to discounting this jitter. Changes in the timing of responses in the visual thalamus associated with fixational saccades are considered in this study. Activity of single neurons in alert monkey lateral geniculate nucleus (LGN) was recorded during fixation while pseudorandom visual noise stimuli were presented. The position of the stimulus on the display monitor was adjusted based on eye position measurements to control for changes in retinal locations due to eye movements. A method for extracting nonstationary first-order response mechanisms was applied, so that changes around the times of saccades could be observed. Saccade-related changes were seen in both amplitude and timing of geniculate responses. Amplitudes were greatly reduced around saccades. Timing was retarded slightly during a window of about 200 ms around saccades. That is, responses became more sustained. These effects were found in both parvocellular and magnocellular neurons. Timing changes in LGN might play a role in maintaining cortical responses to visual stimuli in the presence of eye movements, compensating for the spatial shifts caused by saccades via these shifts in timing.
即使在主动注视过程中,仍会存在一些小的眼球运动,这些运动可能会干扰视觉。众多大脑机制可能有助于忽略这种抖动。本研究探讨了与注视性扫视相关的视觉丘脑反应时间的变化。在清醒猴子的外侧膝状体核(LGN)中,记录单个神经元在注视期间的活动,同时呈现伪随机视觉噪声刺激。根据眼球位置测量结果调整显示监视器上刺激的位置,以控制由于眼球运动导致的视网膜位置变化。应用了一种提取非平稳一阶反应机制的方法,以便观察扫视前后的变化。在膝状体反应的幅度和时间上都观察到了与扫视相关的变化。在扫视期间,幅度大幅降低。在扫视前后约200毫秒的窗口内,时间略有延迟。也就是说,反应变得更加持续。在小细胞和大细胞神经元中均发现了这些效应。LGN中的时间变化可能在眼球运动存在的情况下维持皮层对视觉刺激的反应中发挥作用,通过这些时间上的变化来补偿扫视引起的空间位移。